A Guide on Loops in C Programming- With Examples

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Looping Statements in C repeatedly execute statements until the specified condition becomes false. A loop in C consists of two components: the loop body and a control statement. The control statement is a set of requirements instructing the loop’s body to continue executing until the stated situation becomes false. In the C programming language, loop aims to achieve the same code repeatedly.

Types of Loops in C: What are Loops in C?

Depending on the position of a control statement in a program, there are two types of looping statements in C:

1. Entry-controlled loop

2. Exit controlled loop

In a C entry control loop, a condition is evaluated before running the loop’s body, additionally known as a pre-checking loop.

An exit-controlled loop evaluates a condition after the loop’s body has been executed and is additionally known as a post-checking loop.

Loop

The control conditions must be precisely defined and described; else, the loop will execute indefinitely. An endless loop is a loop that never stops performing and processes the statements several times. A continuous loop is another name for an infinite loop. Listed below are some attributes of an endless loop:

• No termination condition is indicated.
• The specified conditions are never satisfied.

The supplied state decides whether or not the loop’s body is executed.

The C programming language has three loop structures:

1. The while loop structure

2. The do-while loop

3. A for loop

What are Loops in C?

Sr. No	Loop Type	Description
1	While Loop	A condition is examined before executing the loop’s body in a while loop. If a condition is actual, the body of a loop is processed.
2	Do-While Loop	In a Do-while loop, the condition always follows the loop body. Also known as an exit-controlled loop.
3	For Loop	In a for loop, the initial value is executed only once. After each iteration, the condition tests and compares the counter to a fixed number, exiting the for loop when false is returned.

In this C++ Tutorial, you can learn more details:

While Loop in C 

A while loop is the simplest structure for looping. The while loop syntax in the C programming language is as follows:

Syntax of While Loop

while(condition){//code}

It is a loop controlled by the entrance. A condition is examined in a while loop before executing the loop’s body. If and only if a condition is proper, the body of a loop is executed. After the loop’s body completes, control returns to the beginning, the condition is evaluated, and the same procedure is repeated until the condition becomes false. As soon as the condition becomes false, the control exits the loop.

After leaving the loop, control is passed to the statements immediately following the loop. The body of a loop might include many ideas. If it contains simply a single sentence, curly brackets are optional. Even if there is only a single statement in the body, it is excellent practice to utilise curly brackets.

If the condition is false in a while loop, the loop’s body will not be executed even once. Do while loop is different, as we will see shortly.

Example: What loops in C/

#include<stdio.h>#include<conio.h>void main(){int i = 20;while( i <=20 ) {printf (“%d ” , i );i++;}getch();}

Out Put: 20

While Loop in the C Programming Language

In this C programming tutorial we have:

• We have assigned the value 1 to the num variable. We will print from 1 to 10; thus, we initialise the variable with the value 1. If you wish to print from 0, initialise the variable with the value 0.
• In a while loop, the condition (num = 10) indicates that the body will be executed until the value of num reaches 10. After that, the loop will end, and control will pass outside.
• In the loop’s body, we have a print function to output our number and an increment operation to increase the value with each iteration. The initial value of num is 1, which will become two after the execution and three during the subsequent execution. This operation will continue until the value reaches 10, at which point the series will get printed to the console, and the loop will end.
• The formatting character n indicates that the value will be written on a new line. Check out the C++ tutorial for more details.

Do-While loop in C 

The Do-while loop in C is similar to the while loop, except the condition is always run after the loop’s body. Also known as an exit-controlled loop.

Do while loop syntax in the C programming language is as follows:

Syntax of Do-While Loop in C:

do {  statements} while (expression);

The body is run if the condition is true, as seen in a while loop. Sometimes, the loop’s body must be executed at least once, even if the condition is false. This procedure can be accomplished using a do-while loop.

The body of a loop is always run at least once in a do-while loop. After the body is executed, the condition is examined. If the condition is met, the loop’s body will be executed again; otherwise, control will exit the loop.

Similar to the while loop, the sentences immediately after the loop are performed when the control exits the loop.

The essential distinction between the while and do-while loops is written at the beginning of the while loop. The while condition is written at the end of a do-while loop and terminates with a semicolon (;). C programming tutorial will help you to explore the topics.

The following C loop program demonstrates how a do-while loop operates:

#include<stdio.h>#include<conio.h>int main(){ int num=1; //initializing the variable do //do-while loop  { printf(“%d\n”,2*num); num++; //incrementing operation }while(num<=10); return 0;}

Output

Output: 2468101214161820

In this C programming tutorial, we have:

• First, we have assigned the value 1 to the variable ‘num.’ We then created a do-while loop.
• In a loop, we have a print function that multiplies the value of num by two before printing the series.
• The value of num will rise by one after each increment and be displayed on the screen.
• The initial value of num is 1. In the loop’s body, the print function will be executed as follows: 2*num when num = one yields 2*1 = 2. It will continue till the num’s value becomes 10. In this instance, return 0. Check out the C++ tutorial for more details.

For loop in C

In C programming language, a For loop is a more efficient loop type. The general syntax structure of C for loops is as follows:

Syntax of For Loop in C: What are Loops in C?

for ( starting value; condition; incrementation or decrementation ) {  statements;}

• The first value of the for loop only occurs once.
• The situation is a Boolean expression that compares the counter to a constant number after each iteration.
• The increment/decrement operation increases (or reduces) the counter by a predetermined amount.

Example: What is Loops in C?

#include<stdio.h>int main(){ int number; for(number=1;number<=10;number++) //for loop to print 1-10 numbers { printf(“%d\n”,number); //to print the number } return 0;}

Output:12345678910

In this C programming tutorial, we have:

• We have declared an integer variable for storing values.
• In the for loop’s initialization section, the variable number has the value 1. In the condition section, we supplied our condition, followed by the increment section.
• Within the body of a loop, we have a print function that outputs the numbers to the console on a new line. The variable number contains the value one; after the first iteration, the variable’s value will increase and become 2. Now the value of the variable number is 2. This loop will continue to manage until the variable’s value reaches 10.

• In C, the for loop can include numerous expressions separated by commas. Check out the C++ tutorial for more details.

The nesting of for loops is possible at any depth.

Break Statement in C

the break is primarily used within the switch statement. It is also helpful in stopping a loop immediately.

Consider the following program, which uses a break statement to end a while loop:

#include <stdio.h>int main() {int num = 5;while (num > 0) {  if (num == 3)    break;  printf(“%d\n”, num);  num–;}}

Output: 54

Continue Statement in C

Use the continue statement to jump to the next iteration while remaining in the loop.

Syntax: What is Loops in C?

#include <stdio.h>int main() {int nb = 7;while (nb > 0) {  nb–;  if (nb == 5)    continue; printf(“%d\n”, nb);}}

 Output

64321

 5 is skipped in this program

Which Loop to Choose?

Loop selection is always a complex problem for programmers; to select a loop, follow these steps:

• Analyze the issue and determine whether a pre-test or post-test loop is required.
• If a post-test is required, a while loop should be used.

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Synopsis: What is Loops in C?

1. Define loop in C: A Loop is one of the most fundamental programming notions. One can implement Loops using conditional statements in the C programming language.
2. C block of loop control instructions is performed until the condition turns false the specified number of times.
3. C programming has two sorts of loops: entry-controlled and exit-controlled.
4. List several loop control commands in C: C programming, including 1) while, 2) do-while, and 3) instructions for controlling loops.
5. C’s Do-while statement is an exit control loop.

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