Question

What is difference between uninitialized pointer and null pointer in C

Answer 1

Uninitialized pointer points to unknown memory location, and null pointer points to null value

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Answer 2

#include <stdio.h> 

// Uninitialized pointer points to unknown memory location, and null pointer points to null value

int main(int argc, char **argv) 
{ 
    int *p; // Uninitialized pointer
    int *np = NULL; // Null pointer
        
    printf("%d\n", (int)sizeof(p));     
    printf("%d\n", (int)sizeof(np)); 
    
    printf("%p\n", p); // warning: 'p' is used uninitialized in this function 
    printf("%p\n", np);
    
    // Error program crushed:
    //*p = 100;
    //*np = 33;
    //printf("%d\n", *p); 
    //printf("%d\n", *np);
        
    return(0);
}

 
 
/*
 
run:
 
8
8
0000000000000000
0000000000000000
 
*/

 

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