Help with this little program.
in [ASM]
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From: carlos on 25 Nov 2009 21:17 Hello, I'm trying to make a little program that do the following: Check if a key was pressed. If so, return the ascii value of the key. Otherwise, returns 0. I made this code, but I'm can't capturing the ascii value of the arrows. org 100h mov ah, 11h int 16h je pre_quit mov ah,8h int 21h cmp al,0 ; if not extended key jnz quit int 21h jmp quit pre_quit: mov al,0 quit: mov ah,4ch int 21h
From: Rod Pemberton on 25 Nov 2009 22:24 "carlos" <cmontiers(a)gmail.com> wrote in message news:77a6ea74-9e1e-4144-bcd4-5a074aad2bc4(a)m3g2000yqf.googlegroups.com... > Hello, I'm trying to make a little program that do the following: > > Check if a key was pressed. If so, return the ascii value of the key. > Otherwise, returns 0. > > I made this code, but I'm can't capturing the ascii value of the > arrows. > > org 100h > > mov ah, 11h > int 16h > je pre_quit > Those lines seems to have no effect on my machine. So, I commented them out: ; mov ah, 11h ; int 16h ; je pre_quit > mov ah,8h After trying to figure out why your code didn't work for a while, I realized that you probably confused ah=8h with ah=6h. It seems that ah=8h doesn't check for extended keys. I think what you want is: kbwait: mov ah,6h mov dl,0ffh ; needed to select input > int 21h It seems you are missing a wait loop. The function returns ZF set for no key available. It sets AL=0, if not an extended key. But, you must wait until a key is available (ZF clear) to check for AL=0... So: int21h jz kbwait ; wait for key > cmp al,0 ; if not extended key > jnz quit > int 21h > jmp quit > > pre_quit: > mov al,0 > quit: > mov ah,4ch > int 21h > In total, I get this: org 100h ; mov ah, 11h ; int 16h ; je pre_quit kbdwait: ; mov ah,8h mov ah,6h ; read w/extended mov dl,0ffh ; input int 21h jz kbdwait ; wait for key cmp al,0 ; if not extended key jnz quit int 21h jmp quit pre_quit: mov al,0 quit: mov ah,4ch int 21h HTH, Rod Pemberton PS. Threw on comp.os.msdos.programmer in case someone there knows how to do it with ah=8h, or has a better method.
From: Frank Kotler on 26 Nov 2009 07:28 carlos wrote: > Hello, I'm trying to make a little program that do the following: > > Check if a key was pressed. If so, return the ascii value of the key. > Otherwise, returns 0. > > I made this code, but I'm can't capturing the ascii value of the > arrows. I don't think arrow keys... or function keys, "editing keys" (home, end, etc.) actually *have* an "ascii code" (it's a "bios scan code", which looks the same). Been a while since I've done this, so I may misremember (my current install of dosemu is gefukt, and I don't feel like rebooting right now... I may have to...) > org 100h > > mov ah, 11h > int 16h > je pre_quit Rod says this does nothing on his machine. As I remember it, this should "check for" (not remove from keyboard buffer) a key. It should return immediately, with the zero-flag set if no key is available... so your program would end before it's begun! I must misremember this... One way to get "extended" keys is... mov ah, 10h int 16h cmp al, 0 jnz not_extended cmp ah, 48h je up_arrow cmp ah, 50h je down_arrow ; etc... not_extended: ; it's a "regular" key Note that we check ah, if al is zero. I'm pretty sure I remember this correctly... > mov ah,8h > int 21h > cmp al,0 ; if not extended key > jnz quit > int 21h > jmp quit But I thought I remembered that this should work, too - if it returns zero in al, call it again to get the "extended" key (in al). You *might* have to reload ah with 8 before the second int 21h. I don't think you should have to, but... easy to check, anyway. :) > pre_quit: > mov al,0 > quit: > mov ah,4ch > int 21h As I recall, if you do get the "extended key" on the second call, it'll look like 'M', 'H', 'P', ??? So you may not be able to distinguish the return value from a "regular" key. You might want to return 0FFh or something if it's an extended key... depending on what you intend to do with this. Rod's idea of using ah=6 (instead of 1, 7, or 8) may work out better for you, but I think int 16h is easier (just check ah, instead of calling it again). Your description of the program indicates that you want to return zero if no key is pressed. Generally, there won't be one - unless you're a *really* fast typist (or do myprog<sometext). Is this really what you want? Best, Frank
From: Alex Russell on 26 Nov 2009 11:35 Rod Pemberton wrote: > "carlos" <cmontiers(a)gmail.com> wrote in message > news:77a6ea74-9e1e-4144-bcd4-5a074aad2bc4(a)m3g2000yqf.googlegroups.com... >> Hello, I'm trying to make a little program that do the following: >> >> Check if a key was pressed. If so, return the ascii value of the key. >> Otherwise, returns 0. >> >> I made this code, but I'm can't capturing the ascii value of the >> arrows. >> >> org 100h >> >> mov ah, 11h >> int 16h >> je pre_quit >> > > Those lines seems to have no effect on my machine. So, I commented them > out: > > ; mov ah, 11h > ; int 16h > ; je pre_quit > >> mov ah,8h > > After trying to figure out why your code didn't work for a while, I realized > that you probably confused ah=8h with ah=6h. It seems that ah=8h doesn't > check for extended keys. I think what you want is: > > kbwait: > mov ah,6h > mov dl,0ffh ; needed to select input > >> int 21h > > It seems you are missing a wait loop. The function returns ZF set for no > key available. It sets AL=0, if not an extended key. But, you must wait > until a key is available (ZF clear) to check for AL=0... So: > > int21h > jz kbwait ; wait for key > >> cmp al,0 ; if not extended key >> jnz quit >> int 21h >> jmp quit >> >> pre_quit: >> mov al,0 >> quit: >> mov ah,4ch >> int 21h >> > > In total, I get this: > > org 100h > > ; mov ah, 11h > ; int 16h > ; je pre_quit > > kbdwait: > ; mov ah,8h > mov ah,6h ; read w/extended > mov dl,0ffh ; input > int 21h > jz kbdwait ; wait for key > cmp al,0 ; if not extended key > jnz quit > int 21h > jmp quit > > pre_quit: > mov al,0 > quit: > mov ah,4ch > int 21h > > HTH, > > > Rod Pemberton > PS. Threw on comp.os.msdos.programmer in case someone there knows how to do > it with ah=8h, or has a better method. > > According to my docs the jz kbdwait should not be required as int 21 func 08h is supposed to wait for the next key press or return the last key pressed. My dos machine is lent out so I can't test. The cmp al, 0 is required to check for extended keys. int 16h, func 00h also waits. This func returns scan codes in ah and ascii in al. al will be zero if a non-ascii key was pressed. This func doesn't require a second call to get the extended keys int21 and int16 both have funcs to check for a key being ready to prevent waits. Alex
From: s_dubrovich on 27 Nov 2009 22:43
On Nov 26, 6:28 am, Frank Kotler <fbkot...(a)myfairpoint.net> wrote: > carlos wrote: > > Hello, I'm trying to make a little program that do the following: > > > Check if a key was pressed. If so, return the ascii value of the key. > > Otherwise, returns 0. > > > I made this code, but I'm can't capturing the ascii value of the > > arrows. > > I don't think arrow keys... or function keys, "editing keys" (home, end, > etc.) actually *have* an "ascii code" (it's a "bios scan code", which > looks the same). Been a while since I've done this, so I may misremember > (my current install of dosemu is gefukt, and I don't feel like rebooting > right now... I may have to...) > Yeah, F11, F12, ScrollLock, Pause|Break, PrintScreen|SysRq, don't return on an AH`0, Int 16h call, they're ignored. The arrow keys, F1..F10, home, end, delete, pgup, pgdn and insert do return unique AH values (scan codes) but no ascii codes in AL, for example... Here's the main loop of my program.. ;;--------------------------------------------------------60 [SECTION .cseg vstart=0100h] ;; for .com Key_Scan: mov ax, 0000h ;; waits for keypress Int 16h ;; ZF is none awaits. ;; jz Key_Scan_Lp ;; .else. AH`scan code, AL`ascii chr ;; -= ck Xit chr; Q, q =- cmp ax, 1071h ;; q je Key_Scan_Xit cmp ax, 1051h ;; Q je Key_Scan_Xit ;; -= .else. conout AX =- call conout_AX nop nop ;; space for trap nop Key_Scan_Lp: jmp Key_Scan Key_Scan_Xit: call conout_AX ;; emit Q,q vals mov ah, 0 ;; pause for keypress.. int 16h int 19h ;; done ;;--------------------------------------------------------60 ;; S U B R O U T I N E S ;;--------------------------------------------------------60 My notes say Function 11h is a keyboard Check function, which does not remove the word from the keyboard buffer, you still need to 'remove' it by a 'read' Function 0h. I dunno, this might require experimentation. There were 3 keyboard base types. PC, XT, and AT class. For example: up arrow is AX=4800h, F10 is AX=4400h,'a' is AX=1E61h, shift+'a' is AX=1E41h (A). -on this Dell I'm banging on.. hth. Steve > > org 100h > > > mov ah, 11h > > int 16h > > je pre_quit > > Rod says this does nothing on his machine. As I remember it, this should > "check for" (not remove from keyboard buffer) a key. It should return > immediately, with the zero-flag set if no key is available... so your > program would end before it's begun! I must misremember this... > Yeah, _Check Keyboard_ > > Rod's idea of using ah=6 (instead of 1, 7, or 8) may work out better for > you, but I think int 16h is easier (just check ah, instead of calling it > again). > > Your description of the program indicates that you want to return zero > if no key is pressed. Generally, there won't be one - unless you're a > *really* fast typist (or do myprog<sometext). Is this really what you want? > > Best, > Frank |