Rules for calling assembly subroutines from, Computer Engineering

Assignment Help:

Q. Rules for calling assembly subroutines from?

The rules for calling assembly subroutines from C are:

(i)  Memory model: The calling program and called assembly programs should be defined with the same memory model. One of the most common convention which makes NEAR calls is .MODEL SMALL, C.

(ii) The naming convention generally involve an underscore (_) character preceding the segment or function name. However this underscore is not used while making a call from C function. Please be careful about Case-sensitivity.

You should give a specific segment name to code segment of your assembly language subroutine. The name differs from compiler to compiler. Microsoft C and Turbo C need the code segment name to be_TEXT or a segment name with suffix_TEXT. Also it needs the segment name _DATA for data segment.

(iii)  Arguments from C to assembly language are passed through stack.

For illustration a function call in C:

function_name (arg1, arg2, ..., argn) ;

Would push the value of every argument on the stack in reverse order. Which is, the argument argn is pushed first and arg1 is pushed last on stack. A pointer or a value to a variable can also be passed on the stack. Because the stack in 8086 is a word stack thuspointers and values are stored as words on stack or multiples of the word size in case value exceeds 16 bits.

(iv) Youmust remember to save any special purpose registers (like CS, DS, SS, ES, BP, SI or DI) which may be modified by the assembly language routine. If you fail to save them then you might have unexplainable / undesirable consequences when control is returned to C program. Though there is no need to save AX, BX, CX or DX registers as they are considered volatile.

(v)   Please note the compatibility of data-types:

            char Byte (DB)

            int Word (DW)

            long Double Word (DD)

(vi) Returned value: The called assembly routine uses the followed registers for returned values:

            char   AL

            Near/ int   AX

            Far/ long DX: AX


Related Discussions:- Rules for calling assembly subroutines from

Sequential logic gates - sr flip flop, Sequential Logic Gates SR flip ...

Sequential Logic Gates SR flip flop                                                                                                                    1)

Boolean algebra, Prove the following Boolean identities using the laws of B...

Prove the following Boolean identities using the laws of Boolean algebra (A + B)(A  + C) = A + BC Ans. (A+B)(A+C)=A+BC LHS AA+AC+AB+BC=A+AC+AB+BC OR  A((C+1)+A(B+1))+BC

What is cache memory, What is cache memory? The small and fast RAM unit...

What is cache memory? The small and fast RAM units are known as caches. When the implementation of an instruction calls for data located in main memory, the data are obtained a

What is a null object in c++, It is an object of a number of classes whose ...

It is an object of a number of classes whose purpose is to indicate that a real object of that class does not exist. One common use for a null object is a return value from a membe

Performance instrumentation, The performance instrumentation states on how ...

The performance instrumentation states on how to efficiently gather information about the computation of the parallel computer. The process of instrumentation mainly attempts to ca

Write an xpath expression, Question: (a) Explain the five different t...

Question: (a) Explain the five different types of element content defined by DTDs. (b) Compare XML schema's against DTDs. (c) Consider the following two element decla

Explain non-folded network, Explain Non-Folded network Non-Folded Netw...

Explain Non-Folded network Non-Folded Network: In a switching network, every inlet/outlet connection may be utilized for inter exchange transmission. In this case, the .excha

Write a program that will solve a puzzle, You will write a program that wil...

You will write a program that will solve a version of the common newspaper puzzle \word search." In the puzzle you are given a grid lled with characters and a list of words to nd

Describe characteristics needed for an e-commerce server, Describe the addi...

Describe the additional characteristics needed for an e-commerce server? E-commerce services need dynamic configuration abilities and seasonal and every day service configurat

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd