在 C++ 中编程 If else 语句

Question

I was writing a c++ code but it returns error. I have just started c++ and i don't know how to rectify it this is the error :

tempCodeRunnerFile.cpp:5:1: error: '::main' must return 'int'
     5 | void main()
       | ^~~~
tempCodeRunnerFile.cpp: In function 'int main()':
tempCodeRunnerFile.cpp:8:5: error: 'clrscr' was not declared in this scope
    8 |     clrscr();
      |   

this is my code: I want to input two numbers and return "Variable one is greater" if first variable is greater and if second is greater then "second variable is greater"

#include<iostream>
#include<conio.h>
using namespace std;

void main()
{

    clrscr();
    int vari,vari2;

    cout<<"Enter a Variable: ";
    cin>>vari;
    cout<<"Enter Another Variable: ";    
    cin>>vari2;

    if (vari>vari2){
        cout<<"Variable 1 was greater";
    }
    else if (vari=vari2)
    {
        cout<<"Variables Are Equal"; 
    }
    else
    {
        cout<<"Variable 2 is Greater";
    }



    getch();
}

Answer 1

clrscr() is an obsolete function that clears the console screen that was used in some old Borland Turbo C++ compilers. Your program should work also without it, so you can delete it.

There's another error, though:

else if (vari=vari2)

This does not do comparison between those variables, instead it assigns vari2 to vari1. Fix it like this:

else if (vari==vari2)

Answer 2

vari=vari2 is an assignment, and it's value is actualy the value of vari after the assignment, converted to bool.

The statement should be vari == vari2

Answer 3

Before going to answer any of your error, I would like to know if you were running the code in VS code for only a selective statements? Because the tempCodeRunnerFile.cpp file only generates in VS code when you run a specific section of code instead of whole code file using Code Runner extension. So that may be your first problem.

Let's solve your errors now. The first error error: '::main' must return 'int' 5 | void main() | ^~~~ error: '::main' must return 'int' 5 | void main() | ^~~~ error: '::main' must return 'int' 5 | void main() | ^~~~ shows the main function must return an integer value for your code. So instead of using void main() use int main() . Don't forget to add return 0; statement at the end. Your first error is solved now.

About your second error, I don't have any clear answer but if I guess it's due to using clrscr() . As much I know , clrscr is a Borland TurboC++ non-standard function(very old), and isn't present in other compilers, so it's may be due to that. To clear the screen in modern compilers use the system("cls"); code which is a part of stdlib.h header file. (NOTE: use #include<stdlib.h> in beginning)

Apart these errors another thing wrong with your code is that you used vari=vari2 which is not done for equality check. So do vari==vari2 .

That's all I know.