What does int 21H mean in assembly language?

int 21h means, call the interrupt handler 0x21 which is the DOS Function dispatcher. the “mov ah,01h” is setting AH with 0x01, which is the Keyboard Input with Echo handler in the interrupt.

What is the function on int 21H?

INT 21h – The general function despatcher

Action:	Reads a character from the standard input device without copying it to the display. If no character is ready it waits until one is available.
On entry:	AH = 08h
Returns:	AL = 8 bit data input
Notes:	If CTRL-C is detected INT 23h is executed.

Which DOS int 21H command is write a character to output?

2
INT 21h / AH=2 – write character to standard output. entry: DL = character to write, after execution AL = DL.

What is the function of 4CH and int 21H?

3 Answers. MOV AH, 4CH means store (or “move”) the hexadecimal value 4C into register AH . INT 21H means invoke the interrupt identified by the hexadecimal number 21 .

What is INT 21h and INT 10H?

Use INT 10H function calls to: – Clear the screen. – Set the cursor position. – Write characters to the screen in text mode. Use INT 21H function calls to: – Input characters from the keyboard. – Output characters to the screen.

What is ah in assembly language?

al and ah are the 8-bit, “char” size registers. al is the low 8 bits, ah is the high 8 bits. They’re pretty similar to the old 8-bit registers of the 8008 back in 1972.

What is Int 20h in assembly language?

The int 20h is the “exit program” system call. One theory is that it is placed at offset 0000h so that if execution runs off the end of the code segment, the instruction pointer will wrap back around to zero, and then the program will terminate.

What is mov ah in assembly language?

mov ah,4ch is the first line of assembler code. The value 4C in hexadecimal is stored in the register AH. int 21h is the second line of assembler code. The software interrupt 21h is called. This interrupt, when given the value of 4ch in AH (as is the case here), causes the program to exit immediately.

What does int 0x10 do?

Each INT represents a functions family, where usually AH represents the function number. For example : INT 0x10 is used for screen manipulation.

Which of the following is BIOS level interrupt?

The BIOS increments the time-of-day counter during this interrupt. This is the Keyboard interrupt. This is generally triggered when a key on a keyboard is pressed….Interrupt table.

AH	Description
01h	Read Input Status
02h	Read Keyboard Shift Status
05h	Store Keystroke in Keyboard Buffer
10h	Read Character Extended

What is mov ax @data in assembly language?

MOV AX,@DATA is the first line of code that gets run. I believe @DATA is a variable that holds the value of the location in memory where the data segment lives. It moves the memory location of @DATA into the AX register (16 bit register).

What are AH and AL?