Structuring

These are opcodes, etticates and  features necessary to divide assembly program in different structures like subroutine and for handling
those procedure. The minimum opcodes necessary for an assembly procedure are:

CALL, RET, 


# CALL

Syntax:
	call <lebel>
	
CALL saves the current CPU state in the stack and jumps to the memory address pointed to by <label>, which can be direct memory address as
well as a register if its holding a memory address. The main difference between CALL and jumps instructions is, CALL is designed to call
procedures, so it saves the current CPU/Core state before making the jump. 



# RET

Syntax:
	ret

RET is the reciprolcal opcode of CALL. When encountered, the CPU loads the previous CPU state from stack and jumps back to the address stored 
at the top of the stack, thus returning to the calling function. RET can also take an optional argument.


# Local lebels:
---------------
	Local lebels start with a "." and only visible from the global lebel immediately preceeding it. Example:
		NewMag:
			.
			.
			.
		Rotation:
			.
			.
			.
		.DoCycle:
		 .	.  .
		NewPeg:

Here in this example the lebel ".DoCycle" is only visible from the global lebel "Rotation". Its invisible from "NewMag" and "NewPeg". So, this
".DoCycle" lebel is local to global lebel "Rotation".


# Libraries:
------------
	Usually a C/C++ or JAVA program can be divided into different files: one contains the main() other contains definations or declarations 
of necessary function and classes that is necessary for the main() to work. Similarly an assembly program can be divided into different files.
One of them contains _start(). Others contains various procedures and data necessary for the program to work. For this:

1) Lebels (designating procedure or data) that are defined in a seperate file but will be used in current file must be followed by "extern"
modifier. Example:

	extern ThisDate
	extern DoThis, OtherWork
			.
			.
			.
	CurrentProcedure:
		.  .  .
		call DoThis
		.  .  .
		mov rax, [ThisDate]
		.  .  .
		call OtherWork
		.  .  .

The variable "ThisDate" and functions "DoThis" and "OtherWork" are described in a seperate file. So to use them is current listing they must
be designated "extern".

2) Lebels that are to be used by other files but are defined in current folder must be followed by "global" modifier. Following from previous
example, the extern lebels must be declared as:

	global ThisDate
	global DoThis, OtherWork

In the file where they are defined.