C Programming - Typedef - Discussion

typedef char *charp=> charp is character pointer
but
const charp P => P it is simply constant

P is a constant because it defines.

And it's a type of pointer type.

P is a constant pointer.

'const charp p' doesn't translate to 'const char* p'

Think of it this way:

const int x;//means x is an integer constant.
const charp p;//means p is a charp constant.

The purpose of typedef is to form complex types from more-basic machine types and assign simpler names to such combinations.[wikipedia]

It doesn't just carry out string substitution like #define Macros.

C program to buttress my point.

#include<stdio.h>
int main()
{
typedef char *charp;
const charp p="ABCD";
p="XYZ";
printf("%s",p);
return 0;
/*output is a compiler error stating that p is read-only.
so assigning "XYZ" is illegal*/
}

However,

#define charp char*
#include<stdio.h>
int main()
{
const charp p="ABCD";
p="XYZ";
printf("%s",p);
return 0;
/* executes fine. output is XYZ*/
}

const p;

The syntax itself having the keyword "const" which indicates the constant values.

Please tell me whether p is a character constant or simply a constant.

What is char P?

Why p is not character constant here.

Because according to def of typedef it will change name from char* to chptr then it will be const char*p.

So simple dear, typedef is type replacement means:

charp replace with char * so it becomes.

const char *P; (pointer always reads from left to right).

Value can't change (pointer to character constant).

How is this possible?

Can someone explain clearly?