DOS ain't dead

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 ) 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         ;----

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

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 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 ***

> So my code grows to 21 Bytes. I have no idea how DAS works but it > does http://www.df.lth.se/%7Ejohn_e/gems/gem003a.html

---
Forum admin

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.

> 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

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

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

---
l