for loop

• General form of for loop

      for (initial; condition; increment)
        {
         statement;
        }
  

• Example:

      for (i = 0; i < 10; i++)
        printf("%d\n", i);
    

  There is only 1 statement inside of the loop, so you can omit { }.

• What actually happens:
  1. initial is evaluated.
  2. condition is evaluated.
  3. If condition is NOT met, the for loop terminates, and the process moves to the next statement after statement.
  4. If condition is met, statement is executed.
  5. increment is evaluated, and goes to step 2

• Statement and block (a compound statement)

  for (i = 0; i < 10; i++)
  {
    squared = i * i;
    printf("%d\n", squared);
  }
  

  Frequently, you need to have multiple statements within a loop.
  A block is a group of 2 or more statements enclosed in braces.
  See the source code for the immigration-emigration process.

• Nested Loop

  for (i = 5; i > 0; i--) 
  {
    for (j = 0; j < 3; j++) {
      printf("i = %d, j = %d\n", i, j);
    }
  
    printf("End of the outside loop\n");
  }
  

• Exercises:
  
  1. Guess the results of following loops:

     1.   for(i=0, j=10; i<3; i++, j--)
             printf("%d\n", i+j);
        

     2.   i = 0;
          for( ; i<3; printf("\n")) {
             printf("%d", i);
             i++;
          }
        

     3.   for(i=0; i<3; j++)
             printf("%d\n", i);
        

     4.   for(i=0; i<10; i--)
             printf("%d\n", i);
        

     5.   for(i=0; i<10; i--);
             printf("%d\n", i);
        

  2. Make a program to calculate 18!. x! (factorial) is defined as x! = x * (x-1) * .... * 2 * 1