A simple example of a C language pointer

The presence of C language pointers makes the control of hardware and the flexibility of C language greatly improved.

However, there are many difficult problems in the use of pointers.

#include <stdlib.h>#include<stdio.h>//The function here is an example of a pointer doing a parameter, knowing that this feature can compensate for the ability of a C language to have only one return value. voidSWAP1 (int*PA,int*pb) {    intT =*PA; *pa=*PB; (P =t;}//The main () function must return a numberintMain () {intA = the; intb=Ten; int*T; T=&b; A=b; b=*T; printf ("%d\n", B); Swap1 (&a,&b); printf ("%p\t%p", A, b); return 0;}

Here we first define two integer variables, a, b

Then define a temporary pointer variable to store the intermediate variable

Then assign the memory address of variable B to t, note that T is the memory address

Then give the value of B to a, and then B to accept the variables stored in the T address, note that the *t here refers to the variable referred to in the address of T.

Pointers and Arrays

In fact the array of int a[10];

A is actually a pointer to the a[0] of the first element of the array.

So the array variable itself is the expression address, so

1   inta[Ten];2   int*p=a;//no need to take & address3 4But the elements of the array are the variables that need to be used &Fetch Address5a==&a[0];6 7 The [] operator can do the array, or it can do the pointer:8 9 Tenp[0] <==>a[0]; OneHere's p[0Equivalent toP A  -*a can represent a[0] -  theThe array variable is a const pointer

The function of the const modifier is to indicate that a variable is a specified value that cannot be changed.

int Const // p is a const*q=; // OK // ERROR

1   intls= -;2     intls1= -;3     int*Constq=&ls;4*q =Ten;5*q= -;6 //q = &ls1; This sentence cannot be compiled because the pointer is not an address that can point to another location7     //execution success indicates that the pointer variable here can be changed8ls= $ ;9printf"\n%d",*q);Ten     //and then we'll look at another situation . One     intp1=Ten; A     intP2= -; -     int Const*t=&P1; -t=&p2;//execution result is the     //*t = 15; Here is not compiled, because the pointer to the location of the stored variables can not be assigned to change the value.  -P2= -;  -printf"\n%d",*T); -     //The key is that the const here is in front of the * or behind the decision +     return 0;

1 void mai (constint*p) {2        3        int *ls=*   4            printf ("LS's address:%p", ls); 5  6 Here we pass in a pointer, but in a function, you cannot change the value that the pointer points to.

Operation of Pointers

1#include <stdio.h>2#include <stdlib.h>3 4 intMain () {5     inti,j;6I=Ten; j= A;7printf"i,j:%d,%d\n",&i,&j);8printf"i,j:%d,%d", *&i+1,&j);9printf"\n&i-&j:%d", (&i)-(&j));//Here are two address differences are actually the address difference/type occupies the number of digitsTen  One     int*p; Ap=&i; -*p++;//is actually * (p++); + + priority is higher than *; array traversal -printf"\n*p:%d",*p); the     return 0; -}

Type conversions for pointers

void* A pointer to something that doesn't know what it's pointing at.

The size of the pointer variable is the same, but the pointer is of a different type

In short, the role of pointers

1 and need to pass in large data when used as parameters 2 , array operation after passing in 3 , the function returns more than one time can be carried out with the pointer (C can only return a variable, or value)     Need to use function to modify more than one variable 4, dynamic request memory ....

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A simple example of a C language pointer