for Loops

• A for loop is also called a counting loop, because it repeatedly executes a block of code a certain number of times. The basic syntax for a for loop is: :

for (counter = initial-expression; logical-expression; change-counter)
        statement

• Execute the counter = initial expression. This happens only the first time through the loop.
• Evaluate the logical expression:

  If it is true

  • Execute the statement inside the for loop.
  • Return to the top of the loop and execute the change-counter part.
  • Then back to "Evaluate the logical expression."
• This is repeated until the logical expression evaluates to false, then execution falls through to the next statement.
• The statement repeated by the for loop can also be a compound statement:

for (counter = initial-expression; logical-expression; counter-change)
{
    statement
    statement
    ...
}

• A real section of code is a little clearer:

  for (i = 1; i <= 10; i++)
  {
      statement
      statement
      ...
  }
  

• In the for loop above, the statements will be repeated how many times?

• The first part of the for loop, i = 1; initializes the object i to the value 1.

• The next part, i <= 10; contains the logical expression that will be evaluated each time through the loop. The loop will continue until this expression evaluates to false.
• The last part, i++ increments i by adding 1 to it (it could also have been written as i = i + 1 or i += 1).
• At the conclusion of the loop, i has the value 11.
• Typically, the variable i should be of type int, but for loops can be written with floats or doubles, if appropriate.
• You can change the counter in any way you would like. For instance, you could write a for loop that counts by 5s:

for (i = 5; i <= 30; i = i + 5)
    statement

• You can also use a for loop that counts down. How would you do it?