Pointer ---------- pointer in c, pointer, pointer array, and array pointer

Pointer ---------- pointer in c, pointer, pointer array, and array pointer
1. If a pointer defines a variable in the program and compiles the program, the system will automatically allocate memory units to the variable and allocate space of different lengths according to different types, for example, int occupies 4 bytes and char occupies 1 byte. Each byte in the memory unit has a number, which is the address. Because you can find the desired Variable unit through the address, it can be said that the address points to the variable unit. For example, a room number 301 is hung at the door of a room, which is the address of the room. This address is visualized as a pointer. For a memory unit, the address (number) of the Unit is the pointer, and the data stored in the unit is the content of the unit. Strictly speaking, a pointer is an address and a constant. A pointer variable can be assigned different pointer values, which are variables. However, pointer variables are often referred to as pointers. To avoid confusion, it is agreed that "Pointer" refers to an address, a constant, and "pointer variable" refers to a variable whose value is an address. The purpose of defining pointers is to access memory units through pointers. For example: int a = 12; int * p = & a; 2. pointer (second-level pointer) in simple terms, second-level pointer variable is the address of the first-level pointer variable. Example: int a = 12; int * p = & a; int ** = & p;