The FOR keyword.

• Basic principles.
• Repeating several lines of code
• More detail

Basic principles

Say you wanted to print all the numbers between 1 and 10, you could write:

	main()
        {
	   int count=1;

	   printf("%d\n", count++);
	   printf("%d\n", count++);
	   printf("%d\n", count++);
	   printf("%d\n", count++);
	   printf("%d\n", count++);
	   printf("%d\n", count++);
	   printf("%d\n", count++);
	   printf("%d\n", count++);
	   printf("%d\n", count++);
	   printf("%d\n", count++);
        }

As you can see this program would NOT be very practical if we wanted 1000 numbers. The problem can be solved with the for statement as below.

	main()
        {
	   int count;

           for ( count=1 ; count <= 10 ; count++) printf("%d\n", count); } 

count=1

is the initalisation.

count <= 10

An expression. The for statement continues to loop while this statement remains true

count++

increament or decreament.

printf("%d\n", count)

the statement to execute.

Repeating several lines of code

	main()
        {
	   int count, sqr;

           for ( count=1 ; count <= 10 ; count++) { sqr=count * count; printf( " The square of"); printf( " %2d", count); printf( " is %3d\n", sqr); } } 

More detail

	for (expression_1 ; expression_2 ; expression_3) statement ;

1. Executes expression_1.

2. Executes statement.
3. Executes expression_3.
4. Evaluates expression_2.
   • If TRUE, Jumps to item 2.
   • If FALSE, Stops looping.

	main()
	{
	   for( ; ; ) puts(" Linux rules!");
	}

Examples:

See also:

• while keyword.
• do keyword.
• continue keyword.
• break keyword.
• for got_ya.