数据结构（1）：C语言总结

http://msdn.microsoft.com/en-us/library/cc262957%28v=office.12%29.aspx

指针：

#pragma once
#include <stdio.h>

int main(void){

    int stopFlag = 0;

    int a;
    int *aPtr;

    a = 7;
    aPtr = &a;

    printf("The address of a is %p\nThe value of aPtr is %p", &a, aPtr);
    printf("\nThe value of a is %d\nThe value of *aPtr is %d", a, *aPtr);
    printf("\n\nShowing that * and & are complements of each other\n&*aPtr = %p\n*&aPtr = %p\n", &*aPtr, *&aPtr);

    scanf("%d", &stopFlag);
}

运行结果：

按值传递：

#pragma once
#include <stdio.h>

int cubeByValue(int n);

int main(void){

    int stopFlag = 0;

    int number = 5;
    printf("The original value of number is %d", number);

    number = cubeByValue(number);
    printf("\nThe new value of number is %d", number);

    scanf("%d", &stopFlag);
}

int cubeByValue(int n){
    return n * n * n;
}

运行结果：

按引用传递：

#pragma once
#include <stdio.h>

void cubeByReference(int *nPtr);

int main(void){

    int stopFlag = 0;

    int number = 5;
    printf("The original value of number is %d", number);

    cubeByReference(&number);
    printf("\nThe new value of number is %d", number);

    scanf("%d", &stopFlag);
}

void cubeByReference(int *nPtr){
    *nPtr = *nPtr * *nPtr * *nPtr;
}

运行结果：

最小权限原则(const限定符)：

#1 指向非常量数据的非常量指针：

/*
    using a non-constant pointer to non-constant data
*/
#pragma once
#include <stdio.h>
#include <ctype.h>

void convertToUppercase(char *sPtr);

int main(void){

    int stopFlag = 0;

    char string[] = "characters and $32.98";
    printf("The string before conversion is: %s", string);

    convertToUppercase(string);
    printf("\nThe string after conversion is: %s", string);

    scanf("%d", &stopFlag);
}

void convertToUppercase(char *sPtr){
    while(*sPtr != '\0'){
        if (islower(*sPtr)){
            *sPtr = toupper(*sPtr);
        }
        ++sPtr;
    }
}

运行结果：

 

#2 指向常量数据的非常量指针：

/*
using a non-constant pointer to constant data
*/
#pragma once
#include <stdio.h>
#include <ctype.h>

void printCharacters(const char *sPtr);

int main(void){

    int stopFlag = 0;

    char text[] = "print characters of a string";

    printf("The string is:\n");
    printCharacters(text);
    printf("\n");

    scanf("%d", &stopFlag);
}

/*
sPtr is a "read-only" pointer, cannot modify the character to which it points
*/
void printCharacters(const char *sPtr){
    for (; *sPtr != '\0'; sPtr++){
        printf("%c", *sPtr);
    }
}

运行结果：

#3 指向常量数据的非常量指针（企图修改数据）：

#4 指向非常量数据的常量指针

/*
using a constant pointer to non-constant data
*/
#pragma once
#include <stdio.h>

int main(void){

    int stopFlag = 0;

    int x = 0;
    int y = 0;

    int* const ptr = &x;
    printf("The original value of x is: %d", *ptr);

    x = 5;
    printf("\nThe new value of x is: %d", *ptr);

    scanf("%d", &stopFlag);
}

运行结果：

#5 指向非常量数据的常量指针（企图修改指针）：

#6 指向非常量数据的非常量指针（企图修改数据和指针）：