Basic of C Program

8/12/2019 Basic of C Program

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BASICS OF CPROGRAMMING

By Prof. Ahlam S. A. Ansari


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Structure of a C Program

Documentation

Header Files

Symbolic Constants

Global & Constant Variable Declaration

Main Function

Other Functions

By- Prof. Ahlam Ansari2


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Structure of Main function

void main()

{ Initialization Statements clrscr(); Input Statements Processing Statements

Output Statements getch();

}



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Fundamentals of C Programming

CharacterSet

Constants,Variables

&Keywords

Instructions Programs



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Character Set

Alphabets :Uppercase: A B C .................................... X Y ZLowercase: a b c ...................................... x y zDigits :0 1 2 3 4 5 6 8 9Special Characters :


, < > . _ ( ) ; $ : % [ ] # ?' & { } " ^ ! * / | - \ ~ +


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CharacterSet

Constants,Variables

&Keywords




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Token

Token

Keyword Constant Identifier String Operator


The smallest individual unit in a program isknown as a TOKEN.


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Keywords

auto double int struct

break else long switch

case enum register typedef

char extern return union

continue for signed void

do if static whiledefault goto sizeof volatile

const float short unsigned


Keywords are the reserved words used in programming. Each keywords has fixedmeaning and that cannot be changed by user.


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Identifiers

In C programming, identifiers are names given to Centities, such as variables, functions, structures etc.Identifier are created to give unique name to C

entities to identify it during the execution of program.


Example:int sum;

Here sum is an IDENTIFIER

Example:struct student

Here student is a IDENTIFIER

Example: void add()Here add is a IDENTIFIER


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Rules for writing identifier

1. An identifier can be composed of letters, digits andunderscore '_' only.

2. Uppercase and lowercase letters are distinct.3. The first letter of identifier should be either a letter

or an underscore. But, it is discouraged to start anidentifier name with an underscore though it islegal.

4. There is no rule for the length of an identifier.



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Constant

Constant

Numeric

Integer

Ex. Whole No (15, -90)

Real

Ex. Decimal No (-12.33,34.44)

Backslash

Ex.\n,\t,\a,\v,\b,\f,\\,\

Symbolic

Ex. #define PI 3.14 ,#define A 3*3

Character

Single Character

Ex. h, 6, @

String

Ex. C- Program


Constants are the terms that can't be changed during theexecution of a program.


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Defining Constant

Method 1:const float pi=3.14;

#include

void main(){

const float pi=3.14;

.

.

.

}



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Continued...

Method 2:#define pi 3.14

#include

#define pi 3.14void main()

{

.

.

.

}



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Backslash Constant

\n New Line Character#includevoid main(){

printf("Hello\n Class");}


Output:

HelloClass_


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Backslash Constant

\t Tab Character#includevoid main(){

printf("Hello\t Class");}


Output:

Hello Class_


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Backslash Constant

\b BackspaceCharacter

#includevoid main(){

printf("Hello\b");}


Output:

Hell_


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Backslash Constant

\a Alert Character#includevoid main(){

printf("Hello\a");}


Output:

Hello_Note: After output a

System sound beep isheard.


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Backslash Constant

\r Return CarriageCharacter


printf("Hello\r");}


Output:

_ello


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Backslash Constant

\f Form FeedCharacter


printf("Hello\n Class\f");}


Output:

_elloClass


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Backslash Constant

\\ , \ and \ Character#includevoid main(){

printf(\\ \ \");}


Output:

\ _


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Variable

Variables are memory location in computer'smemory to store data. To indicate the memorylocation, each variable should be given a unique

name called identifier. Variable names are just thesymbolic representation of a memory location.


Example:int num;

Here num is a VARIABLE


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Rules for writing Variable

1. Variable can be composed of letters, digits andunderscore '_' only.

2. Uppercase and lowercase letters are distinct.3. The first letter of variable should be either a letter

or an underscore. But, it is discouraged to start anidentifier name with an underscore though it is

legal.4. There is no rule for the length of an variable.



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Scope of a VariableBy- Prof. Ahlam Ansari23

Global VariablesThese variables aredeclared outside allfunctions.

Life time of a globalvariable is the entireexecution period of the

program.

Can be accessed by any

function defined below thedeclaration, in a file.

/* Compute Area and Perimeter of acircle */

#include float pi = 3.14159; /* Global */

main() {

float rad; /* Local */

printf( Enter the radius );scanf(%f , &rad);

if ( rad > 0.0 ) {float area = pi * rad * rad;float peri = 2 * pi * rad;

printf( Area = %f\n , area ); printf( Peri = %f\n , peri );

}else

printf( Negative radius\n);

printf( Area = %f\n , area );}


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Continued....By- Prof. Ahlam Ansari24

Local VariablesThese variables aredeclared inside somefunctions.

Life time of a localvariable is the entireexecution period of thefunction in which it isdefined.

Cannot be accessed by any

other function.In general variablesdeclared inside a blockare accessible only inthat block.

/* Compute Area and Perimeter of acircle */

#include float pi = 3.14159; /* Global */

main() {float rad, area, peri; /* Local */

printf( Enter the radius );scanf(%f , &rad);

if ( rad > 0.0 ) {area = pi * rad * rad;

peri = 2 * pi * rad;

printf( Area = %f\n , area ); printf( Peri = %f\n , peri );

}else

printf( Negative radius\n);

printf( Area = %f\n , area );}


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Tips for Good Programming PracticeBy- Prof. Ahlam Ansari25

2. Programmer must write the program with proper indentation.

1. Programmer can choose the name of identifier whatever theywant. However, if the programmer choose meaningful name for anidentifier, it will be easy to understand and work on, particularly in

case of large program.


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Exercise- Find out the different tokens

/*Program to calculate area of circle*///Developed By: Ahlam Ansari#include#includevoid main(){

float radius=2.2, area;const float pi=3.14;clrscr();area=pi*radius*radius;printf(\n The area of circle with radius %fcm is %fcm.sq ,radius, area);getch();

}



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Exercise- Find out the different tokens

/*Program calculate area of triangle*///Developed By: Ahlam Ansari#include#include#define half 0.5void main(){

int base=2, height=4;float area;clrscr();area=half*base*height;printf(The area of triangle is %fcm.sq , area);getch();

}



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CharacterSet

Constants,Variables

&Keywords




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Instruction/ Statement

Instruction/Statement

TypeDeclaration

Statement

Input- OutputStatement

OperationStatement

ControlStatement



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TypeDeclaration

Statement


OperationStatement

ControlStatement



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Type Declaration Statement

Data Type

In- Built/ Basic/Primitive Data

Type

Ex. Int, float, char,long, double,

void, long double

Derived DataType

Ex. Array,Function, Pointer

User DefinedData Type

Ex. Structure,Union,

Enumeration



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Syntax:datatype identifier1[,identifiers2,...,identifiern];

Example:int a,b,c;float x;char ch=C;



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More Examples:int sum=10;float radius=20.1;

char ch=A;int add();void display();

struct student {..};long ar[50];int *ptr;



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Type Format Specifier Memory Allocation Typical Range

Bytes Bits

char %c 1byte 8 bits -127 to 127 or 0 to 255

unsigned char %c 1byte 8 bits 0 to 255

signed char %c 1byte 8 bits -127 to 127

int %d or %i 2 bytes 16 bits -2147483648 to 2147483647unsigned int %u 2 bytes 16 bits 0 to 4294967295

signed int %d or %i 2 bytes 16 bits -2147483648 to 2147483647

short int %hd 2 bytes 16 bits -32768 to 32767

unsigned short int %u 2 bytes 16 bits 0 to 65,535

signed short int %hd 2 bytes 16 bits -32768 to 32767

long int %ld 4 bytes 32 bits -2,147,483,647 to 2,147,483,647

signed long int %ld 4 bytes 32 bits same as long int

unsigned long int %u 4 bytes 32 bits 0 to 4,294,967,295

float %f 4 bytes 32 bits +/- 3.4e +/- 38 (~7 digits)

double %lf 8 bytes 64 bits +/- 1.7e +/- 308 (~15 digits)

long double %Lf 10 bytes 80 bits +/- 1.7e +/- 308 (~15 digits)



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Tips to calculate range

Example:1. Unsigned char -> 8bitsMinimum Range 0Maximum Range 28 1 => 256-1=> 255

2. Signed char -> 8bits

Minimum Range -(28 /2 ) => -(256/2) => -128Maximum Range (28 /2) 1 => 128-1=> 127


f


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Exercise Find the size of thedatatypes#include void main(){

int a; float b; double c; char d;printf("Size of int=%d bytes\n",sizeof(a));printf("Size of float=%d bytes\n",sizeof(b));printf("Size of double=%d bytes\n",sizeof(c));printf("Size of char=%d byte\n",sizeof(d));

}



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More Format Specifier

%o The unsigned octal format specifier.%s The string format specifier.%x The unsigned hexadecimal formatspecifier.%% Outputs a percent sign.



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The operands of a binary operator must have a the same type and theresult is also of the same type.Integer division:

c = (9 / 5)*(f - 32)

The operands of the division are both int and hence the result also wouldbe int. For correct results, one may writec = (9.0 / 5.0)*(f - 32)

In case the two operands of a binary operator are different, butcompatible, then they are converted to the same type by the compiler.The mechanism (set of rules) is called Automatic Type Casting.

c = (9.0 / 5)*(f - 32)

It is possible to force a conversion of an operand. This is called ExplicitType casting .c = ((float) 9 / 5)*(f - 32)


Data-Type Conversion


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char


char can be converted to short int.

Note

sizeof (char) sizeof (short int)


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long int

int

shortint


AutomaticData-TypePromotion

sizeof (short) sizeof (int) sizeof (long)

Lower data types are converted to the higher data types and result is of higher type.

Note


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long double

double

float


AutomaticData-TypePromotion

Lower data types are converted to the higher data types and result is of higher type.

Note

sizeof (float) sizeof (double) sizeof (long double)

E i Wh t i th lt t


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Exercise What is the resultantdata-type

float f; double d; long l;int i; short s;

1. d + f f will be converted to doubl e

2. i / s s will be converted to i nt3. l / i i is converted to l ong ; l ong result


It i g ll g d ti


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Type CastingBy- Prof. Ahlam Ansari43

long double

double

float

long int

intshort

int

char

The general form of a type casting operator is (type-name) expression.It is used to convert cross data-types.

It is generally a good practiceto use explicit casts than to relyon automatic type conversions.


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Syntax & Example

Syntax:

(Data-Type)Variable_name/Expression

Example:C = (float)9 / 5 * ( f 32 )

X = (long) (9.0 * 5 / 2)


1. f l oat to i nt conversion causes truncation of fractional part2. doubl e to f l oat conversion causes rounding of digits3. l ong i nt to i nt causes dropping of the higher order bits.

Note


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Exercise Find the output

#include void main(){

int i = 17;char c = 'c'; /* ascii value is 99 */float sum;

sum = (float)(i + (int)c);printf("Value of sum : %f\n", sum );

}

Output: Value of sum : 116.000000



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TypeDeclarationStatement


OperationStatement

ControlStatement



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Input Output Statement

1. scanf() and printf()include void main()

{int num;printf("Enter the number : ");

scanf(%d, &num);printf("You entered: %d", num);}



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2. getchar() and putchar()include void main()

{char ch;printf("Enter a character : ");

ch=getchar(stdin);putchar(ch,stdout);}



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3. getc() and putc()include void main()

{char ch;printf("Enter a character : ");

ch=getc ();putc(ch);}



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4. gets() and puts()include void main()

{char str[50];printf("Enter a string : ");

gets(str);puts(str);}



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5. getch() and putch()include void main()

{ char ch;printf("Enter a character : ");ch=getch();putch(ch);

}



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6. getche()include void main()

{ char ch;printf("Enter a character : ");c=getche();putch(ch);

}


Difference between getc() getch()


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Difference between getc(), getch(),getche() and getchar()

getc(): Reads a character only after Enter key ispressed.getch(): Reads a character and never waits for Enterkey. Character gets processed after getting any keypressed.getche(): It works same as getch() but it echoes onscreen.getchar(): It works differently from the other two.Whenever you press any key these are kept in Buffer.After hitting enter the first character gets processedand it echoes on the screen.



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TypeDeclarationStatement


OperationStatement

ControlStatement



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Example of Arithmetic Operator

#include void main()

{

int a=9,b=4,c;

c=a+b;

printf("a+b=%d\n",c);

c=a-b;

printf("a-b=%d\n",c);

c=a*b;

printf("a*b=%d\n",c);c=a/b;

printf("a/b=%d\n",c);

c=a%b;

printf("Remainder when a divided by b=%d\n",c);

}



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Example of Assignment Operator


int a=9,b=4,c;printf(A=%d and B= %d\n",a,b);c=a;a=b;b=c;printf(A=%d and B= %d\n",a,b);

}


Example of Short Hand Assignment


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Example of Short Hand AssignmentOperator

Operator Example Same as

= a=b a=b

+= a+=b a=a+b

-= a-=b a=a-b*= a*=b a=a*b

/= a/=b a=a/b

%= a%=b a=a%b



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Example of Logical Operator

Operator Meaning of Operator Example

&& Logial AND If c=5 and d=2 then,((c==5) && (d>5)) returns false.

|| Logical ORIf c=5 and d=2 then,(c==5) || (d>5)) returns true.

! Logical NOT If c=5 then,!(c==5) returns false.



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Example of Unary Operator


int a=-9,b=4;printf(A=%d and B= %d\n",a,b);a=-a;b=-b;printf(A=%d and B= %d\n",a,b);

}



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Example of Relational Operator

Operator Meaning of Operator Example

== Equal to 5==3 returnsfalse (0)

> Greater than 5>3 returns true(1)

< Less than 5=Greater than orequal to

5>=3 returns true(1)


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Example of Bitwise Operator

Operators Meaning of operators Example

& Bitwise AND 5&3 returns (1)

| Bitwise OR 5|3 returns (7)

^ Bitwise exclusive

OR5^3 returns (6)

~ Bitwise complement ~5 returns (10)

>3 return (1)



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Bitwise AND

Variable b 3 b2 b1 b0X =5 0 1 0 1

Y= 3 0 0 1 1

z = x & y 0 0 0 1


x y x & y0 0 00 1 01 0 0

1 1 1


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Bitwise OR

Variable b 3 b2 b1 b0X =5 0 1 0 1

Y= 3 0 0 1 1

z = x | y 0 1 1 1


x y x | y0 0 00 1 11 0 1

1 1 1


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Bitwise XOR

Variable b 3 b2 b1 b0X =5 0 1 0 1

Y= 3 0 0 1 1

z = x ^ y 0 1 1 0


x y x ^ y0 0 00 1 11 0 1

1 1 0


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Bitwise NOT

Variable b 3 b2 b1 b0X =5 0 1 0 1

z = ~x 1 0 1 0


x ~x0 11 0


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Bitwise LEFT SHIFTBy- Prof. Ahlam Ansari67

b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 b10

b11

b12

b13

b14

b15

Z=10 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1 0Z


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Example of ternary operator


int num;char result[5];printf("Enter a number ");scanf("%d",&num);result= (num % 2 == 0)?even:odd;printf(%d is %s,num,result);

}



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include void main(){

int num;printf("Enter integer number : ");scanf(%d, &num);num%2==0 ? printf("%d is a even number",num) :printf("%d is an odd number",num);

}


Example of Increment Decrement


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Example of Increment DecrementOperator

S no Operator type Operator Description

1 Pre increment++i Value of i is incrementedbefore assigning it to

variable i.

2 Post - incrementi++ Value of i is incrementedafter assigning it to variable

i.

3 Pre decrement i Value of i is decremented

before assigning it tovariable i.

4 Post _decrementi Value of i is decrementedafter assigning it to variable

i.


d


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Operator Precedence

Operator Description Associativity

( )[ ].

->++ --

Parentheses (function call)(see Note 1)Brackets (array subscript)Member selection via objectname

Member selection via pointer Postfix increment/decrement(see Note 2)

left-to-right

++ --+ -

! ~(type )*&

sizeof

Prefix increment/decrementUnary plus/minusLogical negation/bitwisecomplementCast (convert value totemporary value of type )Dereference

Address (of operand)Determine size in bytes onthis implementation

right-to-left


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Continued....By- Prof. Ahlam Ansari73 Operator Description Associativity

* / % Multiplication/division/modulusleft-to-right

+ - Addition/subtraction left-to-right

> Bitwise shift left, Bitwise shiftrightleft-to-right

< >=

Relational less than/less thanor equal toRelational greaterthan/greater than or equal to

left-to-right

== != Relational is equal to/is notequal toleft-to-right

& Bitwise AND left-to-right

^ Bitwise exclusive OR left-to-right

| Bitwise inclusive OR left-to-right

&& Logical AND left-to-right

| | Logical OR left-to-right

? : Ternary conditional right-to-left

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Continued....By- Prof. Ahlam Ansari74

Operator Description Associativity

=+= -=*= /=

%= &=^= |=

=

Assignment Addition/subtractionassignmentMultiplication/division

assignmentModulus/bitwise ANDassignmentBitwise exclusive/inclusiveOR assignmentBitwise shift left/rightassignment

right-to-left

, Comma (separateexpressions)left-to-right

F d l f C P i


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CharacterSet

Constants,Variables

&Keywords



S d d Lib F i


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Standard Library Functions

Library functions in C language are inbuilt functions which are grouped togetherand placed in a common place called library.

Each library function in C performs specific operation.

We can make use of these library functions to get the pre-defined output instead ofwriting our own code to get those outputs.

These library functions are created by the persons who designed and created Ccompilers.

All C standard library functions are declared in many header files which are savedas file_name.h.

Actually, function declaration, definition for macros are given in all header files.

We are including these header files in our C program using#include command to make use of the functions those are declaredin the header files.

When we include header files in our C program using #includecommand, all C code of the header files are included in C program. Then, this C

program is compiled by compiler and executed.


di h


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stdio.h

S.no Function Description

1 printf()This function is used to print the character, string,float, integer, octal and hexadecimal values onto theoutput screen

2 scanf() This function is used to read a character, string,numeric data from keyboard.

3 getc() It reads character from file

4 gets() It reads line from keyboard

5 getchar() It reads character from keyboard

6 puts() It writes line to o/p screen

7 putchar() It writes a character to screen


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conio.h


1 clrscr() This function is used to clear theoutput screen.

2 getch() It reads character from keyboard

3 getche() It reads character from keyboard andechoes to o/p screen


t i h


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string.h

S no String functions Description

1 strcat(str1, str2) Concatenates str2 at the end of str1.

2 strcpy(str1, str2) Copies str2 into str1

3 strlen(strl) gives the length of str1.

4 strcmp(str1, str2)Returns 0 if str1 is same as str2. Returns

0 if str1 >str2.

5 strchr(str1,char) Returns pointer to first occurrence of charin str1.

6 strstr(str1, str2) Returns pointer to first occurrence of str2in str1.

7 strcmpi(str1,str2)Same as strcmp() function. But, this

function negotiates case. A and a aretreated as same.


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Continued..

S no

Stringfunctions

Description

8 strdup() duplicates the string9 strlwr() converts string to lowercase10 strncat() appends a portion of string to another

11 strncpy() copies given number of characters of onestring to another

12 strrchr() last occurrence of given character in astring is found13 strrev() reverses the given string

14 strset() sets all character in a string to givencharacter15 strupr() converts string to uppercase


th h


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math.h

S no Function Description

1 floor ( ) This function returns the nearest integer which is lessthan or equal to the argument passed to this function.

2 round ( )

This function returns the nearest integer value of thefloat/double/long double argument passed to thisfunction. If decimal value is from .1 to .5 , itreturns integer value less than the argument. If decimalvalue is from .6 to .9 , it returns the integer valuegreater than the argument.

3 ceil ( )This function returns nearest integer value which isgreater than or equal to the argument passed to thisfunction.

4 sin ( ) This function is used to calculate sine value.

5 cos ( ) This function is used to calculate cosine.

6 cosh ( ) This function is used to calculate hyperbolic cosine.

7 exp ( ) This function is used to calculate the exponential e to

the xth

power.


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Continued...By- Prof. Ahlam Ansari82


8 tan ( ) This function is used to calculate tangent.

9 tanh ( ) This function is used to calculate hyperbolic tangent.

10 sinh ( ) This function is used to calculate hyperbolic sine.

11 log ( ) This function is used to calculates natural logarithm.

12 log10 ( ) This function is used to calculates base 10 logarithm.

13 sqrt ( ) This function is used to find square root of the argumentpassed to this function.

14 pow ( ) This is used to find the power of the given number.

15 trunc() This function truncates the decimal value from floatingpoint value and returns integer value.

tdlib h


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stdlib.hBy- Prof. Ahlam Ansari83


1. abs()

This function returns the absolute value of aninteger . The absolute value of a

number is always positive. Only integer values aresupported in C.2. abort() It terminates the C program

3. rand() This function returns the random integer numbers

4. delay() This function Suspends the execution of the program

for particular time

ct pe h


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ctype.hBy- Prof. Ahlam Ansari84


1 isalpha() checks whether character is alphabetic

2 isdigit() checks whether character is digit

3 isalnum() checks whether character is alphanumeric

4 isspace() checks whether character is space

5 islower() checks whether character is lower case

6 isupper() checks whether character is upper case

7 tolower() checks whether character is alphabetic & convertsto lower case

8 toupper() checks whether character is alphabetic & convertsto upper case

time h


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time.hBy- Prof. Ahlam Ansari85


1 setdate() This function used to modify the system date

2 getdate() This function is used to get the CPU time

3 clock() This function is used to get current system time

4 time() This function is used to get current system time asstructure

Assignment


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Assignment

1. Write at least THREE Programs based on the topiccovered.

2. Write notes on data-types.3. Explain Data-type Conversion.4. Write notes on operators used in C programming.5. Explain any five library functions.


Documents

Basic of C Program