Josh Koffman wrote 2014-04-06 20:55:

>
> As for variables, I am going to try to be very conscious about how I
> declare them. One thing I'm not entirely sure on, is what if my
> project consists of multiple source files? As an example, suppose I
> have a function in a different file (say, function.c). If I call that
> function from my main loop, how would I have to define the variable?

What variable?
A variable that is (or not) part of the call as a parameter?
A variable that has to be know to both the caller and the called?
A variable that is only used localy withing the function?
Different needs for different uses. :-)

> Do I do it in the main loop, or as a global?

If the declaration and the "use" are in different source file
(that is, in different compiler runs), we go yet another
"step up". What in MPASM is called external/global. The
linker has to be told about that to be able to link it
all correctly. No difference from when linking multiple
ASM routines, actualy!

> I know that technically I
> could craft all my functions to take every single variable as an
> argument, but that seems a bit unwieldy. Generally I keep a few
> registers that I will set bits in for flags on how the program is
> running, or what state it's in. I don't think I've fully grasped what
> it means to declare something volatile, static, or just regular
> global.

It all depends on how and when a variable is used/needed.

As an example, a variable for a normal I/O port (PORTA or
something) is always "volatile" since the value can change
without having a "PORTA=3Dnnn" in the code itself. So the
value of the variable PORTA will never be cached or optimized,
but always (re-) read from the source (the hardware I/O port)
at each access/reference. That is "volatile" !

Same thing for a variable that sudenly could change becuse of
an interrupt. Such code can't be optimized (to much) either.
That is, the use/storage of that variable in main() can not be
optimized, and should be declared volatile as "protection".

And so on... :-)

Jan-Erik.



>
> Thank you again!
>
> Josh
>
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