Simple question on Ram use

[Gabriel]

Hey all,

regarding Ram usage,

does returning a value from a function type int save any ram?

for example doing something like this:

[SherpaDoug]

Many PICs have unused bits in some registers. The CCS compiler is smart enough to put the first few type short variables in those bits if they are available. So depending on your choice of PIC a few shorts may require no RAM at all. After that the compiler will group shorts compactly into bytes as needed whether they are declared as a group or not.

I don't really understand your first question. But whatever it is you can probably find out by compiling a couple of short test programs, one returning ints and the other using an alternative.
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[ckielstra]

Global variables are using a fixed amount of RAM.
A variable returned from a function is placed on the stack and this space can be re-used. So yes, normally RAM is saved by returning variables instead of using global variables.

Questions like this can be tested yourself by compiling the application for both situations. Check the top of the generated list file (*.lst) for the amount of RAM used, and compare the results for both programs.

Regarding the 1-bit flags, here the compiler will try to combine multiple flags into one byte. However, there is no guarantee in how good the compiler will do this, one compiler version may do it better/worse than the next.
Again, you can test this yourself.
Have a look at the generated symbol file (*.sym) for the addresses used for your variables, when combined into a single byte you will see the flags use the same address.

[Gabriel]

Thank you both for your answers...

I appreciate it.

Gabriel.
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CCS PCM 5.078 & CCS PCH 5.093