Hello all:
Days ago I posted “How does the RAM work in C++ computing?” This post is
“ How do the global and local variables use the RAM” They are sister questions.
In C++, if a variable is defined outside a function, it is global variable,
e.g. “float glbl[100][500]”. Alternatively Inside a function, it is a local variable ,
e.g. “float lcl[100][500]”
Do they have the same right/passibility to use the RAM?
No. How they end up in RAM is up to the OS.
In C++, all we know is that they are local, static or global. They have different semantics and limitations.
Make no mistake, they all have to end up in RAM somewhere, but how and where? That is a specific question the operating system must answer.
Originally Posted by Adak
Elysia is correct that how memory segmentation is handled is not part of the C or C++ standard. It is determined by the OS, but the OS works according to some conventions determined by how the processor works.
It's probably safe to say that 99.9%+ of contemporary operating systems on common architectures place local variables in the stack segment. Most of them probably also place globals in the data segment.
Memory segmentation - Wikipedia, the free encyclopedia
Any variable has "the right" to use the RAM it has been assigned, but as your last thread might indicate, no variable has the a right to be assigned any memory at all, and if it is not, using it can cause a problem.
If you understand the limitations and set your expectations accordingly, it is not hard to get what you want.
C programming resources:
GNU C Function and Macro Index -- glibc reference manual
The C Book -- nice online learner guide
Current ISO draft standard
CCAN -- new CPAN like open source library repository
3 (different) GNU debugger tutorials: #1 -- #2 -- #3
cpwiki -- our wiki on sourceforge
