C Inroduction

 C Programming

What is C?

• C is a programming language developed at

AT & T’s Bell Laboratories of USA in 1972.

• It was designed and written by a man named

Dennis Ritchie.

• Major parts of popular operating systems like

Windows, UNIX, Linux is still written in C.

Steps in Learning C

The C Character Set

• A character denotes any alphabet, digit or

special symbol used to represent information.

• Alphabets

– *A,B, ... . . , Y, Z, a, b, ... ... , y, z+

• Digits

– *0, 1, 2, 3, 4, 5, 6, 7, 8, 9+

• Special symbols

– *~

‘ ! @ # % ^ & ∗ ( ) _ − + = | * + , - ∶ ;

" ′ < >

, . ? /+

Constants, Variables and Keywords

• constants, variables and keywords are formed

with the help of alphabets, numbers and

special symbols.

Types of C Constants

Integer Constants

• An integer constant

– must have at least one digit.

– must not have a decimal point.

– can be either positive or negative.

– can have no commas or blanks.

• Example:

– 426

– +782

– -8000

– -7605

Real Constants

• A real constant

– must have at least one digit.

– can have a decimal point.

– could be either positive or negative.

– default sign is positive.

– must not have commas or blanks.

• Example:

– +325.34

– 426.0

– -32.76

– -48.5792

Character Constants

• A character constant is a single alphabet, a single

digit or a single special symbol enclosed within

single inverted commas.

• The maximum length of a character constant can

be one character.

• Example

– 'A'

– 'I'

– '5'

– „@'

Types of C Variables

• Following are commonly used primary data

types in C language

– Integers (int)

– Real Numbers (float, double)

– Characters (char)

Rules for Constructing Variable Names

• A variable name is any combination of 1 to 31

alphabets, digits or underscores.

• The first character in the variable name must

be an alphabet or underscore (_).

• No commas or blanks are allowed within a

variable name.

• No special symbol other than an underscore

(_) (as in gross_sal) can be used in a variable

name.

C Variables

• Which of the following variable names are

correct

– si_int(correct)

– emp_hra(Corr.)

– cart_e_89 (correct)

– 23alpha (incorrect0

– Beta-gama (incorrect)

– ____theta (correct)

– calory

C Variables

• These rules remain same for all the types of

primary and secondary variables (arrays, string,

structure, union etc.).

• It is compulsory for you to declare the type of any

variable name that you wish to use in a program.

• Examples

– int age;

– float salary;

– char grade;

C Keywords

• Keywords are the words with special meaning

that has already stored in the C compiler.

• The keywords cannot be used as variable

names.

• There are 32 keywords in the C language.

C Keywords

A simple addition program

#include<stdio.h>

int main( )

// main() is the function where execution starts

{

int num_1, num_2, sum ;

num_1=34;

num_2=45;

sum = num_1+num_2;

printf("%d\n",sum);

}

printf() Function

• The general form of printf( ) function is

printf ( "<format string>", <list of variables> ) ;

• <format string> can contain

– %f :for printing real values.

– %d :for printing integer values.

– %c :for printing character values.

– Printf(“%f”, salary);

Input from Keyboard

#include<stdio.h>

int main()

{

int num_1, num_2, sum;

scanf("%d", &num_1);

scanf("%d", &num_2);

sum = num_1+num_2;

printf("%d\n",sum);

}

scanf() Function

• scanf() is the function used for taking input

from keyboard.

scanf ( "<format string>", &<variable> ) ;

A Simple Interest program

#include<stdio.h>

int main( )

{

int p, n ;

//p- Pricnciple Amount

//n- number of years

float r, si ;

//r-rate of interest

//si- simple interest

p = 1000 ;

n = 3;

r = 8.5;

/* formula for simple interest */

si = p * n * r / 100 ;

printf ( "%f\n" , si ) ;

}

A Simple Interest Program with

Keyboard Input

#include<stdio.h>

int main( )

{

int p, n ;

//p- Pricnciple Amount

//n- number of years

float r, si ;

//r-rate of interest

//si- simple interest

scanf ( "%d %d %f", &p, &n, &r ) ;// taking input from keyboard

/* formula for simple interest */

si = p * n * r / 100 ;

printf ( "%f\n" , si ) ;

}