sizeof(char)

*p is a character == 1 byte.
p  is a pointer   == 4 bytes.
&p is an address of a pointer == 4 bytes. Same as char**

sizeof (char)   = 1
sizeof (void *) = 4

sizeof 65; /* same as `sizeof (int);` */
sizeof 'X'; /* same as `sizeof (int);` */
sizeof 42.0; /* same as `sizeof (double);` */
float f;
sizeof f; /* same as `sizeof (float);` */
/* etc ... */

#include <math.h>
sizeof (12 * log(100)); /* same as `sizeof (double);` */
                        /* without the parenthesis, this would be */
                        /* (sizeof 12) * log(100); */

sizeof 'a' == 1   // C++

sizeof 'a' == 4   /* C */