Purpose

FOR TO ENDFOR controls execution of a loop.  A loop is a construct containing a statement or block of statements that is executed repeatedly until a certain condition is met.
 

Syntax

FOR control-variable = initial-value TO final-value {BY increment/decrement} ENDFOR

or

FOR control-variable = initial-value DOWNTO final-value {BY increment/decrement} statement or block  
ENDFOR
 

Operation

control-variable must be a numeric variable.

initial-value is any numeric literal or expression that represents the start value of the loop counter.  This is computed only once, upon entry to the FOR loop and control-variable is initialized to this value.

final-value is any numeric literal or expression that represents the end value of the loop counter.  This is computed before each iteration of the loop.

increment/decrement is any numeric literal or expression representing the number by which initial-value is to be incremented/decremented at each iteration of the loop.  The default is 1.
 

Remarks

If a statement in the loop changes the value of increment, decrement, final-value, or control-variable, the number of times the loop is executed is affected.  The statements within the loop are executed repeatedly, while control-variable is incremented or decremented from initial-value to final-value.  

In the TO form, final-value must be greater than or equal to initial-value to cause the loop to execute.

In the DOWNTO form, final-value must be less than or equal to initial-value.  

In the normal execution of a FOR loop, control-variable is initialized to initial-value.  Control-variable is then compared to final-value, and if it is greater than (using the TO form) or less than (using the DOWNTO form) final-value, control is passed to the statement following the ENDFOR statement.   Otherwise, control is passed to the statement or block within the FOR loop.  When control reaches the ENDFOR statement, control-variable is incremented or decremented and then compared with final-value.  Depending on the result of the comparison, the statement or block within the loop is executed again or the loop terminates.
 

Example

FOR #I = 1 TO 10
            FAC = FAC + #I
ENDFOR

The statement FAC = FAC + #I is executed 10 times.  The first time through the loop, the variable #I has the value of 1, the second time through it has the value 2, and so on.  For each value of #I from 1 to 10, the value of #I is added to FAC.