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Scope Rules

A scope in any programming is a region of the program where a defined variable can have
its existence and beyond that variable it cannot be accessed. There are three places where
variables can be declared in C programming language:
 Inside a function or a block which is called local variables,
 Outside of all functions which is called global variables.
 In the definition of function parameters which are called formal
parameters.
Let us understand what are local and global variables, and formal parameters.

Local Variables
Variables that are declar

ed inside a function or block are called local variables. They can be used only by
statements that are inside that function or block of code. Local variables are not known to
functions outside their own. The following example shows how local variables are used. Here all
the variables a, b, and c are local to main() function.

#include <stdio.h>

int main ()
{

/* local variable declaration */
int a, b;

int c;

/* actual initialization */
a = 10;

b = 20;
c = a + b;

printf ("value of a = %d, b = %d and c = %d\n", a, b, c);

return 0;

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