Decision making- If else statement

This statement is also a conditional statement. It starts with keyword ‘if’ followed by an expression followed by “ first statement”  and “ second statement” is given after ‘else’ clause.

Format:
if(expression)
statement1;
else
statement2;

if the expression is true then statement1 will be executed.
If the expression is false then statement2 will be executed.

Similarly, if there are more statement before ‘else’ then a block is to be formed and similarly if there are many statements after the ‘else’ clause then it’s separate block is formed.
Such statement is called “Compound if else” statement.

/*Program to check whether the number is odd or even and data is entered by the user*/

#include<stdio.h>
#include<conio.h>
void main()
{
     int n1;
     printf("\n enter any number");
     scanf("%d",&n1);
     if(n1%2==0)
     printf("number %d is even",n1);
     else
     printf("number %d is odd",n1);
     getch();
     }

/*Program to find which number is greater*/

#include<stdio.h>
#include<conio.h>
void main()
{
     int n1,n2;
     printf("\n enter 1st number");
     scanf("%d",&n1);
     printf("\n enter 2nd number");
     scanf("%d",&n2);
     if(n1>n2)
     printf("\n %d is greater than %d",n1,n2);
     else
     printf("\n %d is smaller than %d",n1,n2);
     getch();
     }

/*Program to enter item code, name, price, quantity by the user and calculate total amount that a customer have to pay*/

#include<stdio.h>
#include<conio.h>
void main()
{
     int itcd;
     char nm[40];
     float qty,pr,d,tamt,namt;
     printf("\n enter item name");
     scanf("%s",nm);
     printf("\n enter item code");
     scanf("%d",&itcd);
     printf("\n enter price and quantity(in Kg) of the item");
     scanf("%f%f",&pr,&qty);
     tamt=pr*qty;
     if(tamt>500)
     {
                 d=10;
                 namt=tamt-(tamt*10.0/100.0);
                 }
     else
     {
         d=5;
         namt=tamt-(tamt*5.0/100.0);
         }
     printf("\n discount on purchase is %f",d);
     printf("\n net amount given by customer is %f",namt);
     getch();
     }

/*Program to enter any number and check whether number entered is positive or negative*/

#include<stdio.h>
#include<conio.h>
void main()
{
     int n1;
     printf("\n enter any real number");
     scanf("%d",&n1);
     if(n1>=0)
     printf("\n number %d is positive",n1);
     else
     printf("\n number %d is negative",n1);
     getch();
     }

PRECAUTIONS

1. Use accurate header files.
2. Show proper expression in if statement.
3. End statement with ';'.
4. Declare the statements carefully using proper symbols.