C_Programming1

7/31/2019 C_Programming1

1/27

C Programming

Design By:Solutioncab.com


2/27

What is a language?

A Language is the Spoken and signedforms of communication among

Humankind. A formal language is a set of words, i.e.

finite strings of letters, symbols, or tokens.

The set from which these letters are takenis called the alphabet.

Eg. English, Hindi etc.


3/27

What is a language?

Communicating with a Human Being involvesspeaking the language that human being

understands.

Communicating with a computer involvesspeaking the language the computer andhuman being both understands,


4/27

What is C ?

C is a programming language developed atAT & Ts Bell Laboratories of USA in 1972. Itwas designed and written by a man namedDennis Ritchie. In the late seventies C beganto replace the more familiar languages of thattime like PL/I, ALGOL, etc.

C is often called a middle-level computerlanguage, because it has the features of bothhigh-level languages, such as BASIC,PASCAL etc., and low-level languages suchas assembly language.


5/27

How to learn Language? Steps Of Learning English Languages.

Alphabets Words Sentences Paragraphs

Steps Of Learning C.

AlphabetsDigits

Special Symbols

ConstantsVariablesKey words

Instructions Programs


6/27

The C Character Set

A character denotes any alphabet, digit orspecial symbol used to represent information.

Like:Alphabets: A,B,C.X,Y,Z

a,b,c,.....x, y, z

Digits: 0,1,2,3,4,5,6,7,8,9.

Special Symbols: ~!@#$%^&*()_+|-=\[{}];:?/


7/27

Constants, Variables & Keywords

Constants: A constant is an entity that does notchange. eg. 2, 3, 4, 900,8.675.

Variables: A variable is an entity that may

change. eg. X, f, Ram, Var_iable,u z

x = 40

x u zx = 20 20 40

Variable Constant

x

40 20 40

4020

Whose value is changing ?


8/27

Types of Constants

C constants can be divided into two majorcategories:

Primary Constants Integer Constant.

Real or Float Constant. Character Constant.

Secondary Constants Array.

Pointers

Structure.

Union

Enum etc.

(we will study later.)


9/27

Integer Constant.

Rules of Integer Constants An integer constant must have at least one digit.

It must not have a decimal point.

It can be either positive or negative. If no sign precedes an integer constant it is

assumed to be positive.

No commas or blanks are allowed within aninteger constant.

The allowable range for integer constants is -32768 to 32767.


10/27

Integer Constant.

Examples of Valid Integer Constant.

Example of Invalid Integer Constants.

Valid : 0, 1, 743, -67, 5478, 9999, etc

12,245

36.4

12 34

0900

illegal Character (,)

illegal Character(.)

illegal Character (Blank Space)

The first digit cannot be zero


11/27

Real or Float Constant.

Rules for Constructing Real Constants

A real constant must have at least onedigit.

It must have a decimal point.

It could be either positive or negative.

Default sign is positive. No commas or blanks are allowed within a

real constant.


12/27

Real or Float Constant

Example of valid Real or Float Constant+325.34 , 426.0 , -32.76, -48.5792

Example of in valid Real or Float Constant1

1,000.0

2E+10.2

3 .20

Must Have (.)

illegal Character (,)

Power cannot be in decimal (10.2)

Blank space Not allow


13/27

Real constants expressed in

exponential form: The mantissa part and the exponential part should be

separated by a letter e.

The mantissa part may have a positive or negative sign.

Default sign of mantissa part is positive. The exponent must have at least one digit, which must

be a positive or negative integer. Default sign is positive.

Range of real constants expressed in exponential form is

-3.4e38 to 3.4e38. Ex.: +3.2e-5

4.1e8

-0.2e+3

-3.2e-5

-53.2 e

Mantissa SeparatorExponent


14/27

Character Constants

Rules for Constructing Character Constants

A character constant is a single alphabet, asingle digit or a single special symbol enclosed

within single inverted commas. Both the inverted commas should point to the

left. For example, A is a valid characterconstant whereas A is not.

The maximum length of a character constantcan be 1 character.


15/27


16/27

Variable Constant Variable names are names given to locations inmemory. These locations can contain integer, real or

character constants.

The types of variables that it can support depend on

the types of constants that it can handle. This isbecause a particular type of variable can hold only thesame type of constant.

For example, An integer variable can hold only an integer constant.

A real variable can hold only a real constant.

A character variable can hold only a character constant.


17/27

Variable Constant

Rules of Variable declaration. Variables must be declared before use

immediately after {.

Valid characters are letters, digits and _ . First character cannot be a digit.

31 characters recognized for local variables.(more can be used, but are ignored).

Upper and lowercase letters are distinct.


18/27

Variable Declaration

int b;

double x;

unsigned int a;

char c; C is a typed language that means a variable has a

Type

Name

C standard types int, double, char, float, short, long, long double

unsigned char, unsigned short, unsigned int, unsigned long

int b;

Variable type Variable Name


19/27

Variable Constant

Example of Variable constants.

int a; /* General declaration */

int a = 10; /* Valued Declaration */

float b = 12.6; /* Valued Declaration */

float b; /* General declaration */

char c; /* General declaration */

char c = y; /* Valued Declaration */


20/27

Keywords.

In Standard C, the keywords have special significance to thecompiler and therefore can not be used as identifiers.

auto double int struct

break else long switchcase enum register typedefchar extern return unionconst float short unsignedcontinue for signed void

default goto sizeof volatiledo if static while


21/27

The Format of C

Statements are terminated with semicolons(;) Indentation is ignored by the compilerC is case sensitive - all keywords and

Standard Library functions are lowercaseStrings are placed in double quotes ()New lines are handled via\nPrograms are capable of flagging success or

error, those forgetting to do so have one orother chosen randomly!


22/27

printf and scanf

printfwrites

integer values to screen when %d is used float values to screen when %f is used

character values to screen when %c is used

scanf reads integer values from the keyboard when %d is used. float values from the keyboard when %f is used.

character values from the keyboard when %c is used.

& VERY important with scanf & not necessary with printf because current

value of parameter is used


23/27

The Basic Structure of a C Program

{

}

Global variables Declaration

/* Program documentation */

#Preprocessor directives

Global constants Declaration

main ()

Instructions & Statements


24/27

First C program.

#include // input-output libraryint main() // function main

{

printf(Hello World\n); // send string to standard output

}

Output: Hello world


25/27

First C program.

#include includes the standard I/O library which allows you to read from the

keyboard (standard in) and write to the screen (standard out)

int main()

declares the main function. Every C-program must have a functionnamed main somewhere in the code{ ... }

The symbols { and } mark the beginning and end of a block of code.

printf(Hello World\n)

Sends output to the screen. The portion in quotes ... is the formatstrings and describes how the data is formatted.


26/27

Second program.#include

void main(){

int a;float x;char c;

printf(Enter integer:);scanf(%d,&a);

printf(\nEnter float:);scanf(%f,&x);

printf(\nEnter character:);

scanf(%c,&c);printf(\nValue of a is %d, of x is %f, of c is %c\n,a,x,c);

}

standard I/O filemain function

declare a variable of type integer.declare a variable of type float.declare a variable of type character.

display on screenEnter integer.store the integer value in a.display on screenEnter Float.store the Floatvalue in x.

display on screenEnter character.

store the charactervalue in c.gives output

Code block starts/ Main start

Code block end or Main end


27/27

End of lecture 1

Documents

C_Programming1