If Statement in C

Decision Control Statements

We frequently desire one set of instructions to be carried out in one circumstance while another set of instructions to be carried out in a completely different circumstance. A decision control instruction is used in C programs to handle situations of this nature.

By using decision control statements, we can direct the program's flow so that it executes specific statements based on the result of a condition.

We have the following decision control statements in the C programming language.

(a) The If statement

(b) The If-else statement

(c) The Conditional operators

In this article, we will talk about the if statement.

If Statement

When making judgments in C, the if statement is employed. A block of statements will be performed or not depends on whether the if statement has verified the specified condition and evaluated the outcome.

Syntax:

If(condition)
{
Statements;
// If the relational operator's conditions are met, statements will run.
}

An If statement is always followed by a condition enclosed in a pair of parentheses. The assertion is carried out if the condition is true. If the mentioned condition is not true, the statement will not be performed and the compiler skips over it.

Using C's "relational" operators is the norm when expressing a condition. In order to determine whether two values are equal to one another, different from one another, or greater than one another, we can compare them using relational operators.

If Statement Rules:

• The Boolean expression or Condition is always closed with the parenthesis.
  For an example, (x>=7).

• The Boolean expression or Condition will not be terminated by the semicolon (;). If this happens, the block of the statement will not execute even if the condition is true.
• The block of statements should be enclosed between the two curly braces.

Flow Diagram:

 The block of code enclosed by the if statement will be executed if this condition is satisfied. The if statement's inner block of code will not run if the condition is false.

Program-1:

#include<stdio.h>
int main( )
{
int number ;
printf ( "Enter a number less than 9:\n " ) ;
scanf ( "%d", &number ) ;
if ( number <= 9)
printf ( "What an intelligent student you are !\n" ) ;
}

Explanation:

• We have one integer-type variable named "number" in the main function.
• When the program runs, a message stating "Enter a number less than 9" will appear on the computer screen due to the printf function.
• The scanf function accepts keyboard input from the user.
• The compiler will arrive at the if condition after receiving input.
• If the condition is met, the compiler checks to see if the number is less than or equal to 9.
• If this criterion is met, the printf function will be executed, and the message "What a bright student you are!" will be displayed on the screen.
• But if the condition is not met, the printf function won't run, and the program will terminate.

Program Output:

If the condition is true then the following result will occur:-

If the condition is not satisfied then the result will occur:-

Program-2:

#include <stdio.h>
int main() {
    int negative_number;
    
    printf("When a condition is met, this programme will check which number is negative.\n");
    printf("Enter your any desired value: \n");
    scanf("%d", &negative_number);


    if (negative_number < 0) {
        printf("After condition is satisfied the value is: %d\n", negative_number);
    }


    return 0;
}

Explanation:

• We have one integer-type variable named " negative_number" in the main function.
• When the program runs, a message stating " When a condition is met, this programme will check which number is negative." will appear on the computer screen due to the printf function.
• After that, one more printf function executes, and we get a message “Enter your any desired value” on our computer screen.
• The scanf function accepts keyboard input from the user.
• The compiler will arrive at the if condition after receiving input.
• As if the condition meets, the compiler checks to see if the number is less than 0 or not.
• If this criterion is met, the printf function will be executed, and the message " After condition is satisfied the value is: " will be displayed on the screen.
• But if the condition is not met, the printf function won't run, and the program will terminate.

Program Output:

If the condition is true, then following result will occur:

If the condition is not satisfied, then following result will occur: