实验2

//ex1.cpp
#include <stdio.h>
int main() {
    int a = 5, b = 7, c = 100, d, e, f;
    d = a / b * c;
    e = a * c / b;
    f = c / b * a;
    printf("d=%d,e=%d,f=%d\n", d, e, f);

    return 0;
}
回答：ac/b ac/b ac/b
        原因是 c语言中的除法运算结果是取整型

//ex2.cpp
#include<stdio.h>
int main() {
    int x = 1234;
    float f = 123.456;
    double m = 123.456;
    char ch = 'a';
    char a[] = "Hello,world!";
    int y = 3, z = 4;

    printf("%d %d\n", y, z);
    printf("y=%d,z=%d\n", y, z);
    printf("%8d,%2d\n", x, x);
    printf("%f,%8f,%8.1f,%.2e\n", f, f, f, f, f);
    printf("%lf\n", m);
    printf("%3c\n", ch);
    printf("%s\n%15s\n%10.5s\n%2.5s\n%.3s\n", a, a, a, a, a);

    return 0;

//ex3.cpp
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main() {
    double x, y;
    char c1, c2, c3;
    int a1, a2, a3;

    scanf("%d%d%d", &a1, &a2, &a3);
    printf("%d,%d,%d\n", a1, a2, a3);
    scanf("%c%c%c", &c1, &c2, &c3);
    printf("%c%c%c\n", c1, c2, c3);
    scanf("%lf,%lf", &x, &y);
    printf("%.1lf,%.1lf\n", x, y);

    return 0;

}

//ex4.cpp
//判断字符类型
#include <stdio.h>
int main() {
    char x;
    x = getchar();
    if (x >= '0' && x <= '9') {
        printf("%c是数字字符\n", x);
    }
    else if (x>=65&& x <=122){
        printf("%c是英文字母\n", x);
    }
    else {
        printf("%c是其它字符\n", x);
    }
    return 0;
}

//ex5.cpp
#include <stdio.h>
int main() {
    char ans1, ans2;
    printf("复习了没？(输入y或Y表示复习了，输入n或N表示没有复习）：");
    ans1 = getchar();
    getchar();
    printf("\n动手敲代码了没？（输入y或Y表示复习了，输入n或N表示没有复习）：");
    ans2 = getchar();
    getchar();
    if ((ans1=='y'&&ans2=='y')||(ans1=='Y'&&ans2=='Y')||(ans1=='Y'&&ans2=='y')||(ans2=='Y'&ans1=='y'))
        printf("\n罗马不是一天建成的:)");
    else
        printf("\n罗马不是一天毁掉的:(");
    return 0;

}


//ex6.cpp
#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <math.h>
int main() {
    int n, sum;
    scanf("%d", &n);
    sum = (1 - pow(2, n)) / (1 - 2);
    printf("n=%d时,sum=%d", n,sum);
    return 0;

}