我正在尝试在 Vscode 上执行此代码，但每当我运行此代码时，它不会获取字符的值，而只是显示一个随机数

Question

I'm new to coding and learning C++ online but while running this code it just doesn't takes the value of the character. If using cin or cout it's working fine but scanf is giving me problems. Can someone explain me what am I doing wrong in the most basic way possible

    #include<iostream>
    #include<cstdio>
    #int main(){

    int num1, num2;
    char oper;

    printf("The first number is: ");
    scanf("%d", &num1);
    printf("The second number is: ");
    scanf("%d", &num2);
    printf("The operation you want to perform is: ");
    scanf("%c", &oper);

    if(oper == '+'){
        int total= num1+num2;
        printf("%i", &total);
    }

    else if(oper == '*'){
        int mul= num1 * num2;
        printf("%d", &mul);
    }

    else{
        int diff = num1-num2;
        printf("%d", &diff);
    }

    return 0;
}

Answer 1

• You have an extra # before int main() .
• %d leaves newline character after the number read and %c will read it if it is there. You should add a space character befoer %c to have scanf() whitespace characters (including newline character) to have it ignore space characters.
• %i and %d in printf() expects int . Passing int* there invokes undefined behavior .

Fixed code:

#include<iostream>
#include<cstdio>
int main(){ // remove extra #

    int num1, num2;
    char oper;

    printf("The first number is: ");
    scanf("%d", &num1);
    printf("The second number is: ");
    scanf("%d", &num2);
    printf("The operation you want to perform is: ");
    scanf(" %c", &oper); // add a space

    if(oper == '+'){
        int total= num1+num2;
        printf("%i", total); // pass the number itself, not a pointer
    }

    else if(oper == '*'){
        int mul= num1 * num2;
        printf("%d", mul); // pass the number itself, not a pointer
    }

    else{
        int diff = num1-num2;
        printf("%d", diff); // pass the number itself, not a pointer
    }

    return 0;
}

Also your code will be better if you add some code to check return values of scanf() to check if they successfully read expected things.