How to differentiate local copy and global copy of a variable with the same name

[manjuks]

Hi All,

My question is I have one global variable say num, and one local (to main) variable with the same name.

In main how can I access global variable? In C++ ::(scope resolution operator) will avoid this problem, Is there any such operator in C?

Thanks,
Manjunath

[JosAH]

@manjuks
C doesn't have such an operator so you have to 'get out of' your main() function to be able to 'see' your global variable 'sum' again; note that C (and C++) use lexical scoping so any other function that doesn't define an identifier 'sum' can access the global variable.

kind regards,

Jos

[manjuks]

Hi Jos,

Thanks for your reply.

Thanks,
Manjunath

[Banfa]

It would, of course, be better not to have global and local variables with the same name in the first place. In fact some people use a variable naming convention where global variables have a prefix, g or g_ are common, specifically to avoid this and to make the programmer aware when they are using global data.

Another point of view is that global data is generally bad and should just be avoided.

[donbock]

This name-scope issue can be completely local to a single function:

void confusion(int a) {
   ...
   if (a > 0) {
      float a;
      ...
   } else {
      long a;
      ...
   }
   ...
}

Ths function has three different variables named "a", each with a different type. As you move from block to block you gain access to one of these "a" variables but lose access to the others. Such usage may be legal, but it is unwise.