Loops in C

Level : Beginner
Mentor: Shailendra Chauhan
Duration : 00:05:00

What are Loops in C?

Loops are control structures in C that allow you to execute a block of code continuously as long as a specific condition is met. They help in creating more efficient and concise code.

Need for Looping Statements in C

  • Loops enable the user to repeat the same collection of statements without having to write the same code several times.
  • It saves time, and effort, and improves efficiency.
  • It lowers the possibility of finding mistakes during compilation.
  • Loops make code more clear and understandable, particularly when dealing with complex logic or big data sets.
  • It promotes code reuse.
  • Loops are useful for traversing data structures like arrays or linked lists.

Types of Loop in C

There are 3 Types of Loops in C:

  1. for loop
  2. while loop
  3. do while loop

For Loop

A for loop is a control structure that allows a sequence of instructions to be performed for a predetermined number of iterations. It's an entry-controlled loop. It has three sections: index declaration, condition (boolean expression), and update statement. The for loop is useful when you know the precise number of iterations.


How does the for loop work?

  • The initialization statement is only used once.
  • Next, the test expression is evaluated. If the test expression returns false, the for loop is terminated.
  • If the test expression is true, the statements in the for loop's body are executed, and the update expression is updated.
  • Again, the test expression is examined.
  • This operation continues until the test expression is false. When the test expression is false, the loop ends.

Infinite For Loop

An infinite loop refers to a loop that runs continuously. In short, in the for loop, if the test condition (check_condition) is not specified, it is presumed to be true by default. As a result, the condition never turns false.

Advantages of the For Loop

  • Allows code reusability.
  • The code size decreases.
  • Traversing data structures such as arrays and strings becomes simple.

Disadvantages of using For Loops

  • Cannot skip any elements while traversing.
  • Only one requirement is followed.

While Loop

A while loop executes a statement or a group of statements until the provided expression returns false. The while loop is useful when you don't know the exact number of iterations.


Working of the While Loop

  • When the program first enters the loop, the test condition will be assessed.
  • If the test condition is false, the loop's body is skipped and the program continues.
  • If the expression returns true, the body of the loop will be run.
  • After executing the body, the program will proceed to the first step. The operation will continue till the test expression is true.

Infinite While Loop in C

In C programming, an infinite while loop is a loop structure that executes endlessly until it encounters a break statement or a condition that terminates it. It is referred to as "infinite" because, unlike other loops, it has no fixed ending.

Do While Loop

A Do While loop is similar to a while loop, but it evaluates the expression after the code block is executed.​ Always executes at least once. Useful for one-time execution with conditional dependencies.


How does the Do-While Loop work?

  • The do-while loop executes the body first before checking the test condition, unlike other loops that verify the test condition first.
  • The do-while loop, also known as the exit-controlled or post-tested loop, is named for this attribute.
  • When the test condition is true, the program control returns to the beginning of the loop, and the body is executed once more.
  • This method is repeated until the test condition is met.
  • When the test condition is false, the program moves on to the next sentence after the do-while loop.

Advantages of Do While Loop

  • A do-while loop has a simple structure that everybody can understand.
  • Regardless of the condition, the code inside a do-while loop gets run at least once in its lifetime.
  • The code inside a do-while loop will continue to run until the condition is met.


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