Ecs C_prog Material

8/9/2019 Ecs C_prog Material

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PROGRAMMING IN C

Staff Handled By : D.Mythili


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PROGRAMMING IN C

SYLLABUS

Unit-I

Structure of a C program C character set Delimiters Keywords identifiers Constants variables rules for definingVariables data types Declaring and initializing variables typeConversion. Operators and expressions

Unit-II

Formatted and Unformatted Input and output functions Decision Statements loop Control Statements.

Unit-III

Arrays : Array initialization definition characteristics- one dimensional array, predefined streams- Two- dimensional array Three or multi dimensional arrays. Strings and Standard functions:-Declaration and initialization of string- Display of string with differentformats String standard functions Application of strings. Pointers:Features, Pointer declaration, Arithmetic Operations with pointers-Pointers and Array Pointers and Two-dimensional array Array of

pointers Pointers to pointers Pointer and Strings Void pointers.Functions: Definition, Declaration, The return statement, Types offunctions, Call by value and Call by reference, Functions returningmore values, Functions as an argument. Functions with Arrays andpointers Recursion Preprocessor Directives.

Unit-IV

Structure and Union: Features of structure, Declaration andinitialization of structure, Structure within structure, Array of structure,Pointer to structure, Bit fields, Union.

Unit-V

Files: Streams and file types, Steps for file operation, File I/O,Structures read and write, other file functions, Command linearguments, I/O redirection


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DEPARTMENT OF ELECTRONICS AND COMMUNICATIONSYSTEM

STUDY MATERIAL

COURSE : II YEAR A, B.Sc ECSSEMESTER : IIIUNIT : ISUBJECT NAME : PROGRAMMING IN CLECTURER NAME : D.MYTHILINUMBER OF PAGES : 18DATE OF ISSUE :

Unit-IIntroduction to C programming - Structure of a C program C characterset Delimiters Keywords identifiers Constants variables rules

for defining Variables data types Declaring and initializing variables type Conversion. Operators and expressions

Introduction to C programmingC was an offspring of Basic Combined Programming

Language(bcpl) called B, developed in the 1960s at Cambridgeuniversity. B language was modified by Dennis Ritchie and wasimplemented at Bell Laboratories in 1972.The new language wasnamed as C. since it was developed along with UNIX operatingsystem, it is strongly associated with UNIX. It can run undervarious operating systems including MSDOS.

Importance of C:1. It is robust language.2. Rich set of built-in functions and operators are available.3. Easy to create complex programs.4. Suitable to write both application software as well as systemsoftware.5. It is highly portable. Because C programs written for onecomputer

can be run on another with little or no modification.6. It is well suited for structured programming. So that it is easy to

debug, test and maintain a module.7. It can extend itself.

Basic structure of C programming:

Documentation sectionlink section


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Definition sectionGlobal declaration sectionMain( ) function section{

declaration part

executable part

}

Subprogram sectionfunction 1function 2function 3

.

.function n

a) Include header file section:A C program depends upon some header files for function

definition that are used in the program. Each header file has .hextension. Eg. #include b) Global declaration:

This section declares some variables that are used in morethan one function. These variables are known as global variables. Thissection must be declared outside of all the functions.

c) Function main ( ): Every program in C must contain main ( ) function. Emptyparenthesis after main is necessary. The function main ( ) is a startingpoint of every C program. The execution of the program always beginswith the function main ( ).d) Declaration Part:

It declares the entire variables that are used in theexecutable part. Initializations of variables are also done in thissection. Initialization means providing initial value to the variables.e) Executable Part:

This part contains the statement following the declarations

of the variables. This part contains a set of statements or a singlestatement. These statements are enclosed between braces.f) User-defined function:

The functions defined by the user are called user-definedfunctions. These functions are generally defined after the main ( )function. They can be also be defined before main ( ) function. Thisportion is not compulsory.g) Comments:


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It is not compulsory in a program. However to understandthe flow of a program, the programmer can include comments in theprogram. Comments can be inserted by the programmer. These areuseful for documentation. The clarity of the program can be followed ifit is properly documented.

Example/ * This is a single comment * // * This is an example of / * nested comments * / * // * This is an example ofcomments with multiple lines * / / * It can be nested * /C Character Set The characters are used to form words, numbers andexpressions depending upon the computer on which the program runs.The characters in C are classified into the following characteristics.1. Letters 2. Digits 3. White Spaces 4. Special characters.

Character Set

1) Letters 2) Digits 3) WhiteSpaces

Capital A toZ

All decimal digits 0 to 9 Blank Space

Small a to z Horizontal TabVertical TabNew LineForm Feed

4) Special Characters:

, Comma & Ampersand. Period or dot ^ Caret; Semi colon * Asterisk: Colon - Minus` Apostrophe + Plus Quotation

mark< Less than

! Exclamationmark

> Greater than

Vertical bar ()

Parenthesis left /right

/ Slash []

Bracket left /right

\ Back slash {}

Braces left / right

~ Tilde % Percent_ Under score # Number sign or

hash$ Dollar = Equal to


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? Questionmark

@ At the rate

Delimiters:Language pattern of C uses special kinds of symbols, which are

called as delimiters. They are given as under.

Delimiters Use: Colon Useful for label; Semi Colon Terminates statement( )Parenthesis

Used in expression andfunction

[ ] Squarebracket

Used for arraydeclaration

{ } Curlybrace

Scope of statement

# Hash Preprocessor directive, Comma Variable separator

The C keywords:The C keywords are reserved words by a compiler. They are

assigned a fixed meaning. The keywords cannot be used as variablenames because they have been assigned fixed jobs. However, fewcompilers allow to construct a variable name, which exactly coincideswith the keywords. For utilizing the keywords in a program no headerfile is to be included. The description of the keywords is given below.

auto double

int struct

break else long switchcase enu

m

regist

er

typede

fchar exter

nreturn

union

const float short unsigned

continue

for signed

void

default

goto sizeof volatile

do if static whileAdditional keywords for

Borland Casm if static while

Identifiers:Identifiers are names of variables, functions and arrays. They

are user-defined names, consisting of sequence of letters and digits,with the letter as the first character. Lower case letters are preferred.However, the upper case letters also permitted. The underscore ( _ )


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symbol can be used as an identifier.Example: 1. #define N 10

2. #define a 15Here N and a are user-defined identifiers.

Constants: The constants in C are applicable to the values that do notchange during the execution of a program. There are several types ofconstants in C. They are classified as follows.

A. Numerical constants:1) Integer constants:It refers to a sequence of digits from 0 to 9 without decimal

points or fractional part or other symbols. It requires minimum twobytes and maximum 4 bytes. Integer constants can either bepositive, negative or maybe zero. The number without a sign isassumed as positive.Example: 10, 20, +30, -152) Real constants:The numbers with fractional part is called real or floating-pointconstants. Many parameters or quantities are defined not only inintegers but also in real numbers.Example: 1) 54.98

2) 25.75

B. Character constants:1. Single character constants:

A character constant is a single character. They are alsorepresented with a single digit or a single special symbol or whitespace enclosed within a pair of single quote marks.Examples: 1) a

2) #3) 2


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4) 2. String Constants:

They are a sequence of characters enclosed within a doublequote marks. The string may be a combination of all kinds ofsymbols.

Example: Hello, India, 444, a.

Variables:A variable is a data name that may be used to hold a data

value. A variable may take different values at different timesduring the program execution.

Rules for forming a variable:1. The starting character should be a letter. The first character may be

followed by a sequence of letters or digits.2. The maximum number of characters in a variable may be 8

characters. The number of characters differs from compiler tocompiler.3. Upper and lower case are significant. Example: TOTAL is notsame as total or Total.4. The variable should not be a keyword.5. White space is not allowed.6. Special characters except _(underscore) symbol are notallowed.

C Data Types:Data is a collection of characters, digits, symbols etc., the

data are used to represent information. The data are classified invarious types. C data types are classified into the followingcategories.a. Basic data typeb. Derived data typec. User-defined data typed. Void data type


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Basic Data types:The basic data types supported by C are described with their size

in bytes and ranges.Data Type Size in

BytesRange

char 1 -128 to 127unsignedchar

1 0 to 255

signed char 1 -128 to 127Int 2 - 32768 to 32767unsigned int 2 0 to 65535signed int 2 - 32768 to 32767

short int 2 - 32768 to 32767unsignedshort int

2 0 to 65535

signed shortint

2 - 32768 to 32767

long int 4 - 2147483648 to2147483647

signed longint

4 - 2147483648 to2147483647

unsignedlong int

4 0 to 4294967295

float 4 3.4E- 38 to 3.4E+38double 8 1.7E 308 to 1.7E +

308long double 10 3.4E 4932 to 1.1E

+4932enum 2 - 32768 to 32767

Derived Data type:


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The derived data types are of the following types:1. Pointers2. Functions3. Arrays1. Pointers:

A pointer is a memory variable that stores a memory address.Pointers can have any name that is legal for other variables and itis declared in the same fashion like other variables but it is alwaysdenoted by * operator.int *x;float *f;char *y;

In the first statement x is an integer pointer that tells tothe compiler that it holds the address of any integer variable. Inthe same way f is a float pointer that stores the address of anyfloat variable and y is a character pointer that stores the address

of any character variable.2. Functions:A function is a self-contained block or a sub-program of one ormore statements that perform a special task when called. In figfunA( ) and funB( ) are two user-defined functions. These areinvoked from the body of main. After execution of funA( ) andfunB( ) the program control returns back to the calling functionmain( ).

3. ArraysAn array is a collection of elements of similar data types in

which each element is located in separate memory location.Eg. int b[4];Variables:

A variable is a data name that may be used to hold a datavalue. A variable may take different values at different timesduring the program execution.Rules for forming a variable:

1.The starting character should be a letter.


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2.The maximum number of characters may be 8 characters. itdiffers

3.Upper and lower case are significant. Example: TOTAL is notsame as total or Total.

4.The variable should not be a keyword.

5.White space is not allowed.6.Special characters except _(underscore) symbol is notallowed.

Valid examples:1. john2. value3. tot_amt4. a1

Invalid examples: Reason

1. 1868 1) The first letter should be a letter2. (area) 2) Special characters notallowed3. 27th 3) Number should not be afirst character4. % 4) Special characters not allowedData types:1. Primary data types.2. User- defined data type3. Derived data type

4. empty data set

Primary data types:1. Integral type:

a. Integer sizei. signed int 16 bitsii.short signed int 8 bitsiii.long signed int 32 bitsiv.unsigned int 16 bitsv.unsigned short int 8 bitsvi.unsigned long int 32 bits

b. Characteri. signed char 8 bitsii. unsigned char 8 bits

2. Floating-point typei. float 32 bitsii. double 64 bits


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iii. long double 80 bits

Declaration of variables:Purpose:1. It tells the compiler what the variable name is.

2. It specifies what type of data the variable will hold.

Syntax:

v1,v2,v3.vn- variables

Example:1. int count;2. int a,b;

3. float area,volume;4. char array;5. double a1;

data type keyword equivalent character charunsigned character unsigned charsigned character signed charsigned integer signed int to intsigned short integer signed short intsigned long integer signed ling int

unsigned integer unsigned int or unsigned intunsigned short integer unsigned short intunsigned long integer unsigned long intfloating point floatdouble precision doubleextended double precision long double

User defined declaration:Types:1. type definition2. enumerated data type

Type definition:Purpose:This allows the user to define the identifier that would representan existing data type. The user-defined type is later used todeclare variables.General form:


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Typedef - keyword Type - exiting data typeIdentifier new name given to the data type

Typedef cannot create a new type. Using identifier the variablescan be declared using the following syntax:

Examples:Typedef int units;Units batch1,batch2;Units name[10],name1[20];

Enumerated data type:

It is defined as follows

It is used to declare the variables that can have one of the valuesenclosed within braces(known as enumerated constants).we candeclare variables to be of this new type as below:

The enumerated variables v1,v2,vn can have one of the

values value1,value2,value n.Examples:

1. enum day {monday,tuesday,sunday};enum day week_beg,week_end;we can assign values like

2. week_beg=sunday;week_end=saturday;We can compare the values like

3.if (week_beg == friday)week_end=thursday;

The compiler automatically assigns integer digits beginning

with 0 to all the enumeration constants. Thus the enumerationconstants assign value1 as 0,value2 as 1 and so on. However theautomatic assignments can be overridden by assigning valuesexplicitly to the enumeration constants.Example:

enum day {monday=1,tuesday=5,.sunday};In the above Wednesday will take the value of 6,Thursday willtake 7 and so on.


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enummonth(Jan,Feb,Mar.Apr,May.Jun,Jul,Aug,Sep,Oct,Nov,Dec)this statement creates user defined data type. the keyword enum isfollowed by the tag name month. The enumerators are the identifiers Jan,Feb,Mar.Apr,May.Jun,Jul,Aug,Sep,Oct,Nov,Dec. Their values are

constant unsigned integers and start from 0. the identifier jan refers to0, feb to 1 and so on. The identifiers are not to be enclosed with inquotation marks.Write a program to create enumerated data type for 12months. Display their values in integer constants.#include #include Void main(){enum month(Jan,Feb,Mar.Apr,May.Jun,Jul,Aug,Sep,Oct,Nov,Dec);clrscr();

printf(\nJan=%d,Jan);printf(\nFeb=%d,Feb);printf(\nJune=%d,June);printf(\nDec=%d,Dec);}

OUTPUT:Jan=0Feb=1June=5Dec=11

Explanation: In the above program enumerated data type month isdeclared with 12-month names within two curly braces. The compilerassign 0 value to first identifier and 11 to last identifier. Using printf()statement the constants are displayed for different identifier. Bydefault the compiler assign value from 0 onwards. Instead of 0 theprogrammer can initialize his/her own constant to each identifier.

Global and local variables:Global variable is visible to all functions in the file. It is necessaryto declare the variable before the main function. No need todeclare the global variables in all functions. It is also known

external variable. Local variable is visible and meaningful onlyinside the function in which they are declared.Example:

/*example of storage classes*/int m;main( ){

int I;


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float balance;....function1( );

}

function1( ){int i;float sum;

}

Storage classes:Purpose:It provides the information about location and visibility of

variables.

Types meaning1. auto local variable known only to the functionwhere it is declared

default is auto.2.static local variable which exists and retains it svalue even after

control is transferred to the calling function.3.extern global variable known to all function sin the file4.register local variable which is stored in the register.

Example:auto int count;register char ch;static int x;extern long total;

Assignment statement:Purpose : values can be assigned to variables using the

assignment operator = as follows

Examples:


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It is possible to assign the values during declaration time asfollows:

Example:

Declaring a variable as Constant :Purpose :

To maintain the value of variable throughout the programexecution we are declaring the variable as constant.Example:

Reading the data from the keyboard:Another way of giving values to variables is to input data

through keyboard using the scanf function.Syntax:

The control string contains the format of data beingreceived. The ampersand symbol & before the variable name isan operator that specifies the variable names addressExample :

%d- represents integer value%f- float number%c- character

%lf - double%u - unsigned int

Output using printf:Purpose :

It is used to display the output as well as to create aninteractive program .Syntax:


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Operators :Purpose :

It is used to tell the computer to manipulate dataand variables.Types:

1. Arithmetic operators2. Relational operators

3. Logical operators4. Assignment operators5. Increment and decrement operators6. Conditional operators7. Bitwise operators8. Special operators

Arithmetic operators:

Arithmetic operators are used to perform arithmeticoperations like addition , subtraction, multiplication and divisionand to find the remaindering division. The corresponding symbolsare +(addition or unary plus),- (subtraction or unary minus),*,/,%(modulo division).C does not have an operator exponentiation.

Relational operators:Purpose:

To relate any two or more quantities.

Operator Meaning< is less than> is greater than

> is greater than orequal to


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to this c hasshorthand operators.

Syntax:

Statement with simple Statementwith short

Assignment operator. Handoperator.

a=a+1 a+=1a=a-1 a-=1a=a*1 a*=1a=a/1 a/=1a=a%b a%=b

Advantages: 1. No need to repeat the operator again in the righthand side.

2. The statement is more concise and clear.3. The statement is more efficient.4. It is easy to read.

Increment and Decrement operators:Purpose:

To decrement the value of the variable by one or toincrement the value of the variable by one.

Operators:++ - adds 1 to the operand-- - subtracts 1 unary operators

Example:++m; (++ used as prefix operator)m++; (++ as postfix operator)If they are used independently then meaning is same.

Consider the followingm=5;y=++m;In the above case m and y would be 6.

m=5;y=m++;

In the above case m would be 6 and y would be 5.Similarly for the --operator.

Conditional operator:Purpose:

A ternary operator pair ?: is used to construct


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conditional expressionsSyntax:

Example :x=(a>b)?a:b;In the above the condition is evaluated first .if true

then a will be assigned to x or else b will be assigned to x. Theabove syntax is equivalent to if else statement.

Bitwise operators:Purpose:

Manipulating the data at bit level.

Operator Meaning

& bitwise AND| bitwise OR^ bitwise EXCLUSIVE OR> shift right~ ones complement

Special operators:sizeof - to determine the size of the variable,(comma) - to link the related expressions togetherexample : value=(x=10,y=17,x+y)

. and -> - member selection operator& and * - pointer operator

Expressions:Combination of both operand and operator.

Types:1. Arithmetic2. Relational3. Logical

Arithmetic expression:

Operand combined with arithmetic operators called asarithmetic expressions

Examples:a+bc-d

Types:1. Integer arithmetic2. Real arithmetic


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3. Mixed arithmetic Integer arithmetic:

Arithmetic operator combined with integer operands. Example:

a + b; where a and b are of type integer.

Real arithmetic:Arithmetic operator combined with real operands.

Example:a + b where a and b are of type real.

Mixed mode arithmetic:Expression consists of both integer and real operands.

Example:a-b where a is of type integer and b is of type real.

Evaluation of expression:Expression evaluation based on the priority of

operators.High priority * / % left to rightLow priority + -

Logical expression:

Whenever the logical operators combine any two relationalexpressions then it is called logical expression.

Example:((ad))

Operator precedence:1. Logical NOT2. Logical AND3. Logical OR

Type conversions in expressions:If operands are of different types then the lower type

is automatically converted into higher type before the operationproceeds. The result is of higher type.1. All short and char to int.

2. If one of the operand is long double then other will beconverted into long double.3. Else if one is double then other will be converted into double.4. Else if one is float then other will be float.5. Else if one is unsigned long int then other will be unsigned longint.6. If one is unsigned long int and other one is long int then

a. Unsigned long int will be converted into long int or


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b. Long int will be converted into unsigned long int.

Casting a value:If we need to force the type conversion explicitly then

it is called as coercion.

Example: ratio=(float) number1/number2;Where number 1 and number2 are of type integer type,

ratio is of type float. General form of Casting:

Suggested Questions

3. What are unary operators?4. Give an example for short hand assignment operator.5. Where was C orginally developed and by whom?6. What is the name for data type conversion?7. Explain about mixed mode arithmetic operations8. Write short notes on logical operators.9. Explain about operators supported by C10.Explain data types supported by C11.Give the hierarchy of operator precendences covering all of the

operators in C12.Explain arithmetic & relational operators?

13.Explain Structure of C Program with suitable examples.14.What is variables. List out the rules to declare a variables.15.What is Identifiers.16.What is type casting.17.Write a program Which combine all the operators.


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STUDY MATERIAL

COURSE : II YEAR A, B.Sc ECSSEMESTER : IIIUNIT : II

SUBJECT NAME : PROGRAMMING IN CLECTURER NAME : D.MYTHILINUMBER OF PAGES : 7DATE OF ISSUE :

Unit-II

Decision Statements loop Control Statements.

Control/Decision making statements:

1.If statement2.Switch statement3.Conditional operator statement4.Goto statement

If statement:Purpose:

It is a powerful decision making statement to controlthe flow of execution. It is basically two-way decision statementand is used in conjunction with and expression. Syntax:

It allows the system to evaluate the expression firstand then, depending on whether the value is true or false ittransfers the Control to the particular statement.

entry

false

true

Different forms of IF statement:1. Simple if statement


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2. If else statement3. Nested if else statement4. Else if ladder

Simple if statement:

Syntax:

In the above statement if test expression is true thenstatement block

will be executed else statement block will be skipped.

If else statement:

Syntax:

Above statement if the test expression is true then true blockstatement, immediately following by the If statement areexecuted; otherwise the false block statement are executed. Ineither case either true block will be executed or false block will beexecuted but not both.

Nesting of if else statement:Syntax:


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In the above statement if the condition 1 is true then thesecond if condition 2 will be tested and if it is also true then thestatement 1 will be executed. if the second condition is false thenthe statement 2 will be executed. If the first condition is false thenthe statement 3 will be executed.

Else if ladder:Syntax:

The condition are evaluated from the top to bottom as soon as atrue condition is found, the statement associated with it isexecuted and the control is transferred to the statement x. Whenall the n conditions become false then the final else containingthe default-statement will be executed.

The Switch statement:Purpose:

Using the value of any variable or expression uses it to selectone branch among several alternatives. The switch tests the value

of given variable (or) expression against a list of case values andwhen a match is found, a block of statements associated with thatcase is executed. Syntax:


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In the above syntax the expression is an integer expressionor characters the value-1,value-2,. are constants or constantexpressions and are known as case labels.

Each of these values should be unique within a switchstatement. block-1, block-2,.. are statements contain zero ormore statements. There is no need to put braces around theseblocks. The case labels must end with a colon. When a switch is

executed, the value of expression is compared with case values, ifmatches, then the block of statements that follows the case areexecuted. The break statement is used to exit from the switchstatement.Example:--------------------switch(n){

case 1: c=a+b;break;

case 2: c=a-b;break;

default: c=a/b;break;

}printf(%d,c);----------------------------------

Loop constructs:Purpose:

It is used to repeat the block of statements for n number oftimes.Process involved in looping statement is as follows:-

1. Setting and initialization of counter.2. Execution of the statements of the statements in the loop.3. Test for a specified condition for execution of the loop.4. Incrementing the counter.


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Types:1. While statement2. Do statement3. For statement

1) While statement:a. The while is an entry- controlled loop statement.b. The test -condition is evaluated first and if thecondition is true, then the body of

loop is executed. Again the test-condition is tested and bodyof the loop will be

repeated until the condition becomes falsec. If at the entry condition itself the test-condition is false thenbody of loop will beskipped.Syntax:

Example:#include < stdio.h>void main(){

int i=1;while (i


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-----------------------------------do{

printf(well done!);

}while(number


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for (i=1;i


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24.What sre symbols used for logical operators AND & OR?25.Give the conversion specifications used for printing octal & hexa

decimal values.26.every line in c programming should end with a semi colon.- say

true or false

27.in c language , lowercase letters are significant- say true or false28.every c program end with and END word.29.main() is where the program begins its execution.30.a line in c program may have more than oneline of output.31.a printf() statement can generate only one line of output.32.syntax error will be detected by the compiler.33.what are trigraph characters? How are they useful?34.what is variable.35.what is initialization? Why it is important?36.what are enumeration variables? How are they declared?37.describe the purpose of the qualifiers const and volatile.

38.which of the following are invalid constant and why?0.00015x1.59999912.34239.which of the following are invalid variable names and why?MaximumLast.rollnoMn+meRow total40.which of the following arithmetic expressions are valid? If invalid,

give reason.25/3%212.4%221 %(int)3.241.write the c assignment statements to evaluate the following

equations.42.Area= IIr2+22/7rh43.Torque=2m1m2

44.m1+m245.determine the valueof each of the following logical expressions if

a=10,b=25and c=-7a>b&&a12&&c


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48.write the syntax of if.. statement . write the difference betweenwhile statement and dowhile statement

Suggested Questions:49.Explain if statement with an example

50.Differentiate while & do...while statement51.?52.write a program to check whether the given year is a leap year

or not53.write a program to find largest among three given numbers.54.write a program to find reverse of the given digit55.write a program to do arithmetic operations for any two given

numbers using switch case statement.56.write important features of for statement.57.write a program to convert the given farenheit temperature to

Celsius temperature.

58.write a program to generate fibanocci numbers59.write a program to generate prime numbers.60.write a program to calculate simple and compound interest

Essay Answers61.Explain about looping statements with suitable examples62.Write a program to print the fibonacci series63.Write a program to print the prime numbers between 1 to 10064.Write a program in c to solve a quadratic equation to check all

possibilities of their coefficients

STUDY MATERIAL

COURSE : II YEAR A, B.Sc ECSSEMESTER : IIIUNIT : IIISUBJECT NAME : PROGRAMMING IN CLECTURER NAME : D.MYTHILINUMBER OF PAGES : 56DATE OF ISSUE :

Unit-IIIArrays : Array initialization definition characteristics- one dimensional array, predefined streams- Two- dimensional array Threeor multi dimensional arrays. Strings and Standard functions:-Declaration and initialization of string- Display of string with differentformats String standard functions Application of strings. Pointers:Features, Pointer declaration, Arithmetic Operations with pointers-


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Pointers and Array Pointers and Two-dimensional array Array ofpointers Pointers to pointers Pointer and Strings Void pointers.Functions: Definition, Declaration, The return statement, Types offunctions, Call by value and Call by reference, Functions returningmore values, Functions as an argument. Functions with Arrays and

pointers Recursion Preprocessor Directives.

ARRAYSDefinition :An array is a group of related data items that share a common name.Example:An array name salarycan be used to represent a set of salaries of agroup of employees.A particular value in an array is called an element and can be writtenas follows

salary [10] represents the salary of the 10th person.

TYPES :1. One dimensional arrays / Single subscripted array2. Two dimensional array3. Multi dimensional array

ONE DIMENSIONAL ARRAY:Definition :

A list of related data items with one variable and only one subscript iscalled single- subscripted array.

DECLARATION OF ARRAYS:Syntax:

wheretype - int, float ,double, longint,char

variable_name - valid c programming variablesize - no. of elements

Example:1. int a[10];2. float height[20];3. char name[10];

Explanation:1. In the first declaration we can store atmost 10 elements


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of type integers.2. The second declaration can hold 20 elements of realnumbers.3. In third we can store atmost 9 characters. Whiledeclaring character array the last character must be a null

character(\0). This character is automatically included while assigningvalues to these variables. While mentioning about the size we mustinclude one extra space with maximum number of characters.

INITIALIZATION OF ARRAYS: Syntax:

We can initialize the array variable like ordinary variableswhen they are declared. In the above list of values are separated by

comma. Suppose the value is not given then automatically it will beassigned as zero.

Example:a. static float total[5] = {0.5,15.63,-20};

In the above the first three elements are set to 0.5, 15.63, -20and the remaining elements are set to

zero.b. static int count[]= {1,1,1,1};

In the above the size is omitted. The compiler itself allocatesenough space for all initialized

elements.

DRAW BACKS IN INITIALIZATION OF ARRAYS:

1. There is no convenient way to initialize only selectedelements.2. There is no shortcut method for initializing a large numberof array elements like the one available in FORTRAN.

TWO DIMENSIONAL ARRAYS: Definition :

A list of related data items withone variable and subscriptsrepresenting the row value and column value is called two dimensionalarray.



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wheretype - int, float ,double, longint,charvariable_name - valid c programming

variablesize - no. of elements

Example:1. int a[10][10];2. float height[20][2];3. char name[10][10];

Explanation:1. In the first declaration we can store atmost 100 elements ofintegers.2. The second declaration can hold 40 elements of real numbers.3. In third we can store almost 10 names of 9 characters. While

declaring character array the last character must be a nullcharacter(\0). This character is automatically included while assigningvalues to these variables. While mentioning about the size we mustinclude on extra space with maximum number of characters.

INITIALIZATION OF ARRAYS:Syntax:

We can initialize the array variable like ordinary variables when

they are declared. In the above list of values are separated by comma.Suppose the value is not given then automatically it will be assigned aszero.

Example:

a. static float mat[2][3] = {{0.5,15.63,-20},{10.2}};In the above the first row elements are set to 0.5 , 15.63 , -20 and inthe second row the first element is 10.2 and the remaining elementsare set to zero.

MULTI DIMENSIONAL ARRAYS: Definition :

A list of related data items with one variable and more than 2two subscripts is called multi-dimensional array.



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wheretype -- int , float , double , longint , char

array_name -- valid c programming variable

si -- size of ith dimension where i =1,2,3n

SAMPLE PROGRAM USING ARRAY:(ascending order)

#include #include main(){

int i, a[10], n, t;/*INPUT THE NUMBER OF ELEMENTS*/

printf(Enter the total no of elements \n);scanf(%d,&n);/*ENTER THE VALUES TO BE SORTED*/printf(Enter elements \n);for(i=1;i


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Definition:String is an array of characters. Any group of characters

enclosed between double quotes is a string constant.Example:

Where there is will there is way

Operations performed on strings:1. Reading and writing strings.2. Combining strings together.3. Copying one string to another.4. Comparing strings for equality.

5. Extracting a portion of string.

DECLARATION AND INITIALIZATION OF STRING VARIABLES:Syntax:

Example:1. char city[10];2. char name[30];3. static char city[9]= new york;4. static char city[9]={n,e,w,,,y,o,r,k,\o};

In the above 3 and 4 initializations are same. In character array thecompiler automatically includes the null character at the end of thestring.

If the size is not mentioned then the compiler itself defines the size ofthe array variable depending upon number of elements in theinitialization statement.

READING STRINGS FROM THE TERMINAL:The scanf function can be used with the control string %s

to read in a string of characters.

Example:char name[15];

scanf(% s,name);

In the above example & is not required before the variable name.

Drawback:1. We cannot read a line of text from the terminal.

Reading a line of text:We can read the entire line of text using the function getchar().

By using the above function it terminates the input process whenever


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it receives the newline character.

Example:/**************************************//* program to read a line of text from terminal*/

/**************************************/#include main(){char line[81],character;

int c;c=0;

printf(enter text .press at end\n);do{

character=getchar();

line[c]=character;c++;}while (character!=\n);

c=c-1;line[c]=\0;printf(\n%s\n,line);}

WRITING STRINGS TO THE SCREEN:Printf statement with control string %s is used to display the

string value.Example:

Printf(%s,name); (or) printf(%Total columns.Totalcharacters s,name);

EFFECT OF VARIOUS %S SPECIFICATION :1. When the field width is less than the length of the string , theentire string is printed.2. The integer value on the right side of the decimal pointspecifies the number of number of characters to be printed.3. When the number of characters to be printed is specified as

zero, nothing is printed.4. The minus sign in the specification causes the string to beprinted left- justified.

ARITHMETIC OPERATIONS ON CHARACTERS:C allows us to manipulate the characters in the same way as numbers.Whenever a character constant or character variable is used it isautomatically converted into integer value by the system. The integer


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value depends on the local character set of the system.Example:X=a;Printf(%d\n,x);

The output of the above statement will be 97.

Similarly it is also possible to perform all the arithmetic operations likeaddition ,subtraction , multiplication , division etc. To convert integerto ascii as well as ASCII to integer is done by using library functionslike itoa(integer),atoi(string).

PUTTING STRINGS TOGETHER: Just as we cannot assign one string another directly, we cannot jointwo strings together by the simple arithmetic addition like as follows:

Str3=str1+str2;

Str2=str1+good; invalid

The characters from str1 and str2 should be copied into thestr3 one after another. The size of the array str3 should be largeenough to hold the total characters. Example:

PROGRAM FOR CONCATENATION OF TWO STRINGS:#include

#include #include main( )

{int i , j , k;static char f_str[10]={hello};static char s_str[10]={world};char t_str[20];for(i=0;f_str[i]!=/0;i++)

t_str[i]=f_str[i];t_str= ;for(j=0;s_str[j]!=/0;j++)

t_str[i+j+1]=s_str[j];t_str[i+j+1]= ;

printf(%s,t_Str);}Output:

hello worldSTRING HANDLING FUNCTIONS:C library supports a large number of string-handling functions that canbe used to carry out many of string manipulations like concatenation ,


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comparison , copy , finding length of the given string etc.

Functions

Description

srlen ( ) Determines length of a stringsrcpy ( ) Copies a string from source to destinationsrncpy()

Copies character of a string to another string upto thespecified length.

srcmp( )

Compares characters of two strings

sricmp()

Compares two strings

srncmp()

Compares characters of two strings upto specified length

srnicmp

( )

Compares characters of two strings upto specified length.

Ignores case.srlwr( ) Converts uppercase characters of a string to lowercasesrupr( ) Converts lower characters of a string to upper`srdup( ) Duplicates a string.strchr( ) Determines first occurrence of a given character in a stringstrrchr()

Determines last occurrence of a given character in a string

strstr ( ) Determines first occurrence of a given string in anotherstring

strcat( ) Appends source string to destination string.strncat(

)

Appends source string to destination string upto specified

length.strrev( ) Reverses all characters of a string.strset( )

Sets all characters of string with a given argument orsymbol.

strnset ()

Sets specified numbers of characters of string with a givenargument or symbol.

strspn( ) Finds upto what length two strings are identical.strpbrk()

Searches the first occurrence of the character in a givenstring and then it displays the string starting from thatcharacter.

STRCAT( ) FUNCTION:Syntax:

Example:Part1=computer ;


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Strcat(part1,science);In the given syntax string1,string2 are character arrays. When

the function is executed string2 is appended to string1 by removingnull characters at the end of string1. thus in the given example theoutput should be computer science. Thus the resultant value is

stored in part1.

STRCMP( ) FUNCTION:Syntax:

Example:Part1=computer ;Strcmp(part1,computer );

The above function compares the two given strings string1 and string2and return value 0 if both are equal .if not it will return the numericaldifference between the mismatching characters in the strings. In theabove example it return o as a value.STRCPY( ) FUNCTION:Syntax:

Example:Strcpy(part1,science);In the given syntax string1,string2 are character arrays.

When the function is executed string2 is copied to string1. Thus in thegiven example the output should be science. Thus the resultantvalue is stored in part1.

STRLEN( ) FUNCTION:Syntax:

Example:Part1=computer;N = Strlen(part1);In the given syntax string1 is character array. When the

function is executed it counts and returns number of characters in astring. The counting ends at the first null character. Thus in the givenexample the output should be 8. Thus the resultant value is stored in


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N.

USER-DEFINED FUNCTIONS:

DEFINITION:

A function is a self-contained block of code that performs a particulartask. once a function is designed and blocked it is called as black-boxthat takes some data from the main program and returns value.

Example:Printline(){

int a;for(a=1;a


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______________abc(x,y,z); Function call

Actual argument______________

}abc(l,k,j) Function definition{

Formal argument________________

return();}

Actual argumentThe arguments of calling function are actual arguments In theabove example, x , y and z are actual arguments.Formal argumentsThe arguments of called function are formal arguments. In theabove example, l , k and j are formal arguments.Function name

Here, abc is a function name.Argument list

Variable names enclosed within parenthesis arecalled argument list.

Function callA function can be called by its name, terminated by

a semicolon.Example

function fact (int n1){

int f1;for(i =1;i


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Local and Global variablesThere are 2 kinds of variables.

Local variables The local variables are defined within the body of thefunction. The variable defined is local to that function only. Otherfunctions can not access these variables.Global variables

Global variables are defined outside the main( ) function.Multiple functions can use them.local variables: Global variables:

Can be accessed only in thefunction where it has been

declared.

Can be accessed by all thefunctions in the program.

Needs to be declared inside thefunction where it is to be used.

Needs to be declared in the globaldeclaration section outside allprograms.

Variables are secure. Can be used by many functionsand so are not secure.

Stored in separate locations , soaccessing will change the valueonly in the function where itsused.

Stored in one location, so anyfunction accessing can changeits value.

Example:int m;main( ){

int i;float balance;....function1( );

}function1( )

{int i;float sum;

}In the above example, variable m is a global variable and

can be accessed anywhere in the program where as variable i is a


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local variable and should be accessed only in the function in whichit is declared. The variables balance and sum are local variablesand can be accessed in the functions main and function1respectively.7The Return Statement

The user defined functions uses a return statement to return thevalue to the calling function. Exit from the called function to thecalling function is done by the use of a return statement. Whenthe return statement is executed it always returns 1.Eg. Write a program to use a return statement in differentways.#include#includemain( ){int pass(int);

int x,y;clrscr( );printf( enter the value of x:);scanf(%d,&x);if(x= =1|| x


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whether a value is returned or not, may belong to one of thefollowing categories.1. Functions with no arguments and no return values.2. Functions with arguments and no return values.3. Functions with arguments and return values.

4. Functions with no arguments and return values.

No Arguments and no return values:When a function has no arguments, it does not receive any datafrom the calling function. Similarly, when it does not return avalue, the calling function does not receive any data from thecalled function. So there is only a transfer of control between thecalling and the called function, but not a data transfer.

Example:/* addition of two numbers*/#include

main( ){

add ( );}

/* function definition*/add(){

int a,b;a=a+b;printf(%d,a);return(0);

}With Arguments but no return values:

In the previous category there is no data communication betweenthe functions. So this approach is not better. To make it efficientlywe could make the calling function to read data from the terminaland pass it on to the called function. The nature of datacommunication between the calling function and the calledfunction is with arguments but no return values.


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Example:

/* addition of two numbers*/#includemain( )

{int a=2,b=3;add (a,b);

}

/* function definition*/add(int a1,int b1){

a1=a1+b1;printf(%d,a1);return;

}The arguments that we are using in the main function are calledactual arguments. The arguments that we are using in thecalled function instead of the actual arguments are called asformal arguments.When a function call is made, only a copy of the values of actualarguments is passed into the called function. Changes inside thefunction will have no effect on variables used in the actual

argument list.With Arguments and return values:In the previous category the calling function sends some data tothe called function, but the called function does not returnanything to the calling function. So it is like one-waycommunication. To make it more effective, both send and receivedata in this category. If there is any change of values in calledfunction, it has to be shown in the main function also.

Example:/* addition of two numbers*/#include

main( )


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{int a,b,c;c=add (a,b);printf(%d,c);getch();

}/* function definition*/add(int a1,int b1){

a1=a1+b1;return(a1);

}With no arguments and return values:

Eg. Program without passing any value through main( )#includemain( ){int sum( ), a,s;

clrscr( );s=sum( );printf(Sum =%d, s);return 0;}sum( ){int x,y,z;printf( Enter the values);scanf(%d%d%d,&x,&,&z);return(x+y+z);

}Output:Enter three values: 3 5 4Sum = 13Call by value and ReferenceThereare 2 ways in which we can pass arguments to the function.Call by value69.Values of actual arguments are passed to the formal


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arguments and the operation is done on the formal arguments.70.Any change made in the formal argument does not affect the

actual arguments.71.Example/* swapping of two numbers*/

#includemain( ){

int a=3,b=4;swap(a, b);

printf(In main);printf(a=%d, b=%d, a, b);

getch();}/* function definition*/

swap(int a, int b)

{ int t;t=a;a=b;b=t;printf(In function swap);printf(a=%d, b=%d, a, b)

}OUTPUT

In function swapa=4, b=3

In maina=3, b=4

Call by Reference72.Instead of passing value, addresses are passed.73.Function operates on addresses rather than values.74.Any change made in the formal argument will affect the actual

arguments.Example/* swapping of two numbers*/

#includemain( )

{int a=3,b=4;swap(&a, &b);

printf(In main);printf(a=%d, b=%d, a, b);

getch();}/* function definition*/


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swap(int *a, int *b){

int t;t=*a;*a=*b;

*b=t;printf(In function swap);printf(a=%d, b=%d, a, b)

}OUTPUT

In function swapa=4, b=3In maina=4, b=3

Function Returning More values:Eg:Write a program to return more than onevalue from a

user-defined function.#include

#includemain( ){int x,y, add, sub, change(int *, int *, int *, int *);clrscr( );printf( Enter values of X and Y:));scanf(%d%d, &x, &y);change(&x,&y, &add, &sub);printf(Addition:%d, add);

printf(Subtraction: %d, sub);return 0;}change(int * a, int * b, int *c, int *d){*c=*a+*b;*d= *a-*b;}Output:Enter values of X and Y: 5 4Addition:9

Subtraction: 1

Function as an argument:Eg: Write a program to pass a user-defined function as anargument to another function:main ( ){int y=2, x;


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x= double(square(y));printf(x=%d, x);}double(m){

return(m*2);}square(k){return(k*k);}Output:x=8

Functions with Array and pointersa) Initialization of an array using a function::

Like the values of simple variables, it is also possible to passthe values of an array to a function. To pass an array to a calledfunction, it is enough to list the name of the array, without anysubscripts and the size of the array as arguments.Example:Lar(a,n);

Array size of the arrayName

/* program to find smallest element among given set of

elements*/#includemain(){

float smallest(float,int);static float a[5]={1.0 , 4.0 , 50.34 , 60.3 , 1.0};printf(%f,smallest(a,5));

}/* function definition*/float smallest (float a[], int m){

int i;float small;small=a[0];for(i=1;i


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b) Passing array elements to a function:Eg:Void main( ){int k, show(int, int);

int num[ ] ={ 12,13,14,15,16,17,18};clrscr( );for (k=0;k


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num[2] = 14num[1] = 13num[0] = 12d) Copying an array:Void main( )

{int cpy(int *, int *), h;int a1[ ] ={ 1,2,3,4,5};clrscr( );cpy(&a1[0], &a2[0]);printf(:Source Target);for (h=0;h


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static int k;int b[5]={1,2,3,4,5};return(b[k++];}Output:

1 2 3 4 5Output:1 2 3 4 5

Recursion:75.Recursion is the process where a function is called repetitively

by itself.76.The recursion can be used directly or indirectly.Direct recursionA function calls itself till the condition is true.Example 1:

//program to find the factorial of a number#includemain(){

int n;scanf(%d,&n);printf(%d,factorial(n));

}

factorial(int n){

int fact;if(n==1)

return 1;else

fact=n*factorial(n-1);return(fact);

}

Steps:1.When n=3, fact=3*factorial(2)2.When n=2, fact=2*factorial(1)

3.When n=1, 1 is returned & control goes to step 1where fact = 2*1=2 & control is returned to step 1where fact = 3*2=6 & value is given to the calling

functionIndirect RecursionA function calls another function then the called function calls thecalling function.Example.


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Void main(){

add();}add()

{ static int i=0;while (i


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Example:main(){

int a=1000;function2();

printf(%d\n,a);}function2(){

int a=10;function1();

printf(%d\n,a);}function1(){

int a=100;

printf(%d\n,a);}Output:

100101000

EXTERNAL VARIABLES:

Variables that are both alive and active throughout the program areexternal or global variables.

They can be accessed by any function within the program. They are declared outside a function. Once a variable is declared as global any function can change its

value. Therefore these are generally used when values are to beshared between functions.

A global variable is visible only from the point where it is declared.main()

{y=5;

}int y;f1(){

y=y+1;}

This will cause the compiler to generate an error message since y hasnot been defined in the function main.To avoid this we use the storage class extern.


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main(){

extern int y;

}f1(){

extern int y;

} The keyword extern informs the compiler that thevariable y has

been declared somewhere and asks to perform a lookup for thevariable. The extern declaration does not allocate storage space forthe variables.

Multiple files can share a variable provided it is declared as enexternal variable (i.e) it is declared as a global variable in one fileand specified as an extern in the other.

Example:int a;main(){

a=10;function2();printf(%d\n,a);

}

function2(){

a=a*10;function1();printf(%d\n,a);

}function1(){

a=a*10;printf(%d\n,a);

}

Output:100010001000

STATIC VARIABLES: The value of static variables persist until the end of the program.


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Can be of internal or external type depending on the place ofdeclaration.

Internal static variables are those that are declared inside afunction.They are similar to auto variables but are alive throughoutthe entire program. They are used to retain values between function

calls. External static variables are those that are declared outside

functions. A static external variable is available only within the file where it is

declared. A static variable is initialized only once.Example:/*Static variable example*/main(){

int i;

for( i = 0; i


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VISIBILITY AND LIFETIME OF VARIABLES:

Storageclass

Place of Declaration Visibility Lifetime

None Before all functionsin a file Entire file + other fileswhere variable isdeclared as extern.

EntireProgram(Glal)

Extern Before all functionsin a file

Entire file + other fileswhere variable isdeclared as extern andthe file where it isoriginally declared asglobal.

Global.

Static(external)

Before all functionsin a file Only in that file

Global

None orauto

Inside a function Only in that function Until end function

Register Inside a function Only in that function Until end function

Static(internal)

Inside a function Only in that function Global

POINTERS:A pointer is a variable that contains an address which is a

location of another variable in memory.

Advantages of using pointers:1. A pointer enables us to access a variable that is defined outsidethe function.2. Pointers are more efficient in handling the data tables.3. Pointers reduce the length and complexity of a program.4. They increase the execution speed.5. The use of a pointer array to character strings results in saving ofdata storage space in memory.

REPRESENTATION OF A VARIABLE:


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The computers memory is a sequential collection ofstoragecells called as a byte. Each byte has a unique address associatedwith it. Whenever a variable is declared the value will be stored in amemory location in the given name. Thus it may have some addressthe above quantity is a variable name with the content 100 stored in

the location 5000. If we use a pointer variable for indicating thiscontent then the pointer variable itself contains the address 5000 as itsvalue. Thus pointer variable is a variable which contains the address ofanother variable. Using pointer variable p the memory representationwill be as like as follows

Accessing a variable using pointers: The address of a variable can be accessed by using the

symbol & which is called as address of the variable. In our scanffunction we use this operator to indicate the address of a variable.Thus to assign the address of a variable to the pointer variable we canuse this operator.Example:

p = &quantity;Thus in the above example p is a pointer variable which holds the

address of the variable quantity.

DECLARING AND INITIALIZING POINTERS:In C , every variable must be declared for its type. Since

pointer variables contain the address of a variable , they must bedeclared before we use them. The declaration of pointer variable takesthe followingformSyntax:

The above tells the compiler three things about the variable pt_name.1. The asterisk (*) tells that the variable pt_name is a pointervariable.2. pt_name needs a memory location.3. pt_name points to a variable of type data type.Example:

int *p;


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declares the variable p as a pointer variable that points to an integerdata type. The type int refers to the data type of the variable beingpointed to by p and not the type of the value of the pointer. Similarlythe statement

float * x;

declares x as a pointer to a floating point variable. Once a pointer hasbeen declared , it can be made to point to a variable using anassignment statement such as

p = &quantity;Thus p now contains the address of the variable quantity. This ascalledpointer initialization.

ACCESSING VALUE OF A VARIABLE THROUGH POINTERS:Once a pointer has been assigned the address of a variable ,

we can access the content using the indirection operator (*).Example:

int quantity, *p, n;quantity = 100;p = &quantity;n = *p;

Statements Quantity pn

5000 5010 5020

int quantity, *p, n;

quantity = 100;

p = &quantity;

n = *p;

Thus in the above example the first statement declares the pointervariable p ,which points to integer data type. In the second statement100 is assigned to quantity. In the third statement the address isassigned to the pointer variable p. In the fourth statement the contentis assigned to the variable n.

POINTER EXPRESSIONS:Like other variables, pointer variables can be used in

expressions. For example , if p1 and p2 are properly declared andinitialized pointers, then the following statements are true.

y = *p1 * *p2;sum =sum+ *p;p1++;


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requires two bytes, the first element will be stored as follows.

elements x[0] x[1] x[2] x[3] x[4]valueaddress 1000 1002 1004 1006 1008

base addressThe name x is defined as a constant pointer pointing to the first

element ,x[0] and therefore the value of x is 1000,the location wherex[0]is stored. That is

x = &x[0] = 1000If we declare p as a pointer , then we can make the pointer p to thearray x by the following assignment:

p=x;That is equivalent to

p=&x[0];

Suppose if we want to access the next element then we canincrement the address by p++ to move from one element to another.The relationship between p and x is shown below:

P= &x[0] (=1000)P+1=&x[1] (=1002)

P+2=&x[2] (=1004)P+3=&x[3] (=1006)P+4=&x[4] (=1008)

The formula for calculating the effective address of ith element if

Example:/*Program to calculate the sum of numbers in an array using

pointers*/#includeMain()

{int x[10], *p, i, sum=0;printf(Enter the elements\n);for(i=0;i


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}printf(Sum = %d,sum);

}

Pointers to two dimensional array:

0 1 2

(1,1)

(2,0)(3,0)

(3,2)

p pointer to the first row

p+i pointer to the ith row*(p+i) pointer to first element in the ith

row*(p+i)+j pointer to jth element in the ith

row*(*(p+i)+j) value stored in the cell(i,j)

Example:/*Program to find the transpose of a matrix*/

#include

main()

{

int a[5][3],i,j;

printf(Enter the values of the 5*3 matrix\n);

for(i=0;i


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scanf(%d,&a[i][j]);

}

}

printf(Original Matrix\n);

for(i=0;i


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}

getch();

}

POINTERS AND CHARACTER STRINGS:A string is an array of characters , terminated with null

character. Like in one dimensional arrays, we can use a pointer toaccess the individual characters in a string.Example:

#includeMain( ){

char*name;int length;char *cptr =name;name=delhi;while (*cptr!=\0){

printf(%c is stored at address %u,*cptr,cptr);cptr++;

}length=cptr-name;printf(length %d,length);

}Thus the above program finds the length of the given string.Pointers can also be used to handle tables of strings.Example: Static char *name[3]={Delhi,Bombay,Chennai}Declares name to be an array of three pointers to characters as shownbelow

Name[0]-delhiName[1]-Bombay

Name[2]-Chennai*(name[I]+j) is used to access the jth character in the ith row .

Thus *p[3] denotes p as an array of three pointers.(*p)[3] denotes p as a pointer to an array of three elements.

POINTERS AND FUNCTIONS:The address of a variable can be passed on to a function. When

we the address to a function the parameters should be declared as


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pointers of the appropriate datatype.The process of calling a function

using pointers to pass the address of a variable is known as call by

reference. The function that can be called by reference van change the

value of the variable used in the call.

Example:

#include

Main(){

int x=100,y=200;

printf(Before exchange : x = %d y = %d\n,x,y);exchange(&x,&y);printf(After exchange : x = %d y = %d\n,x,y);

}exchange(int *a, *b){

int t;t=*a;*a = *b;*b = t;

}

Output:Before exchange : x=100 y=200

After exchange : x=200 y=100Thus, call by reference provides a mechanism by which the functioncan change the stored values in the calling function.Note:

The function parameters are declared as pointers and are used inthe function body.

When a function is called, the addresses are passed as actualparameters.

Pointers to functions:A function also has an address in the memory. So it is possible to

declare a pointer to a function.

Syntax:


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Example:

/*Program to calculate 2*x*x*/

#include

void Main()

{

int exp(),val(),I,v;

for(I=1;I


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{

return(I*I);

}

ARRAY OF POINTERS:

Similar to an array of integers or an array of characters, we can

have an array of pointers. Since a pointer variable contains the address

of an another variable, an array of pointers contains a collection of

addresses. The addresses of array elements can be the addresses of

isolated variables or the addresses of other array elements.

Example:

/*Array of pointers to isolated variable*/

#include

main()

{

int *arr[3],i=10,j=20,k=30,m;

arr[0]=&I;

arr[1]=&j;


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arr[2]=&k;

for(m=0;m


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7000 7002 7004

A multidimensional array can be expressed in terms of array of

pointers. Thus a two dimensional array can be declared as a series of

one dimensional arrays as follows.

Datatype *array[expression1];

In general a n-dimensional array can be declared as follows

Syntax:

Example:

/*Array of pointers to one dimensional arrays*/

#include

void main()

{

int *p[3],I,j;

int a[]={1,2,3},b[]={4,5,6},c[]={7,8,9};

p[0]=a;

p[1]=b;

p[2]=c;


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printf(the values are\n);

for(I=0;I


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Preprocessor Directives :

Introduction of Preprocessor Directives:The steps for execution of any program:

77.C program is written in the editor.

78.Compilation79.Linking80.The executable code is generated. In between these stages there also involves one stage i.ePreprocessor. One of the most important features of C language isto offer preprocessor directives. The preprocessor is a program that processes the sourceprogram before it is passed on to the compiler. The program typed in the editor is the source code to thepreprocessor. The preprocessor then passes the source code tothe compiler.

The preprocessor is a program that processes the sourcecode before it passes through the compiler.81.It operates under the preprocessor directives or preprocessor

command lines. Preprocessor directives are placed before themain() function.

Rules:

Preprocessor directives begin with #. They are placed before the main() function. They do not require a semicolon at the end.

The #define DirectiveThe syntax of #define directive is as follows:#define identifier

OR#define identifier (argument 1.. argument N)

substitute textExample:

# define PI 3.14 This statement defines macro templates. During

preprocessing the preprocessor replaces every occurrence of PIwith 3.14 . Here PI is the Macro template and 3.14 is its macro

expansion. The macro templates are generally declared in capitalletters.The macro definition can be terminated with semi-colon and it isoptional. The words followed by # are not keywords and theprogrammer can use these words for variable names.Program:

#include#define M 5


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#define AND &define EQUALS ==void main(){

int a=5;

printf(Value = %d,M*5);}Output:Value = 25Program:

#include#define CUBE(x) x*x*xvoid main(){

int a,res;printf(Enter value);

scanf(%d,&a);res=CUBE(a);printf(Result = %d\n,res);

}Example:Write a program to define macros for logical operators.

#include#include# define equal = =# define larger >void main ()

{int a,b,c;clrscr();printf(Enter three Numbers:);scanf(%d %d %d ,&a,&b,&c);if (a larger b and a larger c)

printf(%d is the larger number ,a);elseif(b larger a and b larger c)

printf(%d is the larger number,b);else

if(c larger a and c larger b)printf(%d is the larger number,c);elseif(a equals b and b equal c)printf(\n Numbers are same);

}Output:Enter three numbers: 5 4 8


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8 is the larger numberUndefining a macro:

A defined macro can be undefined, using the statement#undef identifer

Example:

Write a program to undefined a macro.#include#include#define wait getche()void main(){

int k;# undef wait getche();clrscr();for(k=1;k


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Write a program to find the larger of the two numbers usingmacro with arguments.

#include#include# define MAX(x,y) if (x>y) c=x; else c=y;

void main(){int x=5,y=8,c;clrscr();MAX(x,y);printf(\n Larger of two numbers = %d,c);

}Output:Larger of two numbers = 8Explanation:

In the above program macro MAX() is defined with two

arguments x and y. When a macro is called, its correspondingexpression is executed and result is displayed .The expressioncontains if statement that determines the largest number andassigns it to variable c.

The # include Directive The # include directive loads specified file in the

current program. The macros and functions of loaded file can becalled in the current program. The included file is also compiledwith current program.The syntax is

# include file nameor #include where # is a symbol used with directives.1) The filename is included in the double quotation marks whichindicates that the search for the file is made in the currentdirectory and in the standard directories .Example:Write a program to call the function defined in udf.c file

#include#include# include udf.cvoid main()

{clrscr();display();

}Output:Function calledContents of udf.c fileint display();


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display(){

printf(\n Function called);return0;

}

Explanation:In the first program the udf.c is included .It is a user-defined function file .It is compiled before the main program iscompiled. The complete programs along with the included one areexecuted. The output of the program Function called isdisplayed.Conditional Compilation

The most frequently used conditional directives are:82.#if83.#else84.#endif etc.

These directives allow programmer to include the portions of thecodes based on the conditions. The compiler compiles selectedportion of the source codes based on the conditions.Syntax of #ifdef#ifdef{

statement1;statement2;

}#else{

statement3;statement4;

}#endif

The #ifdef preprocessor tests whether the identifier hasdefined substitute text or not. If the identifier is defined then #ifblock is compiled and executed. The compiler ignores #else blockeven if errors are intentionally made. Error messages will not bedisplayed . if identifier is not defined then #else block is compiledand executed.Example:

Write a program with conditional compilation as to whether theidentifier is defined or not.

#include#include#define E =void main(){

int a,b,c,d;


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clrscr();#ifdef E{

a E2;b E 3;

printf(A=%d &B=%d,a,b);}#else{

c=2;d=3;printf(C=%d & D=%d,c,d);

}#endifgetche();}

Output:A=2 &B=3Explanation:

The compiler search for the identifier E . The compilersearches for the identifier E. If it is found then execution of #ifblock takes place otherwise #else block. The #endif statementindicates the end of #if-#endif block.

The #ifndef DirectiveThe syntax of #ifndef directive is given below

#ifndef

{statement 1;statement 2;

}#else{

statement 3;statement 4;

}#endif

The #ifndef works exactly opposite to that of #ifdef. The #ifndef

preprocessor tests whether the identifier has defined substitutetext or not. If the identifier is defined then #else block is compiledand executed and the compiler ignores #If block even if errorsare intentionally made. Error messages will not be displayed. Ifidentifier is not defined then #if block is compiled and executed.Example:Write a program to check conditional compilation directives using#ifndef .


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#include#include#define T 8void main(){

clrscr();#ifndef Tprintf(\n Macro is defined ,);#elseprintf(\n Macro is defined);#endif

}OutputMacro is defined.Explanation:

In the above program #ifndef checks for the identifier

T. If it is defined the #else block is executed. On execution of theblock the output of the program is Macro is defined. In case theidentifier is undefined the #else block is executed and output isMacro is not defined.The #error directive

The # error is used to display user defined messageduring compilation of the program. The syntax is# if !defined (identifier)# error # endifExample:

Write a program to display user-defined error message using#error directive.

#include#include#define B 1void main(){

clrscr();#if !defined(A)#error MACRO A IS NOT DEFINED#else

printf(Macro found);#endif

}Explanation:

In the above program identifier B is defined. In theabsence of identifier an error is generated and the #errordirective displays the error message. The error message is userdefined and displayed in the message box at the bottom of the


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editor. The # defined directrive will work opposite to the #!defineddirective. The syntax is

# if defined{

}#else# error # endif

The #line directiveThe syntax is

#line []This causes the compiler to imagine the line number of

the next source line is given by and gives the current input file. If is absent , then the

cuurent file name remains unchanged.Example : # line 15 add.cThe INLINE directive

Reports the compiler that the source code has in lineasm statements. The source code will contain the assemblycode.The #pragma SAVEREGS

It guarantees that a huge function will not modify thevalue of any of the registers when it is entered. Place thisdirective immediately preceding the function definition.The #pragma DIRECTIVE

The ANSI-C and TURBO-C provide pragma directives >these # pragma directives are defined with #(hash) and these arethe preprocessor directives. It sets/resets certain warning anderrors during compilation of C program.Syntax:

# pragma warn +xxx# pragma warn xxx

ANSI Violations and #pragma

# pragma name Warning On Warning off

Hexadecimal oroctal constant toolarge

+big -big

Redefinition notidentical

+dup -dup

Both return andreturn of a valueused

+ret -ret


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Not part of structure

+str -str

Undefinedstructure

+stu -stu

Suspicious pointer

conversion

+sus -sus

Void functionscannot return avalue

+voi -voi

Zero lengthstructure

+zst -zst

Common errors and #pragma#pragma name Warning On Warning

offAssigned a value but neverused

+aus -aus

Possible use before definition +def -def Code has no effect +eff -eff Parameter never used +par -parPossibly incorrect assignment +pia -piaUnreachable code +rch -rchFunction should return avalue

+rvl -rvl

Ambiguous operators needparenthesis

+amb -amb

Less Common Errors and #pragma#pragma name Warning On Warning Off

Superfluous &with function orarray

+amp -amp

No declarationfor function

+nod -nod

Call to functionwith noprototype

+pro -pro

Structure passedby value

+stu -stu

Declared but

never used

+use -use

Portability Warnings and #pragma#Pragma name Warning On Warning Off Nonportablepointerassignment

+apt -apt

Constant is long +cln -cln


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Non-portablepointercomparison

+cpt -cpt

Constant out ofrange in

comparison

+rng -rng

Non-portablepointerconversion

+rpt -rpt

Conversion canlose significantdigits

+sig -sig

Mixing pointersto signed andunsigned char

+ucp -ucp

Example:Write a program to set off certain errors shown by the programusing #pragma directive

#include#include#pragma warn-aus#pragma warn-def#pragma warn-rvl#pragma warn-usemain (){

int x=2,y,z;printf (\n y=%d,y);

}

Explanation:The above program contains following warnings

85.Possible use of y before definition in function.86.Z is declared but never used in function main.87.x is assigned a value which is never used in function.88.Function should return a value in function main.The display of these errors can be made on/off by using

the pragma options.Standard i/o predefined Streams in Stdio.h

The predefined streams automatically opens when the programis started.

Standard i/o predefined macros in stdio.hMacros Function Definition in stdio.h


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Stdin Standard input device #define stdin(&streams[0])

Stdout Standard outputdevice

#define stdout(&streams[1])

Stderr Standard error output

device

#define stderr

(&streams[2])Stdaux Standard auxiliarydevice

#define stdaux(&streams[3])

Stdprn Standard printer #define stdprn(&streams[4])

Example:Write a program to enter text and display it using macroexpansions.

#include#includevoid main()

{char ch[12];int i;clrscr();printf(input a text:);for(i=0;i


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ispunct(d) d is a punctuationIsprint(d) d is a printable characterisgraph(d) d is a printable but not a spaceiscntrl(d) d is a control characterisascii(d) d is an ascii code

DYNAMIC MEMORY ALLOCATION:

C requires the number of elements to be specified at the compile

time. Sometimes our initial judgement of the size of the arrays may be

wrong (i.e) space may be wasted or more space will be required . To

avoid such problems C allows the user to specify the size of the array

at run time. This is called dynamic memory management. Thus the

process of allocating memory at run time is known as dynamic memory

allocation.C uses four library functions to support dynamic memory

allocation. They are

Malloc allocates requested size of bytes and returns a pointer tothe first byte of the allocated space.

Calloc allocates space for an array, initializes them to zero andthen returns a pointer to the memory.

Free frees previously allocated memory. Realloc modifies the size of the previously allocated array.

Storage of a C program

Stack

Heap


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Permanent storage area

The global variables and the instructions are stored in the

permanent storage area. Local variables are stored in the stack. The

free region is called the heap and is used for dynamic memory

allocation. The heap keeps changing when the program is executed

when the variables are created and destroyed. Therefore memory

overflows can occur. In that case the memory allocation processes

returns a NULL pointer to denote a failure to allocate the requested

memory space.

Malloc():

A block of mamory can be allocated using malloc() function. This

allocates a block of the specified size and returns a void pointer.

Syntax:

Example:

X=(int *)malloc(100 * sizeof(int));

This statement allocates a memory space equivalent to 100 times the


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size of an int and returns the address of the first byte to the pointer x.

If the function cannot allocate memory it returns a NULL pointer.

Calloc():

Calloc() allocates multiple blocks of storage each of the same

size and initializes them to 0.

Syntax:

Example:

..

..

struct student

{

char name[25];

float age;

long int id;

};

typedef struct student record;

record *st_ptr;


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int class=30;

..

..

st_ptr=(record*)calloc(class,sizeof(record));

Free():

With dynamic allocation, the user has to release the memory

when it is not used. This is important when the storage space is

limited. The function Free() releases the memory.

Syntax:

Example:

Free(p);

Realloc():

There are 2 cases when we require to realter the memory

already allocated

1. When the previously allocated memory is not sufficient and the userrequires additional space.2. When the memory allocated is larger and the user wishes to reduceit.In both the cases the memory size can be changed with the use of


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realloc().

Syntax:

This function allocates a new memory space of size new-size to

the pointer variable ptr and returns a pointer to the first byte of the

new memory block if the memory allocation operation is successful.

The newsize may be smaller or larger than the original size. The

realloc() function does not modify the original contents. If the function

fails in allocating the required space, then it returns a NULL pointer

and the origunal block is lost.

Program:

/*Program to access a 2 dimensional array using malloc()*/

void main()

{

int *p[3], I, j,c;

printf(Enter the no of cols\n,&c);

p[0]=(int*)malloc(c*sizeof(int));

p[1]=(int*)malloc(c*sizeof(int)); allocates space for c

cols


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p[2]=(int*)malloc(c*sizeof(int));

for(I=0;I


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How they are treated?91.Can the names of formal parameters coincide with actual

parameters?92.Can multiple return statements be included in a function?93.What is a null statement? Explain its usefulness.

94.Write the syntax of goto statement.95.Write the purpose of break and continue statement.96.Explain and give example for predefined functions.97.Write the disadvantages of using goto statement.98.Write the advantages of using user defined functions.99.In what way ,a switch statement differ from an if statement?100.Say true or false:

when if statements are nested, the last else getsassociated with the nearest if without an else.

One if can have more than one else clause. A switch statement can always be replaced by a series

of if..else statements. A switch expression can be of any type A program stops its execution when a break statement

is encountered.101.How the end of the string is recognized?102.Explain the need for array variables.103.Declaration int a[10][10] creates how many elements.104.What is the value returned by a strcmp() function?105.Define array.106.Identify errors,if any, in each of the following array declaration

statements. Float values [10,13] Char name[ROW],[COLUMN];

107.Identify errors ,if any ,in each of the following initializationstatements.

Static int number[ ]={0,0,0,0,} Static char word[ ]={a,rr,r,y};

108.Define string.109.Write the common operations performed on character strings.110.Write the purpose of getchar function.111.Write the purpose of putchar function.

112.Write the function to convert the given string to integer .113.Which function is used to convert the given integer value tostring?

114.Write any four string handling functions.115.Describe the limitations of using getchar and scanf functions for

reading strings.116.What is recursive function?117.What happens when actual arguments are less than formal


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arguments in a function?118.What happens when data type of one of the actual arguments

does not match with the type of the function.119.What happens when same variable is used in two different

functions?

120.Say true or false Function should be arranged in the order in which they

are called. We can pass any number of arguments to a function. A function in c should have atleast one argument.

121.What are the different storage classes?

Section B

122.Write short notes on functions123.Differentiate local and global variables124.Write short notes on different types of arguments

125.Explain string handling functions in detail with examples.126.Write a program which will read a text and count all

occurrences of a particular word.127.Explain the usage of break & continue statement128.Write short notes on conditional operatorWrite short notes

on multidimensional arrays129.Write a program to search an element using linear search.130.Write a program to sort the given set elements using

selection sort131.Write a program to arrange the given set of element using

ascending order.

132.Write a program to arrange the given set numbers indescending order.

133.Write a program to add two given matrices of order m x n134.Explain about switch statement135.Distinguish between local and global variables136.Distinguish between formal and actual arguments.137.Distinguish between automatic and static variables.138.Distinguish between global and extern variables.139.Is the main user defined function? If yes means how it differs

from the other user defined functions?140.Write a program to calculate npr using user defined function.

141.Write a recursive program to generate fibonacci nubers142.Write shorts notes on auto storage class143.Explain about register & extern variables144.Write a recursive program to calculate the factorial of a

given number.145.Write a program to find if a string is a palindrome or not.

Section C


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146.Explain recursion with an example147.Explain about user defined functions148.Write a program to sort a set of numbers and to print

minimum & maximumof the set

149.Explain multidimentional arrays.150.Write a program to find sum of positive & negative realnumbers seperatelyfrom a given set of real numbers using continue and while

statement151.Explain any 4 string functions with examples152.Discuss on different storage classes

8. Write a program to print the set of names in alphabeticalorder

9. Write a program

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