If reading from a character device (such as the standard input) in cooked mode, at most one line of input will be read (i.e., up to a carriage return character or the specified length, whichever comes first).Given a valid file handle from a previous open or create operation, a buffer address, and a length in bytes, transfers data at the current file-pointer position from the file into the buffer and then updates the file pointer position.
Call with:
AH = 3FH
BX = handle
CX = number of bytes to read
DS:DX = segment:offset of buffer
Returns:
If function successful
Carry flag = clear
AX = bytes transferred
If function unsuccessful
Carry flag = set
AX = error code
Notes:
If reading from a character device (such as the standard input) in cooked mode, at most one line of input will be read (i.e., up to a carriage return character or the specified length, whichever comes first).
If the carry flag is returned clear but AX = 0, then the file pointer was already at end of file when the program requested the read.
If the carry flag is returned clear but AX < CX, then a partial record was read at end of file or there is an error.
[3.0+] If the program is running on a network, the user must have Read access rights to the directory and file.
Example:
Using the file handle from a previous open or create operation, read 1024 bytes at the current file pointer into the buffer named buff.
buff db 1024 dup (?) ; buffer for read
fhandle dw ? ; contains file handle
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mov ah,3fh ; function number
mov dx,seg buff ; buffer address
mov ds,dx
mov dx,offset buff
mov bx,fhandle ; file handle
mov cx,1024 ; length to read
int 21h ; transfer to MS-DOS
jc error ; jump, read failed
cmp ax,cx ; check length of read
jl done ; jump, end of file
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