C# 0 The Complete Reference

i

 and 

j

 are initialized. Each time the loop repeats, 

i

 is incremented 

and

j

 is decremented. Multiple loop control variables are often convenient and can simplify 

certain algorithms. You can have any number of initialization and iteration statements, but 

in practice, more than two make the 

for

 loop unwieldy.

Here is a practical use of multiple loop control variables in a 

for

 statement. This 

program uses two loop control variables within a single 

for

 loop to find the largest and 

smallest factor of a number, in this case 100. Pay special attention to the termination 

condition. It relies on both loop control variables.

// Use commas in a for statement to find the largest and

// smallest factor of a number.

using System;

class Comma {

  static void Main() {

    int i, j;

    int smallest, largest;

    int num;

    num = 100;

    smallest = largest = 1;

    for(i=2, j=num/2; (i <= num/2) & (j >= 2); i++, j--) {

      if((smallest == 1) & ((num % i) == 0))

        smallest = i;

      if((largest == 1) & ((num % j) == 0))

        largest = j;

    }

    Console.WriteLine("Largest factor: " + largest);

    Console.WriteLine("Smallest factor: " + smallest);

  }

}

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Here is the output from the program:

Largest factor: 50

Smallest factor: 2

Through the use of two loop control variables, a single 

for

 loop can find both the smallest 

and the largest factor of a number. The control variable 

i

 is used to search for the smallest 

factor. It is initially set to 2 and incremented until its value exceeds one half of 

num

. The 

control variable 

j

 is used to search for the largest factor. Its value is initially set to one half 

the

num

 and decremented until it is less than 2. The loop runs until both