例3-5+3-7

#include<stdio.h>
int main(void)
{
    double value1,value2;
    char op;
    printf("Type in an eapression:");
    scanf("%lf%c%lf",&value1,&op,&value2);

    if(op=='+')
        printf("=%.2f\n",value1+value2);
    else if(op=='-')
        printf("=%.2f\n",value1-value2);
    else if(op=='*')
        printf("=%.2f\n",value1*value2);
    else if(op=='/')
        printf("=%.2f\n",value1/value2);
    else
        printf("Unknown operator\n");

    return 0;
}

#include<stdio.h>
int main(void)
{
    int digit,letter,other;
    char ch;
    int i;
    digit=letter=other=0;
    printf("Enter 10 characters:");
    for(i=1;i<=10;i++){
        ch=getchar();
        if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z'))
            letter++;
        else if(ch>='0'&&ch<='9')
            digit++;
        else
            other++;
    }
    printf("letter=%d,digit=%d,other=%d\n",letter,digit,other);

    return 0;
}