DOS ain't dead - 18 Bytes !!! Anyone can beat this? HEX16 for 8086

DOS386

13.04.2009, 10:20

18 Bytes !!! Anyone can beat this? HEX16 for 8086 (Developers)

Task: convert the value in DX (or some other register) into a 4-Bytes string representing the number in HEX using 8086 compatible instructions (no TSR this time, sorry :crying: )

Solution by King Udo (31 Bytes):

output_hex: ; On Entry: ; dx = 2 byte hex value ; On Exit: ; None mov cx,4 output_hex10: mov al,dh push cx mov cl,4 shr al,cl pop cx and al,0fh cmp al,09h ; greater 0-9? jg output_hex20 add al,30h jmp output_hex30 output_hex20: add al,37h output_hex30: ; call onecharal push cx mov cl,4 shl dx,cl pop cx loop output_hex10

My solution (18 Bytes):

use16 ; HEX16 output conversion, 8086 compatible ; Input in DX or AX | Trashes AX CX DX ; 9 instructions 18 Bytes vary bare input in DX ; 10 instructions 19 Bytes very bare input in AX ; 11 instructions 22 Bytes including call, input in AX ; 18 instructions 29 Bytes including call, full register preservation and RET push ax push cx push dx xchg dx, ax ; DX <- AX | Later peek the 4-bit groups from DX mov cx, 1028 ; "MOVNTQ CL, 4" + "MOVNTQ CH, 4" @@: mov al, dh ; AL <- DH | Move all 8 bits, only upper 4 useful shl dx, cl ; 8086 compatible shr al, cl ; 8086 compatible cmp al, 10 ; Now must be and is AL<=15 | Decimal "10" !!! sbb al, $69 ; Securely Bugged Backup das ; Digital Attack System | ASCII result in AL call onecharal ; Input in AL | Must preserve CX and DX, not AX dec ch ; & No LOO'p on CH jnz short @b ; & pope dx pope cx pope ax ret ;----

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This is a LOGITECH mouse driver, but some software expect here
the following string:*** This is Copyright 1983 Microsoft ***

ecm

Düsseldorf, Germany,
13.04.2009, 14:08

@ DOS386

18 Bytes! Anyone can beat this? - No

Post reply

My solution requires 34 bytes, but I think it's easier to understand than using das (or daa, see below).

disp_ax_hex: ; ax xchg al,ah call disp_al_hex ; display former ah xchg al,ah ; and fall trough for al disp_al_hex: ; al push cx mov cl,4 ror al,cl call disp_al_lownibble_hex ; display former high-nibble rol al,cl pop cx ; and fall trough for low-nibble disp_al_lownibble_hex: push ax ; save ax for call return and al,00001111b ; high nibble must be zero add al,'0' ; if number is 0-9, now it's the correct character cmp al,'9' jna .decimalnum ; if we get decimal number with this, ok --> add al,7 ; otherwise, add 7 and we are inside our alphabet .decimalnum: call disp_al pop ax retn

I think Henrik Haftmann's solution is good, too. It still requires 26 bytes. (Note that _ochr is actually the call to display the character in al, so it doesn't count. Note also that these macros aren't used as macros multiple times per program, they're used once, then they're called inside the program.)

macro _ochr ;Zeichenausgabe aus AL ochr: push ax dx mov dl,al DOS 2 pop dx ax ret endm macro _axhx ;Hexzahlausgabe, VR: AX,F axhx: xchg al,ah call ahex xchg al,ah ahex: push ax cx ;Werte erhalten mov cl,4 ;oberes Nibble auf Bit 3...0 shr al,cl ; schieben pop cx call ahex1 pop ax ahex1: and al,0fh add al,90h ;Hex -> ASCII daa adc al,40h daa _ochr endm

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l

DOS386

13.04.2009, 14:32

@ ecm

18 Bytes! Anyone can beat this? - No DAS

Post reply

> easier to understand than using das

Just replace (5 Bytes):

cmp al, 10 ; Now must be and is AL<=15 | Decimal "10" !!! sbb al, $69 ; Securely Bugged Backup das ; Digital Attack System | ASCII result in AL

by (8 Bytes):

cmp al, 10 jb short heh add al, 7 heh: add al, 48

So my code grows to 21 Bytes. I have no idea how DAS works but it does :clap:

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This is a LOGITECH mouse driver, but some software expect here
the following string:*** This is Copyright 1983 Microsoft ***

Berlin, Germany,
13.04.2009, 16:13

@ DOS386

18 Bytes! Anyone can beat this? - No DAS

Post reply

> So my code grows to 21 Bytes. I have no idea how DAS works but it
> does :clap:

http://www.df.lth.se/%7Ejohn_e/gems/gem003a.html

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Forum admin

mht

Wroclaw, Poland,
13.04.2009, 16:04

@ DOS386

18 Bytes !!! Anyone can beat this? HEX16 for 8086

Post reply

You can still improve register usage. Use rotations on one register instead of shifts on two (4 rotations by 4 bits = no-op).
But anyway, what are you trying to show?
1. "Work-In-Progress version" certainly may contain some (possibly even unused) debug code and there is nothing wrong with it.
2. Optimizing such pieces of code is wasting time, it will be surely removed in a "production" version.
3. You can find source files where unclear tricks (like the old DAS one) are commented and explained, better cut-and-paste from there, instead of introducing additional noise.

DOS386

18.05.2009, 05:54
(edited by DOS386, 18.05.2009, 06:09)

@ mht

18 Bytes !!! Anyone can beat this? HEX16 for 8086 | ROL

Post reply

rr wrote:

> http://www.df.lth.se/%7Ejohn_e/gems/gem003a.html

:-)

mht wrote:

> You can still improve register usage. Use rotations on one
> register instead of shifts on two (4 rotations by 4 bits = no-op).

Thanks :-) You can't beat the 18 Bytes this way but indeed improve the "useful" variant :-)

> better cut-and-paste from there, instead of introducing additional
> noise

Welcome back to NOiSe ain't dead - the great C&P forum :confused:

use16 ; HEX16 output conversion, 8086 compatible ; Input in AX | Trashes CX only !!! ; 9 instructions 18 Bytes vary bare, input in DX, trashes AX ; 10 instructions 18 Bytes very bare, input in AX, uses stack ; 10 instructions 19 Bytes very bare, input in AX, trashes DX, no stack ; 11 instructions 21 Bytes including call, input in AX, uses stack ; 14 instructions 24 Bytes including call, full register preservation and RET hex16: push cx mov cx, 1028 ; "MOVNTQ CL, 4" + "MOVNTQ CH, 4" h16l: rol ax, cl ; 8086 compatible, after 4 ROL's original back ; rol dx, cl ; 8086 compatible, after 4 ROL's original back ; mov al, dl ; AL <- DL , transfer 8 bits, only 4 are useful push ax ; mov dx, ax ; Now both DX and AX are equal, XCHG not good and al, $0F cmp al, 10 ; Now must be and is AL<=15 | Decimal "10" !!! sbb al, $69 ; Securely Bugged Backup das ; Digital Attack System | ASCII result in AL call onecharal ; Input in AL | Must preserve CX (+ DX or AX) pope ax ; xchg dx, ax ; Restore trashed AX from DX, but now DX trash dec ch ; & No LOO'p on CH jnz short h16l ; & pope cx ret ;---- ; Avoiding cryptic "DAS" (also preceding SBB, OTOH keep CMP) costs 3 Bytes: cmp al, 10 jb short @f ; OK, 0 ... 9 add al, 7 ; Fix for A ... F @@: add al, 48

---
This is a LOGITECH mouse driver, but some software expect here
the following string:*** This is Copyright 1983 Microsoft ***