Pointers in C

First, the pointer Prelude 1. The importance of pointers

Pointers are a very important type of data in C, and if you say that you have a good study in c except for pointers, you simply say you have not learned C language.

2. Small needs

l void Change (int n) after the function call is complete, the value of the argument is changed

L Analysis: Change the value of the argument, find storage space , address

Second, the pointer variable definition 1. The format of the definition

L class name identifier * pointer variable name;

l int *p;

2. Define the Post assignment first

L Simple Value

int a = 10;

int *p;

p = &a;

printf ("%d", *p);

L Simple Change value

*p = 9;

3. Assigning values at the same time as defined

int a = 10;

int *p = &a;

4. Implement modify argument 5. Watch out.

l int *p; p = 1000;

l int *p; *p = 100;

l int *p; *p = &a;

L%p The address value stored in the output pointer

L Other pointer type description, such as float *p; char *p;

L can not use the type, such as int a = 10; float *p = &a;

6. Clear the pointer

L p = 0;

L p = NULL;

Third, pointer instances

1. void Swap (char *a, char *b) (note temp=a; A = b; b = temp; )
2. int Sumandminus (int a, int b, int *minus)

Iv. the research of pointers

1. Storage space occupied by pointer variables
2. Why are pointer variables typed?

int i = 2;

char c = 1;

int *p = &c;

printf ("%d", *p);

V. Pointers and Arrays 1. Pointer to a one-dimensional array element 2. Traversing one-dimensional array elements with pointers

L Iterate through the char array (' i ', ' t '), and then iterate through the array of int types

the difference between L * (p+i) and * (p++)

L a+i and a++

L p[0],p[1]

3. Exercises

1> Designs a function:int arraysum (int a[], int n), and the number of the first n ofa one-dimensional array . Now replace int a[ with int *p ]

Six, pointers and strings 1. String review

Char s[] = "MJ";

2. Other ways to define strings

Char *s = "MJ";

Or

Char *s;

s = "MJ";

3. The difference between the two ways of definition

L Memory Analysis

L Drawing Analysis

L The difference between a constant and a variable string

L Constant Memory address view

4. Exercises

1> writes an int string_len (char *s)that returns The character length of the string s

Functions for returning pointers

The pointer is also a data type in C, so the return value of a function can certainly be a pointer-type

L The general form of a function that returns a pointer is: type name * Function name ( parameter list )

Eight, pointer to function 1. Why can pointers point to a function?

function as a program, in memory also occupy a portion of storage space, it also has a starting address, that is, the entry address of the function. function has its own address, that's good, our pointer variable is used to store the address. Therefore, a pointer can be used to point to a function. Where the function name represents the address of the function.

2. Definition of pointers to functions

General form of definition: The return value type of the function (* pointer variable name ) ( parameter 1, parameter 2, ...);

3. Use note

L because this type of pointer variable stores the entry address of a function, it makes no sense to add or subtract them (such as p++)

The pointer variable that points to a function has two main uses:

• Calling functions
• Passing functions as arguments between functions

Pointers in C