if in C

if statement in C programming, How to use if condition in C

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In C programming if statement is used to check whether the given condition is true or not, if condition is true then the scope of if statement will be executed otherwise it will be skipped by the compiler.

if Statement Syntax


if(condition)
{
// scope of if statement or if block
}

if statement is used to check only one condition at a time.
In a single C program, we can use more than one if statement.
if condition/expression is true then the scope of the if statement will run.
if condition/expression is false then the scope of the if statement will not run.

Example

#include<stdio.h>
 int  main()
  {
     int m=10, n=2, res;
     res=m+n;
     if(m>n)
     {
       printf("m is bigger than n \n");
     }
     if(n>m)
     {
       printf("n is bigger than m \n");
     }
     printf("m+n = %d\n",res);
     return 0;
  }

Output


m is bigger than n
m+n = 12

Value of Condition / Expression

In decision making statements when we say condition or expression, the meaning of both is the same so don't be confused between the condition and expression.

In decision making, if the given condition is true then the value of condition/expression is 1
In decision making, if the given condition is false then the value of condition/expression is 0
In if expression a non zero number is always treated as truth whereas zero is treated as false.

Example

int a=20, b=30, c=40;
the value of (a>b) is 0
the value of (b>a) is 1
the value of (b>c) is 0
the value of (a<c) is 1

Example

#include<stdio.h>
 int  main()
  {
     int m=10, n=2, res;
     res=m+n;
     if(1)
     {
       printf("Message from if 1 \n");
     }
     if(0)
     {
       printf("Message from if 0 \n");
     }
     if(m>n)
     {
       printf("m is big \n");
     }
     if(m<n)
     {
       printf("n is big \n");
     }
     printf("m+n = %d\n",res);
     return 0;
  }

Output

Message from if 1
n is big
m+n = 12

Combined Condition in if Statement

In if expression more than one condition can be combined together by using logical operators &&, ||, !

if(a>b && a<50)

if(a<b || a< 25)

if(!(a>b))

Example

A father promises his son that if he is 18+ and gets more than 60% marks in his exam, they will give him a bike, now write a C program which can check that his son is eligible for the bike or not.

#include<stdio.h>
 int  main()
  {
     int age, marks;
     printf("Enter age of student \n");
     scanf("%d", &age);
     printf("Enter marks of student \n");
     scanf("%d", &marks);
     
     if( (age>18) && (marks>60))
     {
       printf("Your son is eligible for bike");
     }
     if(!((age>18) && (marks>60)))
     {
       printf("Your son is not eligible for bike \n");
     }
     return 0;
  }

Output

Enter age of student 
19
Enter marks of student
76
Your son is eligible for bike

Note: Logical operator ! is used to convert true condition into false and false into true.

Let's take some real-time problem solutions with if condition in C programming.

Program 1

Make a simple arithmetic calculator by using if statement in C programming.

#include<stdio.h>
 int  main()
  {
     int n1, n2, n3, res;
     printf("Enter first number \n");
     scanf("%d", &n1);
     printf("Enter second number \n");
     scanf("%d", &n2);
     printf("For + enter 1\n");
     printf("For - enter 2\n");
     printf("For * enter 3\n");
     printf("For / enter 4\n");
     scanf("%d", &n3);
   
     if(n3==1)
     {
       res=n1+n2;
       printf("Sum = %d",res);
     }
     if(n3==2)
     {
       res=n1-n2;
       printf("Sub = %d",res);
     }
     if(n3==3)
     {
       res=n1*n2;
       printf("Mul = %d",res);
     }
     if(n3==4)
     {
       res=n1/n2;
       printf("Div = %d",res);
     }
     return 0;
  }

Output

Enter first number
22
Enter second number
7
For + enter 1
For - enter 2
For * enter 3
For / enter 4
1
Sum = 29

Note: There are no fixed and hard rules to use if condition in C programs, it depends on you how do you want to use if condition.

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if in C

if statement in C programming, How to use if condition in C

if Statement Syntax

Example

Output

Value of Condition / Expression

Example

Example

Output

Combined Condition in if Statement

Example

Output

Program 1

Output

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