Variables

Variables are temporary memory locations that we use to work with mathematical values.  Example-:int a,b,c;. In C variables must belong to a data type.

Data types in C

In C data type is a property that we add to our variables and finally our variables begin to behave like that data type.

The main data types in C are the following.

1. integer    -:To store integer values.
2. float        -:To store fractional values.
3. character-:To store character values.

However, C supports the following data types in all.

Working with data types:-

In C language data types are used especially in declaring variables. A variable must belong to a data type.

Declaration of variables

When we start main function our first task is to declare variables.
Synatax -:[datatype][set of variables];

Example-:int a,b,c;

Here int is a data type.

Rules for creating variable names.

• Variables name can be alphanumeric but the start of variables names can never be numeric.
• Only dash is allowed ( _ ).
• Keywords can never be used as variables.
• Since, C is a case sensitive language we should avoid capital letters.

Assigning values to variables.

Syntax -:
int a;   a=32000;
float x;   x=3.7;
char z;  z='*';

Write a C program for calculating Simple Interest.

#include< stdio.h>
#include< conio.h>
void main()
{
int p,t;
float r,si;
p=6000;
t=3;
r=7.8;
si=(p*r*t)/100;
printf("the si is %f",si); getch();
}

Displaying values of Variables.

When we have to display the value of a variaable we will have to use the printf() statement in a different way. Syntax -: printf(" ", )
Example-:
int a;
float b;
printf("%d%f",a,b);

Write a C program that input three sides of a triangle and displays the area of the triangle.

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

float a,b,c,s,ar;
a=15;
b=10;
c=5;
s=(a+b+c)/2;
ar=(s*(s-a)*(s-b)*(s-c));
ar=sqrt(ar);
printf("the area is %f",ar);
getch();
}

Write a C program to convert celsius to fahreinheit.

#include< stdio.h>
#include< conio.h>
void main()
{
float c,f;
printf("enter the temperature in celsius");
scanf("%f",&c);
f=(9*c+160)/5;
printf("the temperature in fahrenheit is %f",f);
getch();
}

Write a C program to calculate roots of Quadritic equation.

#include< stdio.h>
#include< conio.h>
void main()
{
int x,y;
float a,b,c,alp,bit;
a=3;
b=8;
c=4;
x=(b*b)-(4*a*c);
y=sqrt(x);
alp=((-b)+y)/(2*a);
bit=((-b)-y)/(2*a);
printf("the value of alpha is %f",alp);
printf("the value of alpha is %f",bit);
getch();
}