2015.8.5 Personal understanding of pointers

1. To distinguish between the type of pointer and the type that the pointer points to

1.1 type of pointer: Remove the pointer name from the pointer declaration statement, and the remainder is the type of the pointer.

Eg:int *a; remove ' a ' to get "int *", so the pointer type is int *, that pointer is a pointer to an integer variable;

char *str; remove "str" to get "char *", so the pointer type is char *, that pointer is a pointer to a char type variable;

int **ptr; remove "ptr" and get "int * *", so the type of pointer change is "int * *, that pointer is a pointer to an integer pointer variable"

int (*PTR) [3]; remove "ptr", get "int (*) [3]", so the type of pointer change is int (*) [3], that is, the pointer is a pointer to an array of integers.

1.2 The type pointed to by the pointer: Remove the pointer's name and the pointer to the left of the pointer declaration in the statement, leaving the type that the pointer points to.

Eg:int *a, remove ' a ' and ' * ', get ' int ', so the type of the pointer is int type;

char *str; remove "str" and "*" to get "char", so the type of pointing is char type;

int **ptr; remove "ptr" and "*", get "int *", so the type of the pointer is int * TYPE;

int (*PTR) [3]; remove "ptr" and "*", get int [3], so the pointer points to an int [3] type.

2. To understand the different meanings of ' * ' on different occasions

1 void Main () 2 {3int *A; 4 int b=ten; 5 6 a=&b; 7 8 printf ("%d", *a); 9 }

Line 3rd int *a (when defined) ' * ' simply means that the variable defined at this time is a pointer variable

The *a in line 8th, where ' * ' means "point", "*a" means the variable pointed to by pointer variable A,which is B;

3, can not give the wild pointer blind assignment value

eg

1 void swap (int *a,int *b)2{3int *  temp; 4 *temp=*p1; 5 *p1=*p2; 6 *p2=*temp; 7 }

Line 3rd defines a pointer to an integer variable, temp, which is then assigned to *temp on line 4th. This is wrong .

Because *temp is the variable pointed to by the pointer temp, the TEMP does not have a definite value because temp is not assigned, so the memory unit that temp points to is unpredictable. The *temp assignment is to assign a value to an unknown storage unit, but this unknown storage unit may be a unit that holds important data, which can cause system errors.

2015.8.5 Personal understanding of pointers