C++ - For Loop

The for loop executes a set of statements in each iteration. Whenever, number of iteration is known, for loop is preferred over while loop.

Syntax

for(initialization(s); condition(s); counter_update(s);){
  statements;
}

Initialization(s): Variable(s) is initialized in this section and executed for one time only.
Condition(s): Condition(s) is defined in this section and executed at the start of loop everytime.
Counter Update(s): Loop counter(s) is updated in this section and executed at the end of loop everytime.

Flow Diagram:

Example:

In the example below, the program continue to print variable called i from value 1 to 5. After that, it exits from the for loop.

#include <iostream>
using namespace std;
 
int main (){
  for (int i = 1; i <= 5; i++){
    cout<<i<<"\n"; 
  }
  return 0;
}

The output of the above code will be:

Example

Multiple initializations, condition checks and loop counter updates can be performed in a single for loop. In the example below, two variable called i and j are initialized, multiple conditions are checked and multiple variables are updated in a single for loop.

#include <iostream>
using namespace std;
 
int main (){
  for (int i = 1, j = 100;   i <= 5 || j <= 800;   i++, j = j + 100){
    cout<<"i="<<i<<", j="<<j<<"\n"; 
  }
  return 0;
}

The output of the above code will be:

i=1, j=100
i=2, j=200
i=3, j=300
i=4, j=400
i=5, j=500
i=6, j=600
i=7, j=700
i=8, j=800