Question

Here’s my code:

File DataTypes.h

static int count=0;

File TreeOps.h

#include"DataTypes.h"
void printTree(Tree* ptr)

File TreeOps.c

#include"TreeOps.h"
void printTree(pointer){
count++;  // incrementing the count;
printf("%d",counter);
}

File TreeMain.c

#include"TreeOps.h"
printTree(pointer); // all the necessary declarations are done.
printf("%d",count);

If in printTree function the printf gives count=1; while in main function it gives me 0.

Why?

Answer 1

static variable in this context means: every c file has its own variable instance. Remove static definition in h-file:

extern int count;

and add this to one of c files:

int count = 0;

extern means: this is forward declaration. By defining a variable as extern, you tell to compiler that count has int type, and this variable is created somewhere. Actually, this variable is created in one and only one c file. You can use it in any c file where DataTypes.h is included. In the file where this variable is created, compiler uses it. In all other file this variable becomes external reference, which is resolved later by linker.