tr@thumper.UUCP (05/29/87)
[If this line had not been eaten,
According to _Advanced MS-DOS_ by Ray Duncan, DOS function C (hex)
resets the input buffer and then gets a character for input using one
of five DOS functions. They are 1, 6, 7, 8, and A (hex). I want to
flush the keyboard without getting input. The reason for this is that
the next thing my program does is call up a canned function that uses
keyboard input.
I am using Lattice C. Is there a standard way of doing this with C or
Assembler? I would not expect
fflush(stdin);
to work because fflush is said to be for output buffers.
Thank you for your attention. You people are great.
--
Tom Reingold
INTERNET: tr@bellcore.bellcore.com
UUCP: {seismo,ihnp4,ucbvax,decvax}!bellcore!tr
{ulysses,allegra,clyde,princeton}!bellcore!trdarrylo@hpsrlc.HP.COM (Darryl Okahata) (06/02/87)
In comp.sys.ibm.pc, tr@thumper.UUCP writes: > >According to _Advanced MS-DOS_ by Ray Duncan, DOS function C (hex) >resets the input buffer and then gets a character for input using one >of five DOS functions. They are 1, 6, 7, 8, and A (hex). I want to >flush the keyboard without getting input. The reason for this is that >the next thing my program does is call up a canned function that uses >keyboard input. > >I am using Lattice C. Is there a standard way of doing this with C or >Assembler? I would not expect > > fflush(stdin); > >to work because fflush is said to be for output buffers. > >Thank you for your attention. You people are great. > >-- >Tom Reingold >INTERNET: tr@bellcore.bellcore.com >UUCP: {seismo,ihnp4,ucbvax,decvax}!bellcore!tr > {ulysses,allegra,clyde,princeton}!bellcore!tr >---------- With assembler, you use two DOS functions (I don't remember the function numbers): one which checks to see if a keyboard character is available, and another to read a keyboard character. From here, it's simple (given in C pseudocode): while (character_available()) read_character(); /* throw read characters into the bit bucket */ I don't know of any *standard* way to do this. -- Darryl Okahata ucbvax!ucbcad!ames!hplabs!hpcea!hpsrla!darrylo <== best path hplabs!hpcea!hpsrla!darrylo <== alternative CompuServe: 75206,3074 Disclaimer: the above is the author's personal opinion and is not the opinion or policy of his employer or of the little green men that have been following him all day.
mjg@ecsvax.UUCP (06/02/87)
In article <747@thumper.UUCP>, tr@thumper.UUCP writes: > According to _Advanced MS-DOS_ by Ray Duncan, DOS function C (hex) > resets the input buffer and then gets a character for input using one > of five DOS functions. They are 1, 6, 7, 8, and A (hex). I want to > flush the keyboard without getting input. The reason for this is that > the next thing my program does is call up a canned function that uses > keyboard input. > Here is one way to clear the typahead buffer that I am using successfully in one of my programs. Since the buffer has been flushed there will not be anything there but I call function 06 anyway as you MUST specify one of the functions 1,6,7,8 or A anyway. By using 6 it just checks the buffer which is empty and returns immediately without waiting. If by some remote chance a key has been pressed in the split second etween flushing the buffer and returning then it will be discarded. by the 06 calls. ---------------------------------------------------- ; Clear typeahead buffer routine ; uses flush buffer call, which must specify ; a keyboard command to follow. This method uses ; the int 21h call # 06 which reads the keyboard ; but does not wait for a character ctahed proc near mov ah,0ch ;flush keyboard buffer mov al,06 ;function forces a read mov dl,0ffh ;int 21, 06 afterwards. int 21h jz nochar ; or al,al ;if extended char was typed jz nochar ;get rid if it by another mov al,6 ;read mov dl,0ffh int 21h nochar: ret ctahed endp ---------------------------------------------------- ......decvax!mcnc!ecsvax!mjg
bmarsh@cod.UUCP (06/02/87)
In article <747@thumper.UUCP>, tr@thumper.UUCP writes: > According to _Advanced MS-DOS_ by Ray Duncan, DOS function C (hex) > resets the input buffer and then gets a character for input using one > of five DOS functions. They are 1, 6, 7, 8, and A (hex). They always forget to add the fact that you can use this function with a 'function' of zero. This will flush the keyboard input buffer, then return without asking for a character, exactly as you wanted. > I am using Lattice C. Is there a standard way of doing this with C or > Assembler? bdos(0x0c, 0x00, 0x00); or mov ax,0c00h int 21h > Thank you for your attention. You people are great. Thanks. (blush ;-) > -- > Tom Reingold > INTERNET: tr@bellcore.bellcore.com > UUCP: {seismo,ihnp4,ucbvax,decvax}!bellcore!tr > {ulysses,allegra,clyde,princeton}!bellcore!tr --------- Bill Marsh, Naval Ocean Systems Center, San Diego, CA {arpa,mil}net: bmarsh@cod.nosc.mil uucp: {ihnp4,akgua,decvax,dcdwest,ucbvax}!sdcsvax!nosc!bmarsh "If everything seems to be coming your way, you're probably in the wrong lane."
markg@amd.UUCP (06/03/87)
In article <708@cod.UUCP> bmarsh@cod.UUCP (William C. Marsh) writes: >They always forget to add the fact that you can use this function with a >'function' of zero. This will flush the keyboard input buffer, then return >without asking for a character, exactly as you wanted. > This is a first in a long time. I finally got some useful information from this newsgroup. I didn't learn much about how to UNFORMATT a floppy or why I would like to make PC|MSDOS crash via =" ". Thank GOD someone out there has brains!! -- Mark Gorlinsky - AMD Processor Products Division/APPS SQA UUCP: {decwrl,ihnp4,allegra}!amd!markg AT&T: (408) 982-7811 DISCLAIMER: My opinions are mine, not my employers.
cjdb@sphinx.UUCP (06/03/87)
In article <4063@amd.UUCP> markg@amd.UUCP (Mark Gorlinsky) writes: >[...] >This is a first in a long time. I finally got some useful information >from this newsgroup. I didn't learn much about how to UNFORMATT a floppy or >why I would like to make PC|MSDOS crash via =" ". Thank GOD someone out there >has brains!! > We all have brains, and that's >" ", by the way. Here's how I flush the keyboard when I'm not busy freezing up the machine ( :-) ): mov ah,0 ; BIOS function to read char from kbd int 16h ; call BIOS AH contains the scan code, AL the character. Don't process = throw away. I'm not saying this is better than the other methods posted (after all, one is counselled to use DOS wherever one can), but simply different. -- Bitnet: lib.cb@uchicago.bitnet Internet: lib.cb@chip.uchicago.edu uucp: ..!ihnp4!gargoyle!sphinx!cjdb
markg@amd.UUCP (06/03/87)
In article <3320019@hpsrlc.HP.COM> darrylo@hpsrlc.HP.COM (Darryl Okahata) writes: >In comp.sys.ibm.pc, tr@thumper.UUCP writes: >> > With assembler, you use two DOS functions (I don't remember the >function numbers): one which checks to see if a keyboard character is >available, and another to read a keyboard character. From here, it's >simple (given in C pseudocode): > > while (character_available()) > read_character(); /* throw read characters into the > bit bucket */ > The shortest way (from the view point of your own program) is to use DOS Function 0Ch with AL=0. This function will clear the entire keyboard buffer and only requires two lines of assembly or one line of C code. examples: (assembly) mov ax,0C00h int 21h (C) bdos(0x0C, 0, 0); (Turbo C, MSC,or Lattice) -- Mark Gorlinsky - AMD Processor Products Division/APPS SQA UUCP: {decwrl,ihnp4,allegra}!amd!markg AT&T: (408) 982-7811 DISCLAIMER: My opinions are mine, not my employers.
platt@emory.UUCP (06/06/87)
In article <747@thumper.UUCP> tr@thumper.UUCP writes: > ...I want to flush the keyboard without getting input. >flush the keyboard without getting input. >I am using Lattice C. Is there a standard way of doing this with C or >Assembler? I would not expect > fflush(stdin); >to work because fflush is said to be for output buffers. Actually, I've found fflush(stdin) works quite well here. It's true that fflush is usually used for output, and isn't needed for UNIX C, but I've found that functions such as getchar() have a problem with the carriage return without flushing after getting only one character. Without the fflush(stdin) the next getchar() returns a '\n'. But then, I'm using MS C ver 4.0, but the routines are probably similarly quirky with Lattice C. Anyway, I've seen it work, and I've used it for the above problem. Hope it's a help, and I hope it works with lattice C. Dan