Compilation Basics (2) 21H interrupts

 

INT 21H Interrupt

AH	Function	Calling parameters	return parameters
xx	program termination (same as int 20H)	cs= program Segment prefix
on	keyboard input and Echo		al= Input Characters
Geneva	Display Output	dl= Output Characters
Geneva	Asynchronous Communication Input		al= input Data
Geneva	Asynchronous communication output	dl= Output Data
to	Printer Output	dl= Output Characters
.	Direct console I/O	dl=ff (Input) dl= character (output)	al= Input Characters
-	keyboard input (no echo)		al= Input Characters
,	keyboard input (no echo) Detection Ctrl-break		al= Input Characters
the	Display String	ds:dx= String Address ' $ ' End string
0A	keyboard input to buffer	ds:dx= Buffer First address (DS:DX) = maximum number of characters in a buffer	(ds:dx+1) = number of characters actually entered
0B	Verify keyboard status		al=00 has input AL=FF No input
0C	clears the input buffer and request the specified input function	al= Input Function number (1,6,7,8,a)
0D	Disk Reset		Purge file Buffers
0E	Specifies the current default disk drive	dl= Drive letter 0=a,1=b,...	number of al= drives
0F	Open File	DS:DX=FCB First Address	al=00 file found al=ff File not found
Ten	Close File	DS:DX=FCB First Address	al=00 Directory modified successfully file not found in Al=ff directory
One	Find First Catalog item	DS:DX=FCB First Address	al=00 found al=ff not found
A	Find Next Catalog Item	DS:DX=FCB First Address (file with * or?)	al=00 found al=ff not found
-	Deleting Files	DS:DX=FCB First Address	al=00 Delete succeeded al=ff not found
-	Sequential Read	DS:DX=FCB First Address	al=00 Read Success = 01 End of file, no data in record =02 DTA space is not enough = 03 End of file, incomplete record
the	Sequential Write	DS:DX=FCB First Address	al=00 Write Success = 01 Disk Full =02 DTA space is not enough
-	Building Files	DS:DX=FCB First Address	al=00 Build Success =ff No disk space
-	file Renaming	DS:DX=FCB First Address (ds:dx+1) = old file name (ds:dx+17) = new file name	al=00 Success Al=ff not successful
+	take the current default disk drive		al= The default drive letter 0=a,1=b,2=c,...
1 A	Place the DTA address	DS:DX=DTA Address
1 B	take the default drive fat information		al= Number of sectors per cluster Ds:bx=fat Identity Byte cx= Physical Sector size dx= the number of clusters for the default drive
1C	take any one of the drive fat information	dl= Drive Letter	Ibid .
+	Random Read	DS:DX=FCB First Address	al=00 Read Success = 01 End of File = 02 Buffer Overflow = 03 Buffer not satisfied
A	Random Write	DS:DX=FCB First Address	al=00 Write Success = 01 Disk Full = 02 Buffer Overflow
at	measure File Size	DS:DX=FCB First Address	al=00 Success (file length filled in FCB) al=ff not found
-	set random record number	DS:DX=FCB First Address
-	Set Interrupt vectors	ds:dx= Interrupt Vector al= Interrupt class model
-	Creating a program segment prefix	dx= new program segment prefix
-	Random block Reading	DS:DX=FCB First Address cx= Record Count	al=00 Read Success = 01 End of File = 02 buffer too small, transfer end = 03 Buffer not satisfied
-	Random block Write	DS:DX=FCB First Address cx= Record Count	al=00 Write Success = 01 Disk Full = 02 Buffer Overflow
in	Parse file name	ES:DI=FCB First Address Ds:si=asciiz String al= Control Analysis Flag	al=00 standard File = 01 Multi-semantic Files = 02 Illegal drive letter
2A	Date Taken		cx= Year dh:dl= Month: day (binary)
2B	Set Date	cx:dh:dl= Year: Month: Day