AH=3FH - 8086 INT 21H

AH = 3Fh - "READ" - READ FROM FILE OR DEVICE
Entry:
BX = file handle
CX = number of bytes to read
DS:DX -> buffer for data
Return:
CF clear if successful - AX = number of bytes actually read (0 if at EOF before call)
CF set on error AX = error code (05h,06h)
Notes:
data is read beginning at current file position, and the file position is updated after a successful read
the returned AX may be smaller than the request in CX if a partial read occurred
if reading from CON, read stops at first CR

Syntax

MOV AH,3FH
INT 21H

Example

MOV AH,3FH
INT 21H

Output / Return Value

Return:
    CF clear if successful - AX = number of bytes actually read (0 if at EOF before call)
    CF set on error AX = error code (05h,06h)

Limitations

Alternatives / See Also

Reference