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LOOPS in C++

Mayank Mandhana

April 30, 2021

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C++ Loops

There may be a situation when we need to execute a block of the program several times. Therefore, In a programming language, loops are used when we need to execute a block of statements repeatedly.

The following is the general from of a loop statement:

There are mainly two types of Loops:

1. Entry Controlled loops: The test condition is tested before entering the loop body. While Loop and For Loop is entry-controlled loops.
2. Exit Controlled Loops: The test condition is tested at the end of the loop body. Hence, the loop body will execute at least once, irrespective of whether the test condition is true or false. The do-while loop is exit controlled loop.

Concept of Loop statements

C++ While Loop

Syntax:

while (condition) 
{
    // body of the loop
}

• A while loop assess the condition
• If the condition assessment is true, the code inside the while loop is executed.
• Then the condition is assessed again.
• This process continues until the condition assessment is false.
• When the condition assessment is false, the loop terminates.

C++ for LOOP

for (initialization; condition; update) 
{
    // body of-loop 
}

Here,

• initialization – Variable is initialized and is executed only once
• condition – If the assessment of the condition is true, the body of for loop is executed and
  if false, the for loop gets terminated
• update – Updates the value of initialized variables and checks the condition again

C++ do…while loop

Here,

• At first, the body of the loop is executed. Then the condition is evaluated.
• If the evaluation of the condition is true, the body of the loop inside the do statement is executed again.
• The condition is evaluated again.
• If the condition assessment is true, the body of the loop inside the do statement is executed again.
• This process keeps repeating until the condition evaluates to false. Then the loop terminates.

Loop Control Statements

Loop control statements change the execution of the program from their normal sequence.

Following are the control statements in C++:

The Infinite Loop

A loop becomes an infinite loop if the evaluation of the condition is never false.

Example:

#include <iostream>
using namespace std;
int main(){
   for(int i=1; i>=1; i++){
      cout<<"GeeksGod"<<endl;
   }
   return 0;
}

OUTPUT
------
GeeksGod
GeeksGod
GeeksGod
GeeksGod
GeeksGod
GeeksGod
GeeksGod
...

Also,

#include <stdio.h>

int main()
{
    for(;;)  // Absent Condition
    {
    printf("GeeksGod\n");
    }
    return 0;
}

When the conditional expression is absent, it is assumed to be true.