C Programming - Structures, Unions, Enums - Discussion

You need to put the statement "void modify(struct emp*);" after declaring struct because the prototype tells the compiler that there is a struct which is mentioned before hence leading to an error. So prog will look like this:


#include<stdio.h>
#include<string.h>

struct emp
{
char name[20];
int age;
};
void modify(struct emp*);
int main()
{
struct emp e = {"Sanjay", 35};
modify(&e);
printf("%s %d", e.name, e.age);
return 0;
}
void modify(struct emp *p)
{
p ->age=p->age+2;
}

#include<stdio.h>
#include<string.h>
typedef struct emp q;
void modify(q *p);
struct emp
{
char name[20];
int age;
};

int main()
{
struct emp e = {"Sanjay", 35};
modify(&e);
printf("%s %d", e.name, e.age);
return 0;
}
void modify(struct emp *p)
{
p ->age=p->age+2;
}

I am not getting any error, and got correct output by using typedef
can anyone explain?

Correct output will be-

sanjay,37

explanation::-all declaration is correct ,like-structure declaration & function declaration(with global scope)

when modify() is called "strupr()" converts "sanjay" into "sanjay"

note:-strupr() is function of <string.h> so it must be included before using it..!!

and p->age=p->age+2;
add 2 in 35 (i.e 35+2=37)

According to explanation...the compiler can't identify the prototype of "struct emp" at the declaration because it's not defined yet. So compiler can't estimate the memory need & tools.

Here because giving typedef it is taking firstly the structure declaration. After then we are declaring above modify function like: void modify(q*p). So we are getting correct o/p.

No Error in the program. We are just instructing the compiler about the prototype of function modify. It is the abstraction so no need to estimate the size of struct emp.

This looks wrong on many counts.

Struct says: char name[20], and yet "Sanjay" is of type (const char *). You're assigning a pointer to an array?

void modify(struct emp*);
has been declared before struct.
if it z declared after struct then the o/p vl be
sanjay 37

Yes, op absolutely sanjay 37, in GCC compiler doesn't shows the error, in turbo c it shows the error.

I agree with rahul there is no error while compiling or executing the program.