C Programming If Statement: Syntax and Practical Examples
In a C program, the if statement is a decision making statement that determines whether a block of code executes based on a given condition or the value of an expression. It is one of the most simple and important control statements in the C language. Using the if statement, the flow of program execution can be changed or modified.
It decides whether a certain statement or block of statements will be executed or not; that is, if a given condition is true, then the statements or block of statements are executed; otherwise, they are not.
The if statement allows code to be executed conditionally based on a boolean expression. It makes the code more readable and enables the programmer to reuse code in different parts of the program.
If statements help in simplifying problem solving and debugging within specific code blocks. They give the programmer flexibility to control the flow of execution.
In summary, the if statement in C programming is a fundamental tool for controlling program flow based on conditions. Its advantages include flexibility, reusability and readability.
Syntax : if statement
if (condition)
{
/* statements to execute if condition is true */
}
The condition in the above syntax evaluates to either true or false. True is represented by a non-zero value (e.g., 1), and false is represented by zero (0).
The statements inside the curly braces {} can be a single statement or multiple statements.
Given Diagram is for the syntax and flowchart of the if statement. Let's learn how the syntax (if statement) works from the given diagram. We know that program execution starts from the top and goes to the end. After step-by-step successful execution of the program, the control falls into the if block. Then, the flow jumps to the condition and starts testing the condition.
1. If the condition tested is true (or its result is true), then it executes the statements inside the if body, i.e., the statements to be executed when the condition in the if is true. After successful execution of these statements, the control comes out of the if block and executes the code "statements outside the if."
2. If the condition tested is false, then the code outside the if executes—that is, the "statements outside the if" always execute regardless of whether the condition is true or false.
Example 1: C program to illustrates the use of if statement .
#include<stdio.h>
int main()
{
int x=10;
int y=2;
if(x<y) /* Test condition to check if x is less than y */
{
printf("\n %d is smaller than %d",x,y);
}
if(y<x) /* Test condition to check if y is less than x */
{
printf("\n %d is smaller than %d",y,x);
}
return 0;
}
Output:
2 is smaller than 10
The above program demonstrates the use of if statements to determine which number is smaller. In the program, two integer variables, x and y are declared and initialized with values 10 and 2, respectively. The first if statement uses the relational operator < to check if x is less than y, since this condition is false, no output is produced. The second if checks if y is less than x, which is true, so it prints "2 is smaller than 10." After executing, the program terminates successfully.
Example 2: C program to test if a given number is even or odd
#include <stdio.h>
int main()
{
int n;
printf("\nEnter Any Number: ");
scanf("%d", &n);
/* Check if the number is even */
if (n % 2 == 0)
{
printf("\n%d is Even\n", n);
}
/* Check if the number is odd */
if (n % 2 != 0)
{
printf("\n%d is Odd\n", n);
}
return 0;
}
Enter Any Number
5
5 is Odd
Program Explanation:
In C, dividing two integers results in an integer value, truncating any fractional part.
For example, 7/2 results in 3, not 3.5. To determine if a number is even or odd, the program uses the modulus operator %.
Even numbers are multiples of 2 and satisfy n % 2 == 0, whereas odd numbers satisfy n % 2 != 0.
After reading the input into variable n, the program checks these conditions: if n % 2 == 0, it prints that n is even.
if n % 2 != 0, it prints that n is odd.
For input 5, the first condition is false and the second is true so it outputs "5 is Odd."
