例3-8+3-9

#include<stdio.h>
int main(void)
{
    int choice,i;
    double price;

    for(i=1;i<=5;i++){
        printf("[1]Select crisps
");
        printf("[2]Select popcorn
");
        printf("[3]Select chocolate
");
        printf("[4]Select cola
");
        printf("[0]exit
");

        printf("Enter choice:");
        scanf("%d",&choice);

        if(choice==0)
            break;

        switch(choice){
            case 1:price=3.0;break;
            case 2:price=2.5;break;
            case 3:price=4.0;break;
            case 4:price=3.5;break;
            default:price=0.0;break;
        }
        printf("price=%0.1f
",price);
    }
    printf("Thanks
");

    return 0;
}

#include<stdio.h>
int main(void)
{
    double value1,value2;
    char op;

    printf("Type in an  expression:");
    scanf("%lf%c%lf",&value1,&op,&value2);
    switch(op){
    case'+':
        printf("=%.2f
",value1+value2);
        break;
    case'-':
        printf("=%.2f
",value1-value2);
        break;
    case'*':
        printf("=%.2f
",value1*value2);
        break;
    case'/':
        printf("=%.2f
",value1/value2);
        break;
    default:
        printf("Unknown operator
");
        break;
    }
    return 0;
}