What does int 21h mean in assembly language?
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 of 4ch under INT 21h?
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.
For what purpose are these lines used int 21h Mcq?
INT 21H means invoke the interrupt identified by the hexadecimal number 21 .
What is the purpose of INT 04H?
# 03H and 04H – Auxiliary input/output – INT 14H is preferred. # 06H- Direct keyboard and display – Displays the character in DL.
Which INT 21h function is to get system time?
DOS INT 21h services
| AH | Description | Version |
|---|---|---|
| 2Bh | Set date | 1.0+ |
| 2Ch | Get time | 1.0+ |
| 2Dh | Set time | 1.0+ |
| 2Eh | Set verify flag | 1.0+ |
What is the function of MOV A 21h?
What is the function of MOV A 21H?
| Function number | Description |
|---|---|
| 01h e.g. mov ah,01h int 21h | Keyboard input with echo: This operation accepts a character from the keyboard buffer. If none is present, waits for keyboard entry. It returns the character in AL. |
What does the INT 21h accomplish if ah contains a 4Ch?
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. END denotes the end of the program.
What is INT 21h and INT 10H?
Use INT 10H function calls to: – Clear the screen. Use INT 21H function calls to: – Input characters from the keyboard. – Output characters to the screen.
Which INT 21H function is to get system time?
What is INT 21H and INT 10H?
Why is the DOS Function 4Ch used?
Use function 4Ch instead. Description: This function will read a single character from the standard input device. If no character is waiting to be read, it will wait until a character becomes available. Description: This function will write the specified character on the standard output device.
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.
Are there any non functional functions in INT 21h?
INT 21h in the 512’s implementation of DOS Plus 2.1 provides 77 official functions, two of which are non-functional and return with no action. Within this range some calls have subfunctions which further extend the range of operations. In all calls, on entry AH defines the function.
What are the control characters of INT 21h?
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
Which is better INT 21h or INT 4CH?
INT 21h function 4Ch is preferred. 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.
How to call program terminate routine INT 21h?
In all cases the general programming technique is to set AH to the function pointer, set up the required register contents (and the memory block if necessary) then to issue the call by the assembly code INT instruction. To call the recommended program terminate routine, INT 21h function 4Ch, the relevant parts of the code would be:
