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From: ForthNet@willett.pgh.pa.us (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Forth vs C
Message-ID: <2035.UUL1.3#5129@willett.pgh.pa.us>
Date: 2 Dec 90 16:59:32 GMT
Organization: String, Scotch tape, and Paperclips.  (in Pgh, PA)
Lines: 31

Category 2,  Topic 14
Message 4         Sun Dec 02, 1990
NMORGENSTERN                 at 11:45 EST
 
How to determine if a file exists without the overhead of opening it. It
 calls function 43H which gets the attribute flag using the general-duty  DOS
call HDOS1.

: NonExistent? ( h -- f)  \ 0= ok, 2= file not found, 3= path not found >nam 0
swap 17152               \ 4300 hex gets file attribute hdos1               \
atr 0 | code 1 0= if drop 0 then  ;    \ We don't really want attribute

I am looking for a better name for this word.

I was all wrong about the Abort Retry etc message. I mistakenly thought  that
it did not occur when you called file functions directly via int 21H.
 You can bypass this if you are expert enough. Int 24H returns the address
 of the Critical Error Handler routine. It is set to the Abort Retry etc 
routine. I am reminded of the riddle: How do porcupines have sex? Answer:
 Carefullly

However you can test for such problems as door open, etc. by calling INT
 25H which is absolute disk read. It attempts to read 1 sector into PAD,
 and returns an error flag. Drive is 0 for A: 1 for B: etc. Flag is 0 if  ok.
2 is drive not ready. See DOS manual for other codes.

code DriveError? ( drive -- f) pop ax  xor ah, ah  mov cx, # 1  xor dx, dx mov
bx, # pad  int 37  xor ah, ah  1push end-code.
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