Upon entry the stack looks like this:
| Index | Contents |
|---|---|
| SP | Return Address (OFFSET) |
| SP+02 | Return Address (SEGMENT) |
| SP+04 | Pointer to File/Text Record Data (OFFSET) |
| SP+06 | Pointer to File/Text Record Data (SEGMENT) |
SYS0480: MOV BX,SP
Use BX to address items in the stack.
SYS0482: SS:
SYS0483: LES DI,[BX+04]
Loads the pointer to the File into ES:DI.
SYS0486: ES:
SYS0487: MOV BX,[DI:Handle]
Loads the (Handle) in File into BX.
SYS0489: CMP BX,+04
SYS048C: JBE 0494
Check if Handle is a standard handle provided by DOS and return immediately if it is.
SYS048E: MOV AH,3E
SYS0490: INT 21
Close file handle using DOS INT 21h AH = 3Eh service with parameter BX = File handle.
SYS0492: JB 0496
Exit with a DOS Error code in AX if an error occured.
SYS0494: XOR AX,AX
AX = 0 (No errors).
SYS0496: RETF 0004
Return and pop-off parameters from the stack. The error code in AX is later stored in InOutRes.
See also: Text File Type or go back