C pointer and Arrays

Completed: Yes Created: March 30, 2023 Tag: C MOC, C Pointers

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the name of an array, is actually a pointer to the first element of the array.

int array_name[] = {0,1,2,3,4,5};
 
// Get the memory address of the myNumbers array  
printf("%p\n", array_name);  
  
// Get the memory address of the first array element  
printf("%p\n", &array_name[0]);

Output:

0x7ffe70f9d8f0  
0x7ffe70f9d8f0

• the address of &array_name[0] and array_name is the same.
• It’s because the variable name points to the first element of the array.

Similarly:

• &x[1] is equivalent to x+1 and x[1] is equivalent to *(x+1).
• &x[2] is equivalent to x+2 and x[2] is equivalent to *(x+2).
• …
• Basically: &x[i] is equivalent to x+i and x[i] is equivalent to *(x+i).

int array_name[] = {0,1,2,3,4};  
  
printf("%d\n", *(array_name));     // Value of the first element
printf("%d\n", *(array_name + 1)); // Value of the second element
printf("%d\n", *(array_name + 2)); // Value of the third element
printf("%d\n", *(array_name + 3)); // Value of the fouth element
printf("%d\n", *(array_name + 4)); // Value of the fifth element
 

Output:

0x7ffe70f9d8f0  
0x7ffe70f9d8f0

Addres of the elements of an array

int array_name[] = {0,1,2,3,4};
 
printf("%p\n", i, &array_name[0]);  // Addres of the first element
printf("%p\n", i, &array_name[1]);  // Addres of the second element
printf("%p\n", i, &array_name[2]);  // Addres of the third element
printf("%p\n", i, &array_name[3]);  // Addres of the fouth element
printf("%p\n", i, &array_name[4]);  // Addres of the fouth element
 
printf("Address of array x: %p", array_name);

Output:

1450734448
1450734452
1450734456
1450734460
1450734448
Address of array x: 1450734448

• There is a difference of 4 bytes between two consecutive elements of array x.

  • It is because the size of int is 4 bytes (on our compiler).

• Notice that, the address of &x[0] and x is the same. It’s because the variable name x points to the first element of the array.