Parameter Coordination

Table 20.1 lists the main conventions on passing parameters to the procedure. Notice that in all Assembly programs presented in this book, the stdcall type for passing parameters was specified. However, this convention isn't used practically because parameters are passed and retrieved explicitly without the translator's help. When dealing with high-level languages, this must be taken into account. Therefore, the programmer must know how calling conventions work.

Table 20.1: Calling conventions

Convention	Parameter	Clearing the stack	Register
Pascal (the convention adopted in Pascal)	From left to right	Procedure	None.
Register (register or fast calling convention)	From left to right	Procedure	Three registers are employed ( EAX, EDX , and ECX ); if these registers are not sufficient for passing all parameters, then the remaining parameters are passed through the stack.
Cdecl (C convention)	From right to left	Calling program	None.
Stdcall (standard call)	From right to left	Procedure	None.

This table clearly explains the conventions on calling functions and on passing parameters, so it doesn't need additional clarification .

I'd like to draw your attention to another important aspectnamely, the types of return values. In Assembly language, everything is simple: The value returned in the EAX register can be either a number or a pointer to some variable or structure. If the return value has the WORD data type, it is passed in the least significant word of the EAX register. However, if you are dealing with the C programming language, you should pay attention to the problem of type casting. Type casting can be considered an art or a science, but unfortunately , in this book I can't pay it the attention that it deserves .