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C# For Loop

A for loop is a loop that gathers its start, its condition, and its change in one header. The header sits in parentheses after the for keyword.

Counting to five

The counter starts at 1 and grows by 1. The loop stops after printing 5.

using System;

class Program
{
    static void Main(string[] args)
    {
        for (int i = 1; i <= 5; i++)
        {
            Console.WriteLine(i);
        }
    }
}

Even numbers

The change part adds 2 on each pass. The counter prints the even numbers from 2 to 10.

using System;

class Program
{
    static void Main(string[] args)
    {
        for (int i = 2; i <= 10; i += 2)
        {
            Console.WriteLine(i);
        }
    }
}

Chars by index

The index counts from 0 up to the string length. Each pass prints the char at that index.

using System;

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

Example

using System;

class Program
{
    static void Main(string[] args)
    {
        for (int i = 1; i <= 3; i++)
        {
            Console.WriteLine("7 x " + i + " = " + (7 * i));
        }
    }
}

Key points

  • The header holds three parts split by semicolons.
  • The first part sets the starting value.
  • The second part is the condition checked before each pass.
  • The third part changes the counter after each pass.
  • An index in square brackets reads one char of a string.

In this example, i starts at 1. The first pass prints "7 x 1 = 7". The second pass prints "7 x 2 = 14". The third pass prints "7 x 3 = 21". The condition then fails and the loop stops.

Note

A for loop fits well when the count of passes is known in advance.

Try it Yourself

Edit the code, then press Run.

Running is simulated · Programiz C# Compiler

Exercise

Which part of a for header runs after each pass?