main() in C, C++, Java, C#

Question

Is main() (or Main()) in C, C++, Java or C#, a user-defined function or a built-in function?

Answer 1

Quote from the C Standard (emphasis is mine):

5.1.2.1 Freestanding environment

1. In a freestanding environment (in which C program execution may take place without any benefit of an operating system), the name and type of the function called at program startup are implementation-defined. Any library facilities available to a freestanding program, other than the minimal set required by clause 4, are implementation-defined.

main(), in a freestanding environment, is very much a user-defined function.

Answer 2

It's a user-defined function that is necessary for a program to execute. When you go to run your program in the compiled language, the main function is what is executed. For instance, in Java, if you have a function of the signature public static void main(String ... args) in a class then that class can be executed, as the JVM will execute the contents of that main method.

Example in Java:

public class Test {
  public static void main(String ... args) { 
    System.out.println("Hello World");
  }
}

...

javac Test.java

...

java Test

Results in "Hello World" being printed to the console.

Answer 3

In C/C++, it a standard so its built in and reconized.

Java, not sure, no experience

C# - Its a part of a class so its defined by you.

All of these are defined by you -- you tell it what to do.