本文主要是介绍c语言基础,对大家解决编程问题具有一定的参考价值,需要的程序猿们随着小编来一起学习吧!
1.HelloWorld
#include <stdio.h> //相当于java导包 standard io java.lang
#include <stdlib.h> //standard lib
main(){
//控制台打印语句
printf("HelloWorld\n");
//执行windows指令
system("pause");
}
2.C的基本数据类型
#include <stdio.h>
#include <stdlib.h>
main(){
//char, int, float, double, long, short, signed, unsigned
signed int i = 3;
//无符号只是注明最高位是数值位,但不会改变二进制表示的取值
unsigned int i2 = 4200000000;
char c = 'a';
long long ago = -420000000;
printf("i的值为%d\n", i);
printf("i2的值为%u\n", i2);
printf("c的值为%c\n", c);
printf("short的长度为%d\n", sizeof(short));
printf("int的长度为%d\n", sizeof(int));
printf("long的长度为%d\n", sizeof(long));
printf("float的长度为%d\n", sizeof(float));
printf("double的长度为%d\n", sizeof(double));
printf("char的长度为%d\n", sizeof(char));
printf("long long的长度为%d\n", sizeof(long long));
printf("long int的长度为%d\n", sizeof(long int));
printf("short int的长度为%d\n", sizeof(short int));
system("pause");
}
3.输出函数
#include <stdio.h>
#include <stdlib.h>
main(){
/*
%d - int
%ld – long int
%lld - long long
%hd – 短整型
%c - char
%f - float
%lf – double
%u – 无符号数
%x – 十六进制输出 int 或者long int 或者short int
%o - 八进制输出
%s – 字符串
*/
int i = 3;
long int ld = 334;
long long lld = 4200000000;
short s = 245;
printf("%d\n", i);
printf("%ld\n", ld);
printf("%lld\n", lld);
printf("%hd\n", s);
char c = 'a';
printf("%c\n", c);
float f = 3.14666666;
double d = 3.14666666;
printf("%f\n", f);
printf("%lf\n", d);
printf("%#x\n", ld);
printf("%#o\n", ld);
//C的字符串是字符数组
//字符数组末尾一定有一个结束符“\0”
char str[] = "sb光头鹏";
printf("%s\n", str);
system("pause");
}
4.输入函数2
#include <stdio.h>
#include <stdlib.h>
main(){
printf("请输入班级人数:");
int count;
//取出count的内存地址,把用户输入的数据保存在这个地址上
scanf("%d", &count);
printf("请输入班级名称:");
//定义字符数组,必须指定长度
//C的数组不检测越界
char name[7];
scanf("%s", &name);
printf("count的地址为%#x\n", &count);
printf("name的地址为%#x\n", &name);
printf("班级人数为:%d,班级名称为%s\n", count, name);
system("pause");
}
5.内存地址
#include <stdio.h>
#include <stdlib.h>
main(){
int i;
i = 3;
printf("%d\n", i);
printf("%#x\n", &i);
system("pause");
}
6.内存修改器
#include <stdio.h>
#include <stdlib.h>
main(){
int time = 60;
int i;
printf("%#x\n", &i);
for(i = time; i > 0; i--){
printf("剩余时间为%d\n", i);
sleep(2500);
}
system("pause");
}
7.指针
#include <stdio.h>
#include <stdlib.h>
main(){
int i;
i = 3;
//定义一个指针变量
int* p = &i;
//定义一个二级指针
int** q = &p;
printf("%d\n", i);
printf("%#x\n", &i);
printf("%#x\n", p);
printf("%d\n", *p);
printf("%d\n", **q);
system("pause");
}
8.常见错误
#include <stdio.h>
#include <stdlib.h>
main(){
int* p;
int i = 3;
double d = 3.14;
p = &i;
double* q = &d;
printf("%#x\n", q);
printf("%lf\n", *q);
system("pause");
}
9.值传递和引用传递
#include <stdio.h>
#include <stdlib.h>
void function(int* p, int* q){
int temp = *p;
*p = *q;
*q = temp;
}
main(){
int i = 3;
int j = 5;
function(&i, &j);
printf("i的值为%d\n", i);
printf("j的值为%d\n", j);
system("pause");
}
10.返回多个值
#include <stdio.h>
#include <stdlib.h>
void function(int* p, int* q){
*p = *p * 2;
*q = *q * 2;
}
main(){
int i = 3;
int j = 5;
function(&i, &j);
printf("i的值为%d\n", i);
printf("j的值为%d\n", j);
system("pause");
}
11.在主函数中获取子函数的变量的地址
#include <stdio.h>
#include <stdlib.h>
void function(int** p){
int i = 3;
*p = &i;
printf("子函数打印地址%#x\n", &i);
}
main(){
int* mainp;
function(&mainp);
printf("主函数打印地址%#x\n", mainp);
printf("i的值为%d\n", *mainp);
system("pause");
}
12.数组
#include <stdio.h>
#include <stdlib.h>
main(){
//char c[] = "hello";
int c[] = {1,2,3,4,5};
printf("%#x\n", &c[0]);
printf("%#x\n", &c[1]);
printf("%#x\n", &c[2]);
printf("%#x\n", &c[3]);
printf("%#x\n", &c);
//字符数组的地址,就是第一个字符的地址
int* p = &c;
//c+1表示位移一个单位,一个单位是几个字节根据指针类型决定
printf("第0个元素的值%d\n", *(p + 0));
printf("第1个元素的值%d\n", *(p + 1));
printf("第2个元素的值%d\n", *(p + 2));
printf("第3个元素的值%d\n", *(p + 3));
printf("两个地址的距离%d\n", (p + 3) - (p + 1));
system("pause");
}
13.指针长度
#include <stdio.h>
#include <stdlib.h>
main(){
//指针长度为4个字节,因为32位环境,内存地址长度就是4
printf("int*的长度是%d\n", sizeof(int*));
printf("double*的长度是%d\n", sizeof(double*));
int i = 3;
int j = 5;
//不是连续空间的地址,不能做指针运算
printf("%#x\n", &i);
printf("%#x\n", &j);
printf("两个地址的距离%d\n", &i - &j);
system("pause");
}
14.申请堆内存
#include <stdio.h>
#include <stdlib.h>
main(){
//申请12个字节的堆内存 ,此函数返回堆内存的首地址
int* p = malloc(3 * sizeof(int));
*(p + 1) = 3;
printf("%d\n", *(p + 1));
printf("%#x\n", p + 1);
//释放堆内存
free(p);
printf("%d\n", *(p + 1));
printf("%#x\n", p + 1);
system("pause");
}
15.学号管理系统
#include <stdio.h>
#include <stdlib.h>
main(){
printf("请输入班级人数:");
int count;
scanf("%d", &count);
int i;
//申请堆内存保存学生学号
int* p = malloc(count * sizeof(int));
for(i = 1; i <= count; i++){
printf("请输入第%d个学生的学号:", i);
scanf("%d", (p + i - 1));
}
printf("请输入插班生人数:");
int newCount;
scanf("%d", &newCount);
//重新申请堆内存
//在旧的堆内存后面扩展新的空间
//如果旧的堆内存后面空间都被占用了,那么就无法扩展
//系统会另觅他处,寻觅一个足够大的堆内存区域重新申请
//并且会把旧堆内存的数据拷贝至新的堆内存
//最后释放旧的堆内存
p = realloc(p, (count + newCount) * sizeof(int));
//输入插班生学号
for(i = count + 1; i <= count + newCount; i++){
printf("请输入第%d个学生的学号:", i);
scanf("%d", (p + i - 1));
}
for(i = 1; i <= count + newCount; i++){
printf("第%d个学生的学号为%d\n", i, *(p + i - 1));
}
system("pause");
}
16.多级指针
#include <stdio.h>
#include <stdlib.h>
main(){
int i = 3;
int* p = &i;
int** q = &p;
int*** l = &q;
printf("%d\n", &i);
printf("%d\n", **q);
printf("%d\n", ***l);
system("pause");
}
17.结构体
#include <stdio.h>
#include <stdlib.h>
void study(){
printf("熊大和光头鹏解锁了一个新姿势\n");
}
//结构体中不能定义函数,但是可以定义函数指针
struct student{
int age;
int height;
char sex;
void(*studyp)();
};
int main(){
struct student stu = {20, 190, 'f', study};
printf("%d\n", stu.age);
//为了方便位移运算,结构体中各个属性的长度会被自动补齐
printf("%d\n", sizeof(stu));
//调用函数指针
stu.studyp();
struct student* stup = &stu;
(*stup).studyp();
//引用这个指针指向的结构体的属性
stup->studyp();
system("pause");
}
18.联合体
#include <stdio.h>
#include <stdlib.h>
main(){
//联合体能表示这几种变量
union{int i; short s; char c} un;
//联合体同时只能赋一个值,新值会覆盖旧值
//所以长度取决于最长的变量
un.i = 30;
un.s = 20;
printf("%d\n", un.i);
printf("%d\n", sizeof(un));
system("pause");
}
19.枚举
#include <stdio.h>
#include <stdlib.h>
enum WeekDay
{
Monday = 10,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday
};
int main(void)
{
//int day;
//枚举作用:规定了变量的取值范围
enum WeekDay day = Thursday;
printf("%d\n",day);
system("pause");
return 0;
}
20.自定义类型
#include <stdio.h>
#include <stdlib.h>
typedef int haha;
main(){
haha i = 3;
printf("%d\n", i);
system("pause");
}
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