popram - BASIC Commands

Name:

popram

Syntax:

POPRAM

Description:

Restore the contents of RAM 0-15 (variables b0-b15) from the 4 level 'RAM stack'.

To reuse variables within a macro/sub-procedure it can be useful to 'free up' variables so that they can be reused as temporary variables within the macro. The pushram command pushs the contents of b0-b15 onto the ram stack so that they can then be reused for other purposes. The popram command then restores the original values at the end of the macro.

The 4-level stack used for pushram and popram is separate to the stack used for push and pop commands.

Applies To:

20X2, 28X2, 40X2

See Also:

Related Create:

Protecting variable values

Before calling a subroutine a 'pushram' is executed so variables can be restored, if the subroutine uses those variables and alters their values. After the subroutine completes a 'popram' must be executed to restore the original variable values as they were previously.

Code Example:

main:	for b1 = 1 to 5
	  sertxd( "Before gosub, b1=", #b1, cr, lf )
	  pushram
	  gosub mysub
	  popram
	  sertxd( "After gosub, b1=", #b1, cr, lf, cr, lf )
	next
	end
	
mysub:	b1 = 99	
	sertxd( "   Inside mysub, b1=", #b1, cr, lf )
	return

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Use within subroutine

On entry into the subroutine a 'pushram' is used to allow re-use of variables within the routine. At the end of the routine, before any return, a 'popram' must be executed to restore the original variable values as they were outside the subroutine.

Code Example:

main:	for b1 = 1 to 5
	  sertxd( "Before gosub, b1=", #b1, cr, lf )
	  gosub mysub
	  sertxd( "After gosub, b1=", #b1, cr, lf, cr, lf )
	next
	end
	
mysub:	pushram
	b1 = 99	
	sertxd( "   Inside mysub, b1=", #b1, cr, lf )
	popram
	return

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