How to define a pointer in the C language?

In the C language, pointers can be defined using the following methods:

1. Declare a pointer variable and initialize it with a data type, followed by the variable name, equals NULL. For example, int *ptr = NULL.
2. To declare a pointer variable without initializing it, use the format: data type *pointer variable name; for example: int *ptr;

When defining a pointer, it is necessary to specify the data type that the pointer points to, and use the * symbol to indicate that the variable is a pointer. The memory address that a pointer variable initially points to is random, so it is usually initialized to NULL.