What is the difference between char array and char pointer in C?

c arrays pointers
diesel picture diesel · Apr 17, 2012 · Viewed 366.2k times · Source

I am trying to understand pointers in C but I am currently confused with the following:

  • char *p = "hello"

    This is a char pointer pointing at the character array, starting at h.

  • char p[] = "hello"

    This is an array that stores hello.

What is the difference when I pass both these variables into this function?

void printSomething(char *p)
{
    printf("p: %s",p);
}

Answer

Jon picture Jon · Apr 17, 2012

char* and char[] are different types, but it's not immediately apparent in all cases. This is because arrays decay into pointers, meaning that if an expression of type char[] is provided where one of type char* is expected, the compiler automatically converts the array into a pointer to its first element.

Your example function printSomething expects a pointer, so if you try to pass an array to it like this:

char s[10] = "hello";
printSomething(s);

The compiler pretends that you wrote this:

char s[10] = "hello";
printSomething(&s[0]);

Related questions

How to find the 'sizeof' (a pointer pointing to an array)?

First off, here is some code: int main() { int days[] = {1,2,3,4,5}; int *ptr = days; printf("%u\n", sizeof(days)); printf("%u\n", sizeof(ptr)); return 0; } Is there a way to find out the size of the array that ptr is pointing …

Read More
C pointer to array/array of pointers disambiguation

What is the difference between the following declarations: int* arr1[8]; int (*arr2)[8]; int *(arr3[8]); What is the general rule for understanding more complex declarations?

Read More
Returning an array using C

I am relatively new to C and I need some help with methods dealing with arrays. Coming from Java programming, I am used to being able to say int [] method()in order to return an array. However, I have found …

Read More