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 21h Dos Interrupt
Abraham Jacob 51 1 1. Since the dedicated 0xCC opcode has some desired special properties for debugging, 806 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.
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.
It is therefore entirely possible to use a far-call instruction to start the interrupt-function manually after pushing the flag register. Sign up using Email and Password. By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.
It comes under type 21h of various interrput tables, hence the lines of code goes like these as you mentioned. Sign up or log in Sign up 886 Google. INT is an assembly language instruction for x86 processors that generates a software interrupt.
Other INT instructions are encoded using two bytes. Retrieved from ” https: By calling it with different parameters in the registers mostly ah and al you could access various IO operations, string output and more.
Philip Kirkbride 7, 26 82 Thanks in advance for your answer.
INT (x86 instruction) – Wikipedia
Sign up using Facebook. Email 211h, but never shown. This simply means that you are using function 01h of the Interrupt type 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. Depending on the context, compileror assemblera software interrupt number is often given as a hexadecimal value, sometimes with a prefix 0x or imt suffix h.
assembly language int 21h Dos Interrupt
INT X where X is the software interrupt that should be generated Geoffrey 6, 2 17 This is accomplished by entering a bit value corresponding to a kernel function into the EAX register of the processor and then executing INT 0x I’m new to learning assembly language, and I’m wondering what the command int 21h means. Most Unix systems and derivatives do not use software interrupts, with the exception of interrupt 0x80, used to make system calls.
Stack Overflow works best with JavaScript enabled. Views Read Edit View history. It takes the interrupt number formatted as a byte value. BOSS 8 23 Instruction Set Reference Manual”.
INT (x86 instruction)
This page was last edited on 8 Octoberat For example, INT 21H will generate the software interrupt 0x21 33 in decimalcausing the function pointed to by the 34th vector in the interrupt table to be executed, which is typically a DOS API call. One of the most useful DOS software interrupts was interrupt 0x By using this site, you agree to the Terms of Use and Privacy Policy.
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