//简单的屏幕输出
#include <stdio.h>
void main(){
int a = 1;
float b = 2.5;

char c = 'C';

printf("a=%d\n",a);
printf("b=%.2f\n",b);
printf("c=%c\n",c);
}

//计算显示数据类型所占空间的大小
#include <stdio.h>
void main(){
int a = 1;
float b = 2.5;

printf("%d\n",sizeof(a));
printf("%f\n",sizeof(b));
printf("%d\n",sizeof(int));
printf("%d\n",sizeof(float));
}

//计算三位整数的个位十位百位数字之和
void main(){
int x = 135;
int b0,b1,b2;
int sum;

b0 = x / 100; //百位
b1 = (x - b0*100)/10 ; //十位
b2 = x % 10 ; //个位

sum = b0 + b1 + b2;

printf("b0=%d\n",b0);
printf("b1=%d\n",b1);
printf("b2=%d\n",b2);
printf("sum=%d\n",sum);
}
//自增运算符
void main(){
int n = 3;
m = n++;

printf("n=%d\n",n);
printf("m=%d\n",m);
}

//const常量
void main(){
const double PI = 3.1; //const常量可以定义数据类型
// #define PI 3.1; 宏常量不可以定义数据类型
int r;

printf("Input r:");
scanf("%d",&r);
printf("r=%d\n",r);
printf("circumfrence=%.2f\n",2*PI*r);
printf("area=%f\n",PI*r*r);
}

//大写字母转换小写，并输出其ASCII码
void main(){
char ch;
printf("press a key and press enter :");
scanf("%c",&ch);
//ch = getChar();
ch = ch + 32; //小写字母比大写的码值大32；
printf("%c,%d\n",ch,ch);
}

//scanf("%c")的细节,%c格式说明符的细节,%c会读取空格回车制表符
void main(){
int a ;
char b;
float c;
//tips:如果在输入字符的过程中按下回车键程序运行结束，所以需要将回车键作为字符读取出来
//输入整型
printf("please input an integer:");
scanf("%d",&a);
printf("Integer:%d\n",a);
//输入字符
printf("please input a character:");
scanf(" %c",&b);
printf("Character:%c\n",b);
//输入浮点型
printf("please input a float number:");
scanf("%f,&c");
printf("float number:%.2f\n",c);
}

//scanf("%d%d")中,两个%d中间的字符在程序运行时必须按原样输入，否则出现错误
//忽略输入修饰符*,输入的任意值都不会赋值
main(){
int a,b;
scanf("%d%*c%d",&a,&b);
printf("a=%d,n=%d\n",a,b);
}