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cpointersconstants
Vinod
Vinod

Reputation: 4352

Behaviour of const int pointer - C

I have a C program

#include<stdio.h>

void f(const int* p)
{
  int j;
  p = &j;
  j = 10;
  printf("Inside function *p = %d\n",*p);
  *p = 5;
  printf("Inside function *p = %d\n",*p);
  j = 7;
  printf("Inside function *p = %d\n",*p);
}

int main()
{
  int i = 20, *q = &i;
  f(q);
}

Compilation of the program gives the error

Assignment of the read only location *p

at the line *p = 5;

Why is that the assignment j = 10; is valid and *p = 5; is an error.

Upvotes: 0

Views: 172

Answers (3)

Waqar Ahmed
Waqar Ahmed

Reputation: 5068

const int mean , its value remain same until program ends so you can not change its value.

Upvotes: 0

djhaskin987
djhaskin987

Reputation: 10107

const int *p means that you can't modify the integer that p is pointing to using p, as in *p = 5;. The integer it points to may not be a const int, which is why j = 10 works. This prevents coders from modifying integer being pointed to.

Upvotes: 5

michaeltang
michaeltang

Reputation: 2898

const int* p mean you can not change the content in the address of p

which is you can not chanage *p

Upvotes: 2

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