指针
1 /* 2 ============================================================================ 3 Name : Hello.c 4 Author : 5 Version : 6 Copyright : Your copyright notice 7 Description : Hello World in C, Ansi-style 8 ============================================================================ 9 */ 10 11 #include <stdio.h> 12 #include <stdlib.h> 13 void reset(int i); 14 void reset2(int* p); 15 void add_by_point(int x,int y,int *result); 16 int main(void) { 17 18 printf("%d ",sizeof(char)); 19 printf("%d ",sizeof(int)); 20 int a = 10; 21 int *p1 = &a; 22 char *p2 = p1; 23 24 printf("%d ",p1); 25 printf("%d ",p2); 26 27 printf("%d ",*p1);//10 28 printf("%d ",*p2); 29 30 puts("----------------------"); 31 int c[10] = { 32 1,2,3,4,5 33 }; 34 //数组内容值默认为0 (一组数组a定义10个变量,前5个分别是1,2,3,4,5,那么后六个默认为0) 35 printf("%d ",c[5]); 36 //数组名也是数字首地址(数组名的地址和首个数字的地址一样,比喻:一栋5层楼相当于一组数组,1层、2层、3层、4层、5层相当于变量的地址,那么的地址这栋楼的地址与第一层楼的地址一样。) 37 printf("%d ",c); 38 //指针运算要根据指针的类型(int、float的字节是4个,char的字节是1个,i例如:int类型的a的地址是1,那么a+1的地址是5,如果a类型是char,则a+1的地址是2) 39 printf("%d ",c+1); 40 // 41 printf("%d ",*(c+2));//带*的是求地址里面的内容 42 *(c+2) = 0; 43 printf("%d ",*(c+2)); 44 45 puts("----------------------"); 46 int d = 10; 47 reset(d); 48 //函数独立性 49 printf("%d ",d); 50 reset2(&d); 51 //使用指针的方式突破函数壁垒 52 printf("%d ",d); 53 54 //什么是返回值 55 int e = add(3,5); 56 printf("e = %d ",e); 57 int result = 0; 58 //指针的方式计算结果 59 add_by_point(3,5,&result); 60 printf("result = %d ",result); 61 62 } 63 void reset(int i){ 64 i = 0; 65 } 66 void reset2(int* p){ 67 *p = 0; 68 } 69 70 71 int add(int i,int j ){ 72 /* 73 * 变量的生命周期 74 * 75 * */ 76 77 int q = i+j; 78 return q; 79 } 80 81 void add_by_point(int x,int y,int *result){ 82 int r = (x + y); 83 *result = r; 84 }
/* ============================================================================ Name : hello.c Author : lei Version : 137 Copyright : Your copyright notice Description : Hello World in C, Ansi-style ============================================================================ */ #include <stdio.h> #include <stdlib.h> int main(void) { main2(); return 0; puts("!!!Hello World!!!"); /* prints !!!Hello World!!! */ int i = 10; reset(i); printf("%d ",i); reset2(&i); printf("%d ",i); int a = 10; int b = &a; *(int*)b = 0; printf("%d ",a); int *p; p=b;//p相当于(int*)b *p = 4; printf("%d ",a); /* int c = 0x22336655; int *d = &c; *d = 1; */ char aa = 1; printf("%d ",&aa); return EXIT_SUCCESS; } void reset(int i){ i = 0; } void reset2(int *p){ *p = 0; }
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枚举
1 /* 2 * meiju.c 3 * 4 * Created on: 2017年9月15日 5 * Author: Administrator 6 * 137 7 */ 8 9 enum COLOR { 10 RED,YELLOW,BLUE,GREEN 11 }; 12 13 int favorate_color = RED; 14 void main2(){ 15 16 puts("---------------------"); 17 //枚举内容默认值从0开始,逐步加1 18 printf("%d ",RED); 19 printf("%d ",YELLOW); 20 printf("%d ",BLUE); 21 puts("---------------------"); 22 //枚举内容根据前面的那一个值加1 23 printf("%d ",RED); 24 printf("%d ",YELLOW); 25 printf("%d ",BLUE); 26 27 set_favorate_color(BLUE); 28 29 printf("favorate_color = %d ",favorate_color); 30 31 } 32 33 34 void set_favorate_color(int color){ 35 favorate_color = color; 36 37 }
机房内容
1 /* 2 ============================================================================ 3 Name : xu.c 4 Author : xu 5 Version : 6 Copyright : Your copyright notice 7 Description : Hello World in C, Ansi-style 8 ============================================================================ 9 */ 10 11 #include <stdio.h> 12 #include <stdlib.h> 13 14 int main(void) { 15 puts("Hello UPC World"); /* prints Hello UPC World */ 16 return EXIT_SUCCESS; 17 18 int a = 0;//定义变量a,赋值为1 19 int *p = &a;//定义一个指针,这个指针的内容是变量a的地址 20 *p = 1;//*P是里面的内容,内容是变量a的地址,把1赋值给P*就是修改a的地址 21 22 int b = &b;//定义一个b变量,内容是b的地址 23 *(int*)b = 2;//b是变量,(int*)b是把变量b强制转换为地址,*(int*)b是(int*)b地址的内容,也就是改变量b里面的内容 24 25 puts("----------------------"); 26 enum COLOR { 27 red,bule=3,yellow,green 28 }; 29 //枚举的特性 30 } 31 32 void reset1(int i) 33 { 34 i = 0; 35 } 36 void reset2(int *i) 37 { 38 *i = 0; 39 } 40 void reset3(int i) 41 { 42 *(int*)i = 0; 43 44 }