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C++ question

JeraldtheBEAR · 2020-12-23T15:29:58

This is a very basic question. In int main() why is it a int and not a void and why do you have to return 0. #include <iostream> // The # represens a preprocessor directive and <iostream is a header file> int main() { //std stands for standard std::cout << "You are a secret agent breaking into a secure server room..."; std::cout << std::endl; //endl means end line std::cout << "You need to enter the correct codes to continue..."; const int a = 4; const int b = 3; const int c = 2; const int sum = a + b + c; const int product = a * b * c; std::cout << std::endl; std::cout << sum << std::endl; std::cout << product << std::endl; return 0; //use std::cout << std::endl for new line } Don't mind the comments. I am taking a udemy class and it says you have to return 0. Why did they say that. Thanks for the help.

For Beginners question

Started by JeraldtheBEAR June 12, 2020 11:36 PM

16 comments, last by fleabay 3 years, 5 months ago

8Observer8

395

June 16, 2020 07:43 AM

It is difficult to remember what you must to return 0 or 1. Return EXIT_SUCCESS or EXIT_FAILURE. This macros contains 0 and 1 respectively.

#include <iostream>

int main()
{
    std::cout << "Hello World!" << std::endl;

    bool isError = false;
    if (isError)
    {
        std::cerr << "Error message" << std::endl;
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}

8Observer8

395

June 16, 2020 07:50 AM

I think it is right for Qt console application, isn't it?

#include <QCoreApplication>
#include <iostream>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    std::cout << "Hello World!" << std::endl;

    bool isError = true;
    if (isError)
    {
        std::cerr << "Error message" << std::endl;
        return EXIT_FAILURE;
    }

    return a.exec();
}

Switchboy

June 17, 2020 01:36 PM

In DOS the return value can be used to let the system or other batch scipts know that the program completed succesfully or encounterd an error. You or someone else can use this to handle acordingly:

See for reference:
https://www.tutorialspoint.com/batch_script/batch_script_return_code.htm

None

Alberth

10,216

December 23, 2020 08:14 AM

Bazzy_505 said:
void myAwesmeFunction() { // your code };

Please be careful here. This is not a complete function, as the closing curly bracket is comment text. Either use 2 lines, or a block comment like

void may_awesome_function() { /* your code */ }; // C++ typically doesn't use camelcase for functions.

Alberth

10,216

December 23, 2020 08:20 AM

Prototype said:
There even was a YESNO.COM that would ask for user input and more of that. It was more or less an attempt at modular programming.

I think they tried to simulate a Unix shell, except it failed horribly as the COMMAND program was too weak compared to a Unix shell, and lack of multi-tasking pretty much broke any attempt to use pipes.