User defined data types

Kareem1984 · #1 06-Oct-2004, 18:51

Do I create a struct oustide of my main function?

ie. like this:

CPP / C++ / C Code:

typedef struct element {
	char *data;
	struct element *next;
} LIST; //can this go outside main as well?

void main (void) {

//code

nkhambal · #2 06-Oct-2004, 19:26

Yes, you can do this.

Defining a variable or variable defination outside main() in program file is valid. This way the variable is available for all the functions in the source file i.e. all the function can see LIST definition. Each function can assign its own variable of the type LIST in their code. However these variables will be available only inside those function. In other words, scope of LIST data type is global to program while the locally assigned varibales (inside each function including main()) of type LIST have local scope only inside function.

Following is valid.

CPP / C++ / C Code:

typedef struct element {
char *data;
struct element *next;
} LIST; 

void main (void) {

LIST *anode;

}

void somefunction()
{
 LIST *bnode;
}

This is valid too

CPP / C++ / C Code:

typedef struct element {
char *data;
struct element *next;
} LIST; 

LIST *anode;

void main (void) {

while (anode!=NULL)
{
printf("%s",anode->data);
}

}

void somefunction()
{
 while (anode!=NULL)
{
printf("%s",anode->data); 
}

}

However this is not valid.

CPP / C++ / C Code:

typedef struct element {
char *data;
struct element *next;
} LIST; 


void main (void) {

LIST *anode;

while (anode!=NULL)
{
printf("%s",anode->data);
}

}

void somefunction()
{
 while (anode!=NULL)
{
printf("%s",anode->data);  // Not correct.anode is available only inside main()
}

}

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