What is 21H interrupt?
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 function of the MOV 21H?
INT 21H: It is called the DOS function call for keyboard operations follow the function number.
What does mov ah mean?
store
MOV AH, 4CH means store (or “move”) the hexadecimal value 4C into register AH .
What is the action of function 01h of INT 21H?
INT 21h – The general function despatcher
| Action: | Reads a character from the standard input device and echoes it to the standard output device. If no character is ready it waits until one is available. I/O can be re-directed, but prevents detection of OEF. |
|---|---|
| On entry: | AH = 01h |
| Returns: | AL = 8 bit data input |
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 does INT 21h accomplishes if ah contains 4C H?
INT 21h function 4Ch is preferred. Action: Reads a character from the standard input device and echoes it to the standard output device. If no character is ready it waits until one is available.
What is the use of interrupt 21H explain with the help of an example also differentiate between the .COM and .EXE programs?
CP/M Operating System Compatibility The first 100(hex.)/256(dec.) bytes of memory formed a “resident” portion of the Operating System; application programs started in memory at address 100(hex.) Standard application program termination was by “jumping” to address 0, the beginning of the Operating System.
What is interrupt in assembly language?
An interrupt is a condition that halts the microprocessor temporarily to work on a different task and then return to its previous task. Whenever an interrupt occurs the processor completes the execution of the current instruction and starts the execution of an Interrupt Service Routine (ISR) or Interrupt Handler.
Which interrupt called DOS interrupt?
Interrupt vectors used by DOS
| Interrupt vector | Description | Version |
|---|---|---|
| 23h | Control-C handler address | 1.0+ |
| 24h | Critical error handler address | 1.0+ |
| 25h | Absolute disk read | 1.0+ |
| 26h | Absolute disk write | 1.0+ |
What is the function of interrupt 10H?
INT 10h, INT 10H or INT 16 is shorthand for BIOS interrupt call 10hex, the 17th interrupt vector in an x86-based computer system. The BIOS typically sets up a real mode interrupt handler at this vector that provides video services.
What does intint 21h mean?
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 difference between INT 21h / AH=1 and Al 21h?
INT 21h / AH=1 – read Character from standard input, with echo, result is stored in AL. read Character from standard input, with echo, result is stored in AL. INT 21h / AH=2 – write Character to standard output.
What are the control characters for the INT 21h Function?
Many INT 21h functions act upon the following control characters: 08h – Backspace (moves one column to the left) 09h – Horizontal tab (skips forward n columns) 0Ah – Line feed (moves to next output line) 0Ch – Form feed (moves to next printer page) 0Dh – Carriage return (moves to leftmost output column) 1Bh – Escape character
What is the difference between int CX and int 10h/ah?
CX= number of times to write character. INT 10h/ AH = 0Ah- write character only at cursor position. input: AL= character to display. BH= page number. CX= number of times to write character. INT 10h/ AH = 0Ch- change color for a single pixel.