For...Next...Step

Syntax

For Variable = Startcount to Endcount [ Step { Stepval } ] {code body} Next

Overview

The For…Next loop is used to execute a statement, or series of statements a predetermined amount of times.

Parameters

Variable refers to an index variable used for the sake of the loop. This index variable can itself be used in the code body but beware of altering its value within the loop as this can cause many problems. Startcount is the start number of the loop, which will initially be assigned to the variable. This does not have to be an actual number - it could be the contents of another variable. Endcount is the number on which the loop will finish. This does not have to be an actual number, it could be the contents of another variable, or an expression. Stepval is an optional constant or variable by which the variable increases or decreases with each trip through the For-Next loop. If Startcount is larger than Endcount, then a minus sign must precede Stepval.

Example 1

' Display in decimal, all the values of MyWord within an upward loop
  Device = 24FJ64GA002             ' Select the device to compile for
  Declare Xtal = 16
  Declare Hserial_Baud = 9600       ' USART1 Baud rate
  Declare Hrsout1_Pin = PORTB.14    ' Select the pin for TX with USART1

  Dim MyWord as Word

  RPOR7 = 3                         ' Make PPS Pin RP14 U1TX
  For MyWord = 0 to 2000 Step 2   ' Perform an upward loop
     Hrsout Dec MyWord, 13           ' Display the value of MyWord
  Next                              ' Close the loop

Example 2

' Display in decimal, all the values of MyWord within a downward loop
  Device = 24FJ64GA002             ' Select the device to compile for
  Declare Xtal = 16
  Declare Hserial_Baud = 9600       ' USART1 Baud rate
  Declare Hrsout1_Pin = PORTB.14    ' Select the pin for TX with USART1

  Dim MyWord as Word

  RPOR7 = 3                         ' Make PPS Pin RP14 U1TX
  For MyWord = 2000 to 0 Step -2   ' Perform a downward loop
     Hrsout Dec MyWord, 13           ' Display the value of MyWord
   Next                              ' Close the loop

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Example 3

' Display in decimal, all the values of MyDword within a downward loop
  Device = 24FJ64GA002             ' Select the device to compile for
  Declare Xtal = 16
  Declare Hserial_Baud = 9600       ' USART1 Baud rate
  Declare Hrsout1_Pin = PORTB.14    ' Select the pin for TX with USART1

  Dim MyDword as Dword

  RPOR7 = 3                         ' Make PPS Pin RP14 U1TX
   For MyDword = 200000 to 0 Step -200 ' Perform a downward loop
     Hrsout Dec MyDword, 13           ' Display the value of MyDword
   Next                                ' Close the loop

Example 4

' Display all of MyWord1 using expressions as parts of the For-Next
  Device = 24FJ64GA002             ' Select the device to compile for
  Declare Xtal = 16
  Declare Hserial_Baud = 9600       ' USART1 Baud rate
  Declare Hrsout1_Pin = PORTB.14    ' Select the pin for TX with USART1

  Dim MyWord1 as Word
   Dim MyWord2 as Word

  RPOR7 = 3                           ' Make PPS Pin RP14 U1TX
  MyWord2 = 1000

  For MyWord1= MyWord2 + 10 to MyWord2 + 1000   ' Perform a loop
     Hrsout Dec MyWord1, 13                  ' Display the value of MyWord1
   Next                                       ' Close the loop

Notes.

It may have been noticed from the above examples, that no variable is present after the Next command. A variable name after Next is purely optional.

For-Next loops may be nested as deeply as the code memory on the microcontroller will allow. To break out of a loop you may use the GoTo command without any ill effects, which is exactly what the Break command does: -

For MyByte = 0 to 20                  ' Create a loop of 21
  If MyByte = 10 Then GoTo BreakOut   ' Break out of loop when MyByte is 10
Next                                   ' Close the loop

BreakOut:

See also : While...Wend, Repeat...Until.

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