Sequel to a request on this post, https://www.nairaland.com/2216760/simple-c-codes-still-confuse-me#32101262
I thought it good to reply with a new post, so that a wider community of people can learn.
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Hopefully, this post/reply is brief, concise and not too technical. (experienced programmers too will gain something)
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===== FUNCTIONS and STACK======

----------- A small picture --------
Consider a man named Musa who has to execute some tasks; those tasks are fully wrapped in a box. (Think of each box like a portable version of your local Grinding Machines/Blender where you grind Tomatoes, maize, etc; You know there are different kinds, sizes, and types of grinding Machines, so are there different type of boxes ).

Musa is in a warehose full of Boxes; Now There is long enclosed rail with only one end accessible to Musa where he can push Boxes to, if he wishes; Each box cannot work on its own without a power supply; And the only power supply is at the end of the rail, where Musa sits.

-----Relating the above.....------

Your program starts from the function "main"; in this case, You have given Musa a box to process;
Musa, places the Box on the end of the rail, plugs it and starts processing it. At some point, He reaches a point where he cannot proceed without the result of another function(Box); He then stops there; but He is given some data (lets say Tomatoes) to call the other function with;

Musa unplugs "main" and pushes it further into the rail... then gets up and walks through the warehouse in search of the Box he needs to proceed. He retrieves it and brings it to his desk; Lays it on the end of the rail. remember, "main" has been pushed further into the rail. He plugs the new function(box) into the power supply, pours the Tomatoes into it and starts processing....

If He reaches a point where he needs, another function to proceed, ...then the entire process is repeated until the functions starts returning (i.e a function executed to completion)...
When a function is returning... Musa collects the results(lets say result of grinding tomatoes and onions); then He cleans up that machine(Box). Unplugs it and returns it to the warehouse floor. He then rolls the rail forward until the last Box He was using pops out. He connects it, and continues from where He stopped, this time with the results of the previous function. Hence, he can proceed. :-)

Now, that my friend, is a function and a stack. !
The rail, is your stack, the boxes are your functions!

When we are returning from a function(cleaning up the machines), Destructors of objects are called. (In C++ and D).
We can simply view a stack as part of your RAM that is grows and shrinks with respect to function calls;

======= Extras ========
- There is something called stack unwinding. This simply means the minimum work you must do to remove boxes from the rail.
- There is something called stack overflow. This simply means having too much items on your rail to extents that it's full, therefore, preventing you to push more boxes into it.
- When a program is multi-threaded, it means, you have multiple Threads(box rails) and Executors(Musa)
- Functions may be inlined, meaning boxes embedded in boxes, thus Musa, doesn't have the burden of going to look for it.
- Every program starts with a function. (some may be in a global disguise, like scripting languages)

======= Technical =======
- Functions are fast because, every variable inside is addressed in a very simple fashion; relative offsets;
The CPU simply reads from direct offsets in order to retrieve the value you want to read;
Interestingly, (most at times) the data doesn't need to be re-read from RAM, because while the function is fetched, the entire function block will (almost always) be fetched from RAM into the CPU's memory(cache).

- One key difference that makes C++ faster than Java(not always); and Java faster than Python(not always) is in the way they resolve their functions;

- C++ knows exactly where the function is at every call site. and calls them directly (non virtual functions);
- Java looks the function up in a Virtual table (jumps to an offset, to find the exact position of the function);
- Python looks up a dictionary, does some calculations, and jumps to the function's call site

Note: These are traditional ways these languages work. But on good days (most of the time), they are able to make direct calls, hence as fast as C++;

If You are REALLY interested in the ADVANCED stuff, head to http://en.wikipedia.org/wiki/Call_stack ...start from there and dig in deeper.

==============
From a Machine's point of view, a function is basically any well defined cluster of (instruction and data).
What I mean is, A function is an executable region in memory.
==============

Congrats to our dear Nation Nigeria, on her Presidential Elections.

Regards,
Timothy

thanks for the write up!

it is fully mapped into the layman's domain (abastraction ), concise and easy to understand, thanks once more.

Lovely write up Whiztim .. Learned something new today

Need your advise pls...

we've been taught only Pascal in school but I've picked up C++, I wanna be a software developer , what are the other essential things I need to learn apart from C++?

prinzfunchi:
Lovely write up Whiztim .. Learned something new today

Need your advise pls...

we've been taught only Pascal in school but I've picked up C++, I wanna be a software developer , what are the other essential things I need to learn apart from C++?

This is over two years now... I am sorry for not responding since ....#facepalm
How's the C++ coming? Its two years now, you should prolly be a don by now

Rewrote this on my blog...
Found here: http://whiztim.com/Laymans-Explanation-To-Functions-And-Stack/

WhiZTiM:


This is over two years now... I am sorry for not responding since ....#facepalm
How's the C++ coming? Its two years now, you should prolly be a don by now

lol. i moved from C++ to Java and I'm an Android developer now

thanks for replying

Very wonderful. Thanks...

Simple function and explanation are filed for automatic means and all offers for designated personalities. The room for the success of https://www.topdissertations.org/edubirdie-review/ is improved for all chips in life. The design is divided with the help of the pure and all incentives based terms for members. the struggle is respected and instilled in the advancement of the concepts for all factors of life and society.

prinzfunchi:
Lovely write up Whiztim .. Learned something new today

Need your advise pls...

we've been taught only Pascal in school but I've picked up C++, I wanna be a software developer , what are the other essential things I need to learn apart from C++?

FPC is also a good language.Why don't u wanna go with it?

prinzfunchi:


lol. i moved from C++ to Java and I'm an Android developer now

thanks for replying

Cool u.
So what apps or projects have u done in Android?