C Loops
What are Loops in C?
Loops are used to execute a block of code repeatedly until a specified condition becomes false.
They help reduce code repetition and make programs more efficient.
Instead of writing the same statement multiple times, a loop can execute it automatically.
Example
for(int i = 1; i <= 5; i++)
{
printf(“%d\n”, i);
}
Explanation
• for loop repeats the code multiple times.
• i starts from 1.
• The loop continues until i becomes greater than 5.
• i++ increases the value of i by 1 in each iteration.
• The output will display numbers from 1 to 5.
Why Loops are Important?
Loops are important because they:
• Reduce code repetition.
• Save programming time.
• Make programs shorter and easier to maintain.
• Help perform repetitive tasks efficiently.
• Improve code readability.
Types of Loops in C
C provides three types of loops:
• for Loop
• while Loop
• do-while Loop
Each loop is used to execute a block of code repeatedly based on a condition.
for Loop
The for loop is used when the number of iterations is known in advance.
Syntax:
for(initialization; condition; increment/decrement)
{
// code
}
Example
for(int i = 1; i <= 5; i++)
{
printf(“%d\n”, i);
}
Explanation
• Initialization runs only once.
• Condition is checked before every iteration.
• Increment updates the loop variable.
• The loop prints numbers from 1 to 5.
while Loop
The while loop is used when the number of iterations is not known in advance.
The loop continues until the specified condition becomes false.
Syntax:
while(condition)
{
// code
}
Example
int i = 1;
while(i <= 5)
{
printf(“%d\n”, i);
i++;
}
Explanation
• The condition is checked before each iteration.
• The loop executes while the condition is true.
• i++ increases the value of i by 1.
• The loop prints numbers from 1 to 5.
do-while Loop
The do-while loop executes the code at least once before checking the condition.
The condition is checked after the execution of the loop body.
Syntax:
do
{
// code
}
while(condition);
Example
int i = 1;
do
{
printf(“%d\n”, i);
i++;
}
while(i <= 5);
Explanation
• The loop body executes first.
• The condition is checked after execution.
• The loop runs at least one time even if the condition is false.
• The loop prints numbers from 1 to 5.
Comparison of Loops
• for Loop → Used when the number of iterations is known.
• while Loop → Used when the number of iterations is not known.
• do-while Loop → Executes at least once before checking the condition.
Example Program
Program
#include <stdio.h>
int main()
{
int i;
for(i = 1; i <= 5; i++)
{
printf(“%d\n”, i);
}
return 0;
}
Output
1
2
3
4
5
Explanation
• int i; → Declares a loop variable.
• i = 1 → Initializes the loop.
• i <= 5 → Condition that controls the loop.
• i++ → Increases the value of i by 1 after each iteration.
• printf() → Displays the value of i.
• The loop prints numbers from 1 to 5.
Key Points
• Loops are used to execute a block of code repeatedly.
• Loops reduce code repetition and improve efficiency.
• C provides three types of loops: for, while, and do-while.
• for loop is used when the number of iterations is known.
• while loop is used when the condition controls the loop.
• do-while loop executes at least one time.
• Proper use of loops makes programs shorter and easier to maintain.