In C programming, the ‘do’ keyword is an essential component of ‘do-while’ loops. This article provides a comprehensive explanation of the ‘do’ keyword, its role in loop construction, and includes real-world examples to illustrate its significance in creating versatile and efficient loops.
Understanding the ‘do’ Keyword
The ‘do’ keyword in C is used to initiate a ‘do-while’ loop, which is a type of loop that guarantees the execution of the loop body at least once, regardless of the condition. ‘do-while’ loops are particularly useful when you need to ensure that a block of code is executed before checking the loop condition.
Syntax for ‘do-while’ Loop:
do {
// Code inside the loop body
} while (condition);
Example 1: Using ‘do’ in a ‘do-while’ Loop
#include <stdio.h>
int main() {
int i = 1;
do {
printf("%d ", i);
i++;
} while (i <= 5);
return 0;
}
Output:
1 2 3 4 5
In this example, the ‘do-while’ loop is used to print the values of i from 1 to 5. The loop body is executed first, and then the condition i <= 5 is checked. Because the condition is true, the loop continues to execute until the condition becomes false.
Use Cases for ‘do’ and ‘do-while’ Loops
- Input Validation: ‘do-while’ loops are suitable for input validation, ensuring that user input meets certain criteria before proceeding.
- Menu-Driven Programs: They are useful in menu-driven programs where the menu should be displayed at least once, and the user can choose to continue or exit.
Example 2: Input Validation using ‘do-while’ Loop
#include <stdio.h>
int main() {
int number;
do {
printf("Enter a positive number: ");
scanf("%d", &number);
} while (number <= 0);
printf("You entered a positive number: %d\n", number);
return 0;
}In this example, the ‘do-while’ loop ensures that the user enters a positive number. The loop continues to prompt the user until a positive number is provided.
