For

keyword used with "to"\"downto" and "do" to execute a loop in which the value of a control variable is incremented or decremented by 1 each time:

FOR control_variable := start TO final DO statement

which increases control_variable by 1 on each execution of the loop until the value is greater than or equal to final or

FOR control_variable := start DOWNTO final do statement

which decreases control_variable by 1 on each execution of the loop until the value is less than or equal to final

Where control_variable is the variable to be set to the value of start. The control variable is increased or decreased by 1 on each loop until its value reaches or exceeds final.

For I:=1 To 100 Do statement;

(repeats statement one hundred times, increasing I from 1 to 100)

  for I:=100 downto 1 do ''statement'';

(repeats statement one hundred times, decreasing I from 100 to 1)

• FOR will loop through only the single statement that follows it. To execute more than one statement, enclose the group of statements in a Begin/End block.
• In a for..to loop, if start is greater than final, the loop is not executed
• in a for..downto loop, if start is less than final, the loop is not executed

After the loop, the value of control_variable will be final. If the loop was not executed, the value of control_variable does not change.

• you can use types instead of numbers.

Keywords: begin — do — else — end — for — if — repeat — then — until — while