Category: DOS-based task switchers/multitaskers

INT 12 - Back&Forth v1.62+ - API

	BX = function
	    00h installation check
		Return: AX = 0001h installed
			     else  not loaded
	    01h (reserved)
	    02h build program ID list (shareware Back&Forth)
		ES:DI -> buffer of at least 100 bytes, to be filled with words
		Return: AX = number of programs defined
			ES:DI buffer filled with AX words
	    02h get memory statistics (Back&Forth Professional)
		Return: AX = available swap memory, KBytes
			BX = maximum task size, KBytes
			DX = fixed overhead per task, excluding video/macro
	    03h switch to specified task (task need not be open yet)
		DX = two-letter program ID
		Return: AX = status
			    0000h if task undefined
			    0001h task switch will occur when safe
	    04h (reserved)
	    05h (reserved)
	    06h get version (documented only for Back&Forth Professional)
		Return: AX = version * 100 (v1.71 = 00ABh)
	    07h spawn program (Back&Forth Professional only???)
		ES:DI -> BF_SPAWN record (see #00232)
		Return: AX = status
			    0000h if no task handles free
			    0001h spawn will occur when safe
	    08h get open tasks (documented only for Back&Forth Professional)
		ES:DI -> task info buffer (see #00231,#00233)
		Return: AX = number of open tasks (max 20)
		Note:	the supplied buffer must be large enough to hold 21
			  task entries
	    09h (reserved)
	    ---Back&Forth Professional---
	    0Ah get active clipboard filename
		Return: DX:AX -> ASCIZ clipboard filename
	    0Bh get active task number
		AX = active task number (00h-13h)
		BX = number of tasks allocated
		DX = maximum number of tasks
	    0Ch (reserved)
	    0Dh (reserved)
	    0Eh (reserved)
	    0Fh stuff string into keyboard buffer
		ES:DI -> ASCIZ string to be stuffed
		Return: nothing
	    10h check if in graphics mode
		Return: AX = state
			    0000h color text mode
			    0004h mono text mode
			    FFFFh graphics mode
	    11h get Back&Forth Professional user number
		Return: AX = user number (0000h-00FFh)
	    12h switch task by task number
		DX = task number
		Return: AX = status
			    0000h attempted to switch to active task
			    0001h task switch will occur when safe
			    FFFFh invalid task number
	    13h delete (kill) task
		DX = task number
		Return: AX = status
			    0000h attempted to delete the active task
			    0001h successfully deleted
			    FFFFh invalid task number
		Note:	the active task number will change if the deleted task
			  was lower in the task list than the active task
	    14h get next available task handle
		Return:	AX = next available task handle
			    FFFFh if task table is full
Program: Back & Forth is a task switcher by Progressive Solutions, Inc.
SeeAlso: INT 11/AX=FFFEh
Index:	installation check;BACK&FORTH