what is(int main(int argc, char argv[]) ) means?

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hi
what is this line means :

C++

int main(int argc, char argv[])

and what does it does?

and too this:

C++

int _tmain(int argc, _TCHAR* argv[])

and what is the difference between those and follows :

C++

int main ()

please explain it simply

thanks

Posted 9-Feb-13 7:47am

hor_313

Updated 9-Feb-13 7:50am

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Philippe Mori 2-Apr-13 13:09pm

You should read the documentation...

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skydger · Answer 1 · 2013-02-09T08:14:00

Solution 2

C++

int main(int argc, char *argv[])
int main ()

These are the entry points of any program according to C++ standard. The first is with the command line parameters, second is without them.

C++

int _tmain(int argc, _TCHAR* argv[])

This is Microsoft's extension to C++ standard entry point. It made for multibyte and unicode strings compatibility.

upd.
About main in ISO C++ standard 3.6.1
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1905.pdf[^]
Please see page 51

Posted 9-Feb-13 8:14am

skydger

Updated 10-Feb-13 3:41am

v2

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hor_313 10-Feb-13 4:46am

i remember when i was learning c++ we use some forms like this :

int main(int a , int b )

what is the difference between this form and that form i written in topic?
still i cant underestand what do the bracketed phrases do?

skydger 10-Feb-13 9:53am

Either you was learning a different language or it was a misprint. :) Non of entry point functions has such notation. C++ standard specifies only two of them mentioned in all solutions for your question. I updated this solution with link to ISO C++ standard.

As for 'bracketed phrases'... If you meant char* argv[] then see the complete Solution 1. Well... if you never faced programs with cpmmand-line parameters, then I understand your confusion. Please see this article, maybe it will make it clear for you:
http://en.wikipedia.org/wiki/Command-line_interface

hor_313 10-Feb-13 11:49am

yes i didnt work by command line and i dont know about how it works

skydger 10-Feb-13 12:36pm

Ok, it explains your confusion. So you may achieve this by launching Command Prompt (cmd.exe) in MS Windows (or launch a console in Linux). Then you should execute your program like "myapp.exe -hello -world". "-hello" and "-world" will be in char *argv[] array.
There is another way to do this. In Visual Studio in your executable project's poperties window go to Debuging section, then write down your "Command arguments" which will appear at the start of you app.

hor_313 11-Feb-13 3:58am

thanks a lot

Sergey Alexandrovich Kryukov 2-Apr-13 1:55am

My 5.
—SA

skydger 3-Apr-13 13:19pm

Thank you :)

Sergey Alexandrovich Kryukov · Answer 2 · 2013-02-09T08:05:00

A user can run your program with command-line parameters, for example:

youApplication.exe param1 -i filename.txt /verbose

In this example, the user passes the parameters "param1", "-i", "filename.txt" and "/verbose". That they mean is totally defined by your application.

You can access these parameters via the arguments of main you show. First parameter gives you the number of command line parameters, and the second one, array of strings, gives you the parameter values.

It's your business to interpret them and use as the user input.

[EDIT]

Please see: http://en.wikipedia.org/wiki/Main_function#C_and_C.2B.2B[^].

—SA

H.Brydon · Answer 3 · 2013-02-09T08:27:00

C++ as a language is derived from C, which was originally a console based language. The api "main()" (with or without parameters) is the entry point to your program. If you do not provide parameters, the api is called and your program is not able to see any parameters that may have been passed to the program.

Moving along a few decades now, Microsoft Windows supports ANSI and UNICODE. The API _tmain is a macro that expand to the program entry point main (ANSI) or wmain (UNICODE) according to _UNICODE macro. Starting with VC2005 (?), a program that is UNICODE enabled (ie. _UNICODE defined) will expand _tmain to wmain (not main) and _TCHAR expands to wchar_t.

The Microsoft explanation can be found here[^]. Beware that they have some square brackets in the text that are confusing and can be misinterpreted.

Usman Hunjra · Answer 4 · 2013-02-10T05:22:00

Hey.. I think you are student too. However my teacher says that simply remove this

C++

int _tmain(int argc, _TCHAR* argv[])

and write a main like this:

C++

int main()

because at that level we are now, we should not consider that.!!
Moreover you write

C++

int main(int a, int b)

it will work but, that is wrong actually this concept is called functions, main is also a function but in main we call the other function and the int a, int b are called parameters.
You should write main as:
C++

int main()

REMEMBER: EVERYTHING COMES TO YOU AT RIGHT TIME. . .

what is(int main(int argc, char argv[]) ) means?

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