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8085 Debugging help

Discussion in 'Assembly Language Programming (ALP) Forum' started by jonross, Jan 6, 2015.

  1. jonross

    jonross New Member

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    Hi, I was wondering if anyone could help me with debugging this program? It's not printing out the way I expected it to, and I could use another set of eyes to help me figure out what's wrong with it. It's supposed to print out 3 vertical lines of X's of a length determined by the user, but isn't printing out the lines correctly.

    Thanks!

    Code:
       bdos      equ    5            ; CP/M function call address
       boot      equ    0            ; address to get back to CP/M
       conin     equ    1            ; keyboard read function number
       conout    equ    2            ; console output function number
       sprint    equ    9            ; string print function number
       cr        equ    0Dh          ; value of ASCII code of <CR>
       lf        equ    0Ah          ; value of ASCII code of line feed
    
    ;
    	org 0100h	
    	lxi sp,sp0	;init stack
    	mvi c, sprint
    	lxi d, title	;calls first part of title at title
    	call bdos
    	mvi c, sprint
    	lxi d, title2	;calls second part of title
    	call bdos
    	call lines
    	call print
    	mvi c, sprint
    	lxi d,endgraph
    	call bdos
    	lxi d,endmess
    	call bdos
    	jmp boot
    
    
    
    
    
    ;lines subroutine
    lines:	mvi c, sprint
    	lxi d, line1	;prompts for 1st length
    	call bdos							;1=b
    	mvi c, conin
    	call bdos
    	mov b,a		;moves 1st length into b
    	
    	mvi c, sprint
    	lxi d, line2	;prompts for 2nd length
    	call bdos
    	mvi c, conin							;2=d
    	call bdos
    	mov d,a		;moves 2nd length into d
    	push d
    
    	mvi c, sprint
    	lxi d, line3	;prompts for 3rd length
    	call bdos
    	mvi c, conin							;3=h
    	call bdos
    	mov h,a		;moves 3rd length into h
    	pop d
    	ret
    
    
    
    ;print subroutine
    print:	mvi c,conout
    	push d		;keeps d from being overwritten
    	lxi d,enter	;puts in an enter
    	call bdos
    	pop d	
    	mov a,b		;1st len to a
    	cmp d		;1st-2nd
    	jm sec		;2nd>=1st
    	jz sec
    	cmp h		;1st-3rd
    	jm threeh	;3rd>=1st>2nd, otherwise is 1st>2nd>3rd
    	jz threeh
    	jmp oneh
    
    sec:	mov a,d
    	cmp h		;2nd-3rd
    	jm threeh	;3rd>=2nd>=1st, otherwise 2nd is highest
    	jz threeh
    	jmp twoh
    
    oneh:	mov a,b
    reponeh:
    	cpi 0
    	rz		;ends prog once gets to end of 1s
    	push d		;keeps d from being overwritten
    	lxi d,xchar	;puts in an x
    	call bdos	
    	mvi c,conout
    	lxi d,fourspace	;puts in 4 spaces
    	call bdos
    	pop d	
    	call bdos
    	cmp d		;1st-2nd
    	jp twospace	;puts in space
    	push d		;keeps d from being overwritten
    	lxi d,xchar	;puts in an x
    	call bdos	
    two:	lxi d,fourspace	;puts in 4 spaces
    	call bdos	
    	call bdos
    	cmp h		;1st-3rd
    	jp threespace	;puts in space
    	lxi d,xchar	;puts in an x
    	call bdos
    three:	sui 1		;decriments counter
    	lxi d,enter	;puts in an enter
    	call bdos
    	pop d	
    	jmp reponeh
    
    twospace:
    	push d		;keeps d from being overwritten
    	lxi d,space	;puts in a space
    	call bdos	
    	jmp two
    
    threespace:
    	lxi d,space	;puts in a space
    	call bdos	
    	jmp three	
    
    
    twoh:	mov a,d
    reptwoh:
    	cpi 0
    	rz
    	cmp b		;2nd-1st	
    	jp twohonespace	;puts in space
    	lxi d,xchar	;puts in an x
    	call bdos	
    twohone:
    	lxi d,fourspace	;puts in 4 spaces
    	call bdos
    	lxi d,xchar	;puts in an x
    	call bdos
    	lxi d,fourspace	;puts in 4 spaces
    	call bdos
    	call bdos
    	cmp h		;2nd-3rd
    	jp twohthreespace	;puts in space
    	lxi d,xchar	;puts in an x
    	call bdos
    twohthree:
    	sui 1		;decriments counter
    	lxi d,enter	;puts in an enter
    	call bdos
    	jmp reptwoh
    
    twohonespace:
    	lxi d,space	;puts in a space
    	call bdos
    	jmp twohone
    
    twohthreespace:	
    	lxi d,space	;puts in a space
    	call bdos
    	jmp twohthree
    
    
    threeh:	mov a, h
    repthreeh:
    	cpi 0
    	rz
    	cmp b		;3rd-1st
    	jp threehonespace	;puts in space
    	push d		;keeps d from being overwritten
    	lxi d,xchar	;puts in an x
    	call bdos
    threehone:
    	lxi d,fourspace	;puts in 4 spaces
    	call bdos
    	pop d	
    	call bdos
    	cmp d		;3rd-2nd
    	jp threehtwospace
    	push d		;keeps d from being overwritten
    	lxi d,xchar	;puts in an x
    	call bdos	
    threehtwo:
    	lxi d,fourspace	;puts in 4 spaces
    	call bdos
    	lxi d,xchar	;puts in an x
    	call bdos	
    	sui 1		;decriments counter
    	lxi d,enter	;puts in an enter
    	call bdos
    	pop d	
    	jmp repthreeh
    
    threehonespace:
    	lxi d,space	;puts in a space
    	call bdos	
    	jmp threehone
    
    threehtwospace:
    	push d		;keeps d from being overwritten
    	lxi d,space	;puts in a space
    	call bdos	
    	jmp threehtwo	
    	
    
    
    
    
    title: db 'Three Lines$'
    title2: db lf,cr, 'I will print three lines of given lengths$'
    line1: db lf,cr,'Length of first line: $'
    line2: db lf,cr,'Length of second line: $'
    line3: db lf,cr,'Length of third line: $'
    xchar: db 'X    $'
    enter: db lf,cr, '$'
    fourspace: db '    $'
    space: db '     $'
    endgraph: db lf,cr, '1    2    3$'
    endmess: db lf,cr,'Thank you for using the Three Lines program$'
    
    
    	ds 20		;reserve for stack
       	sp0 equ $	;stack pointer address
    	end
     
  2. xpi0t0s

    xpi0t0s Mentor

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    Can you give a couple of examples of the input you give and the output you got? It's easier to see where a program is going wrong with some output.
     
  3. jonross

    jonross New Member

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    Right now if I put in something like
    Code:
    Length of first line: 6
    Length of second line: 4
    Length of third line: 2
    I just get

    Code:
    1    2    3
    Thank you for using the Three Lines Program
    as output. But it should be giving me something more like

    Code:
    X        
    X        
    X    X
    X    X
    X    X    X
    X    X    X
    1    2    3
    Thank you for using the Three Lines Program
    I can't quite figure out where the program stops working, as the registers have the proper numbers in them.
     
  4. xpi0t0s

    xpi0t0s Mentor

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    Could you show the complete unedited output please?
     

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