C# for loops

Description

for loops are like while loops with special clauses for initialization and iteration of a loop variable.

Syntax

The syntax is:


for (initializer; condition; iterator) 
   statement(s) 

where:

  • initialization executes first and it if often used to declare the loop control value.
  • condition controls the loop body execution. If condition is false, C# starts executing the statement after the for loop.
  • iteration is executed after each loop iteration. iteration is usually used to update the loop-control variable.

Example

The following code uses the for loop the print the value from 0 to 9.


using System;//from  www. j  a v a2s .c  om

class Program
{
    static void Main(string[] args)
    {
        for (int i = 0; i < 10; i++)
        {
            Console.WriteLine(i);
        }

    }
}

The output:

Example 2

Example for nested for loop


using System; /*from   ww w.j  a  v a  2 s .  c  o  m*/
     
class MainEntryPoint 
{ 
   static void Main(string[] args) 
   { 
      // This loop iterates through rows 
      for (int i = 0; i < 100; i+=10) 
      { 
         // This loop iterates through columns 
         for (int j = i; j < i + 10; j++) { 
                   Console.Write(" " + j); 
         } 
         Console.WriteLine(); 
       } 
   }  
} 

The code above generates the following result.

Example 3

i is the loop-control variable. The scope of i is the for statement. You cannot use i outside.

We can put more variables in the initialization section.


using System;/*from  w  w w.  j  ava2  s.  c o  m*/

class Program
{
    static void Main(string[] args)
    {
        for (int i = 0, prevFib = 1, curFib = 1; i < 20; i++)
        {
            Console.WriteLine(prevFib);
            int newFib = prevFib + curFib;
            prevFib = curFib;
            curFib = newFib;
            Console.WriteLine(curFib);
        }

    }
}

The output:

Example 4

You can omit any parts of the for loop, the initialization, condition or iteration. The following example defines the loop-control variable outside for statement.


using System;//  ww  w  .  ja va2 s.c  om

class Program
{
    static void Main(string[] args)
    {
        int i = 0;
        for (; i < 10; i++)
        {
            Console.WriteLine(i);
        }
    }
}

The output:





















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