What are the advantages of INT over CALL?

[matemp]

What are the advantages of INT over CALL? With using CALL it is possible to provide the same actions. What is the fundamental difference between them?
                        Thanks!

[PBrennick]

Do you mean INVOKE?

Paul

[Relvinian]

What are the advantages of INT over CALL? With using CALL it is possible to provide the same actions. What is the fundamental difference between them?
                        Thanks!

There are two major differences between and INT CPU instruction and a CALL instruction.
1) INT is for access "interrupt" driven calls (most notably in DOS mode).
2) CALL is for calling another procedure/function with code and optionally passing parameters (data) to that function.

Does this answer your question?

Relvinian

[matemp]

Is it not possible to call procedures from DOS using CALL instruction and to get the same (as with INT) result?

MAtemp

[hutch--]

MAtemp,

You are mixing up two different technologies from two different operating system types. Real mode DOS used interrupts for both DOS and BIOS functions but 32 bit protected mode does not. Under ring0 there are some system based interrupts but the are not usually used in application programming.

The CALL mnemonic does not more than store the next IP location, branch to another location and on the next RET/RETN it returns to the IP location after the original CALL.

[MichaelW]

Is it not possible to call procedures from DOS using CALL instruction and to get the same (as with INT) result?

It is possible, but to make it work you must effectively simulate an INT with a far CALL. There are at least several methods of doing this, but assuming you avoid tying up a segment register and a base or index register, the simulation requires on the order of 9 instructions. For repeated calls, if the interrupt vector (a far pointer to the interrupt handler) had already been copied to your data segment, each simulation would require 3 instructions:

Code Select Expand


pushf
cli
call int_ptr


[matemp]

Thanks!
                        MAtemp