;-----------------------------QBASIC
;CALL ABSOLUTE(b%, b$, bin)
; input  : b%   : a value - ex: 157
; output : b$   : a string with length = 16, filled with spaces
;                 for the computed binary string - ex: "100011101"
; code   : bin  : where this code is loaded with BLOAD
;-----------------------------MASM header
        ASSUME CS:CODE
CODE    SEGMENT
        ORG 0           ;this is a binary file
;-----------------------------BSAVE/BLOAD header
head:   db  0FDh        ;BSAVE/BLOAD ID
        dw  9999h       ;segment - not used - any value is ok
        dw  9999h       ;offset  - not used - any value is ok
        dw  Last-First  ;computed size of code
;-----------------------------Code
First:
        push bp         ;standard entry
        mov bp,sp       ;[bp+0] : old bp
                        ;[bp+2] : QBASIC return offset
                        ;[bp+4] : QBASIC return segment
                        ;[bp+6] : offset b$ descriptor
                        ;[bp+8] : offset b%

        mov bx, [bp+6]  ;b$ descriptor
        mov si, [bx+2]  ;b$ offset
        add si, 16      ;point after last char

        mov bx, [bp+8]  ;b% offset
        mov ax, [bx]    ;b%

do:     dec si          ;point to previous char
        mov cx, ax      ;b%
        and cx, 1       ;test last bit of b%
        jz zero
        mov byte ptr [si], '1'
        jmp next

zero:   mov byte ptr [si], '0'
next:   shr ax, 1       ;shift all bits in c% 1 pos right

        jnz do          ;repeat if c% is not zero

fin:    pop bp          ;standard exit
        retf 4          ;far return - clean up two parameters
;-----------------------------
Last:
CODE    ENDS
        END head

;-----------------------------QBASIC:
;CALL ABSOLUTE(b$, b%, VARPTR(bins))
; input  : b$   : a binary string - ex: "10011101"
; output : b%   : the returned value of bs$ - ex: 157
; code   : bins : a variable used as container for the code loaded by BLOAD
;-----------------------------MASM header:
	ASSUME CS:CODE
CODE	SEGMENT
	ORG 0 		;this is a binary file
;-----------------------------BSAVE/BLOAD header:
head:	db 0FDh 	;BSAVE/BLOAD ID
	dw 9000h 	;segment - not used - any value is ok
	dw 0000h 	;offset  - not used - any value is ok
	dw Stop-Start 	;computed size of code
;-----------------------------Code:
Start:	push bp 	;standard QBASIC entry
	mov bp,sp 	;[bp+0] : old bp
			;[bp+2] : QBASIC return segment
			;[bp+4] : QBASIC return offset
			;[bp+6] : offset b% (last parameter)
			;[bp+8] : offset b$ descriptor

	mov bx,[bp+8] 	;b$ descriptor
	mov cx,[bx] 	;b$ length
	mov si,[bx+2] 	;b$ offset
	add si,cx 	;initialize bit pointer: last+1
	mov ax,0 	;initial b% value
	mov bx,1 	;initial bit value
	inc cx 

  
do: 	dec cx		;count bits
	jz return	;stop when done
	dec si		;next bit - from last to first
	mov dl,[si] 	;read bit
	sub dl,48	;convert from ascii to value (asc("0")=48)
	jz loop		;if "0": skip
	add ax,bx 	;if "1": add bit value to b% (= ax)
loop:	add bx,bx 	;compute next bit value (* 2)
	jmp short do

return:	mov si,[bp+6]	;b% offset
	mov [si],ax 	;return final b% value

	pop bp 		;standard QBASIC exit
	retf 4 		;far return - clean up 2 parameters: 
			;bs$ and b% (2 bytes each)
Stop:

;-----------------------------MASM end:
CODE 	ENDS
	END head	;first code - placed at ORG 0