SYS03BA: MOV AL,00
SYS03BC: JMP 03C0
Entry point using using DOS Read-Only Access Code (00h).
SYS03BE: MOV AL,01
Entry point using using DOS Write-Only Access Code (01h).
SYS03C0: PUSH BP
Use BP to index items on the stack.
Upon entering this subroutine from any of the entry points: SYS:03BA Read-Only or SYS:03BE Write-Only, and saving BP, the stack looks like this:
| Index | Contents |
|---|---|
| BP | Old BP value |
| BP+02 | Return Address (OFFSET) |
| BP+04 | Return Address (SEGMENT) |
| BP+06 | Pointer to File/Text Record Data (OFFSET) |
| BP+08 | Pointer to File/Text Record Data (SEGMENT) |
SYS03C1: MOV BP,SP
SYS03C3: LES DI,[BP+06]
Loads the pointer to the File into ES:DI.
SYS03C6: ES:
SYS03C7: CMP WORD PTR [DI:Mode],fmInput
SYS03CC: JZ 03E6
Checks if File was opened using Reset().
SYS03CE: ES:
SYS03CF: CMP WORD PTR [DI:Mode],fmOutput
SYS03D4: JZ 03DE
Checks if File was opened using Rewrite().
SYS03D6: MOV WORD PTR [InOutRes],0067
SYS03DC: JMP 03F6
Exit with an error 67h/103: File not open.
SYS03DE: PUSH AX
SYS03DF: MOV BX,0014
SYS03E2: CALL 03FA
SYS03E5: POP AX
Call BX = 0014 InOutFunc() using SYS:03FA I/O Function Dispatcher. This is used to flush the buffer, i.e. write any bytes still left in the buffer.
SYS03E6: OR AL,AL
SYS03E8: JZ 03F6
If Mode = fmInput and Access is Read-Only the return success, otherwise check for errors on Mode = fmOutput.
SYS03EA: MOV BX,001C
SYS03ED: CALL 03FA
Close the File on errors with a call to its BX = 001C CloseFunc() using SYS:03FA I/O Function Dispatcher.
SYS03F0: ES:
SYS03F1: MOV WORD PTR [DI:Mode],fmClosed
SYS03F6: POP BP
SYS03F7: RETF 0004
Return to caller and pop-off parameters.
See also: Text File Type, File Modes, SYS:03FA I/O Function Dispatcher or go back