Question

How to use const pointer to pointer in C

Answer 1

#include <stdio.h>
  
int main(void)
{
    int n = 100;
    const int *p;
    const int **pp;
  
    pp = &p; 
    *pp = &n; 
    
    printf("n = %d\n", n);
    printf("*p = %d\n", *p);
    printf("**pp = %d\n", **pp);

    return 0;
}
  
    
/*
run:
   
n = 100
*p = 100
**pp = 100
 
*/

 

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Answer 2

#include <stdio.h>
  
int main(void)
{
    int n;
    const int *p;
    const int **pp;
  
    pp = &p; 
    *pp = &n;
    **pp = 13; // error: assignment of read-only location

    return 0;
}
  
    
/*
run:
   
 
*/

 

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Answer 3

#include <stdio.h>
  
int main(void)
{
    int n = 98;
    int *p;
    int * const *pp;
  
    pp = &p; 
    *pp = &n; // error: assignment of read-only location ‘*p’ 

    return 0;
}
  
    
/*
run:
   
 
*/

 

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Answer 4

#include <stdio.h>
  
int main(void)
{
    int n;
    int *p;
    int * const *pp;
  
    p = &n;
    pp = &p; 
    **pp = 900; 
    
    printf("n = %d\n", n);
    printf("*p = %d\n", *p);
    printf("**pp = %d\n", **pp);

    return 0;
}
  
    
/*
run:
   
n = 900
*p = 900
**pp = 900
 
*/

 

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Answer 5

#include <stdio.h>
  
int main(void)
{
    int n = 100;
    int *p;
    int ** const pp = &p; 
    
    pp = &p; // error: assignment of read-only variable 'pp'

    return 0;
}
  
    
/*
run:
   
 
*/

 

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Answer 6

#include <stdio.h>
  
int main(void)
{
    int n;
    int *p;
    int ** const pp = &p; 
    
    *pp = &n; 
    **pp = 30; 
    
    printf("n = %d\n", n);
    printf("*p = %d\n", *p);
    printf("**pp = %d\n", **pp);
  
    return 0;
}
  
    
/*
run:
  
n = 30
*p = 30
**pp = 30
 
*/

 

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Answer 7

#include <stdio.h>
  
int main(void)
{
    int n = 99;
    const int *p;
    const int * const *pp;
    
    p = &n;
    pp = &p;
    
    printf("n = %d\n", n);
    printf("*p = %d\n", *p);
    printf("**pp = %d\n", **pp);
  
    return 0;
}
  
    
/*
run:
  
n = 99
*p = 99
**pp = 99

*/

 

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Answer 8

#include <stdio.h>
  
int main(void)
{
    int n = 10;

    const int *p;
    const int ** const pp = &p; 
  
    *pp = &n; 
    
    printf("n = %d\n", n);
    printf("*p = %d\n", *p);
    printf("**pp = %d\n", **pp);
  
    return 0;
}
  
    
/*
run:
  
n = 10
*p = 10
**pp = 10

*/

 

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Answer 9

#include <stdio.h>
  
int main(void)
{
    int n;
    int *p;
    int * const * const pp = &p; 
  
    p = &n;
    
    **pp = 88; 
    
    printf("n = %d\n", n);
    printf("*p = %d\n", *p);
    printf("**pp = %d\n", **pp);
  
    return 0;
}
  
    
/*
run:
  
n = 88
*p = 88
**pp = 88

*/

 

Cleaner teeth, healthier you!
Get The Secret to a Bright and Healthy Smile