MS-DOS uses INT 21H for its main API functions which provide a low-level is the assembly code to transfer data from one file to other using INT 21H?. INT is an assembly language instruction for x86 processors that generates a software interrupt. For example, INT 21H will generate the software interrupt 0x21 (33 in decimal), causing the function pointed to by the 34th vector in the interrupt. int 21h Dos Interrupt. Int 21h is a common function. The INT 21H instruction in is a software interrupt to vector 21H. It is used for input/output operations.
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INT (x86 instruction)
It takes the interrupt number formatted as a byte value. Instruction Set Reference Manual”. From Wikipedia, the free encyclopedia. Depending on the context, compileror assemblera software interrupt number is often given as a hexadecimal value, sometimes with a prefix 0x or the suffix h.
Other INT instructions are encoded using two bytes. The INT 3 instruction is defined for use by debuggers to temporarily replace an instruction in a running program in order to set a breakpoint.
This page was last edited on 8 Octoberat Sign up using Email and Password. Since the dedicated 0xCC opcode has some inh special properties for debugging, which are not shared by the normal two-byte opcode for an INT 3, assemblers do not normally generate the generic 0xCD 0x03 opcode from mnemonics. For example, INT 21H will generate the software interrupt 0x21 33 in decimalcausing the function pointed to by the 34th vector in the 21y table to be executed, which is typically a DOS API call.
INT (x86 instruction) – Wikipedia
Retrieved from ” https: Thanks in advance for your answer. It comes under type 21h of various interrput tables, hence the lines of code goes like these as you mentioned. INT is an assembly language instruction for x86 processors that generates a software interrupt.
When generating a software interrupt, the processor calls one of the functions pointed to by the interrupt address table, which is located in the first bytes of memory while in real mode See Interrupt vector.
int 21h Dos Interrupt
One of the most useful DOS software interrupts was interrupt 0x Post as a guest Name. Most Unix systems and derivatives do not use software interrupts, with the exception of interrupt 0x80, used to make system calls.