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Questions tagged [program-entry-point]

Use this tag for questions about entry points to executables (programs); e.g., the "main()" function in most programming languages. If your question is programming language specific, tag that: language as well e.g. C, C++, Java etc.

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What does if __name__ == "__main__": do?

What does this do, and why should one include the if statement? if __name__ == "__main__": print("Hello, World!") If you are trying to close a question where someone should be using this idiom and isn't, consider closing as a duplicate of Why…
Devoted
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What does "Could not find or load main class" mean?

A common problem that new Java developers experience is that their programs fail to run with the error message: Could not find or load main class ... What does this mean, what causes it, and how should you fix it?
Stephen C
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Can't execute jar- file: "no main manifest attribute"

I have installed an application and when I try to run it (it's an executable jar) nothing happens. When I run it from the command line with: java -jar "app.jar" I get the following message: no main manifest attribute, in "app.jar" Normally, if I…
Ewoud
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What should main() return in C and C++?

What is the correct (most efficient) way to define the main() function in C and C++ — int main() or void main() — and why? And how about the arguments? If int main() then return 1 or return 0? There are numerous duplicates of this question,…
Joel
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Why is the Java main method static?

The method signature of a Java mainmethod is: public static void main(String[] args) { ... } Is there a reason why this method must be static?
Alotor
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What is the "String args[]" parameter in the main method?

What does the following Java code mean? public static void main(String[] args) What is String[] args? When would you use these args? Source code and/or examples are preferred over abstract explanations.
freddiefujiwara
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Is main a valid Java identifier?

One of my kids is taking Java in high school and had this on one of his tests: Which of the following is a valid identifier in Java? a. 123java b. main c. java1234 d. {abce e. )whoot He answered b and got it wrong. I looked at the question…
Gary Bak
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Should I return EXIT_SUCCESS or 0 from main()?

It's a simple question, but I keep seeing conflicting answers: should the main routine of a C++ program return 0 or EXIT_SUCCESS? #include int main(){return EXIT_SUCCESS;} or int main(){return 0;} Are they the exact same thing? Should…
Trevor Hickey
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What is the proper declaration of main in C++?

Questions What is the proper signature of the main function in C++? What is the correct return type, and what does it mean to return a value from main? What are the allowed parameter types, and what are their meanings? Is this…
fredoverflow
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No Main() in WPF?

I am a beginner when it comes to programming but I was sure that one of the universal rules was that a program starts with Main(). I do not see one when I create a WPF project. Is Main() simply named something differently in WPF?
Juice
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"int main (vooid)"? How does that work?

I recently had to type in a small C test program and, in the process, I made a spelling mistake in the main function by accidentally using vooid instead of void. And yet it still worked. Reducing it down to its smallest complete version, I ended up…
paxdiablo
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Is main() really start of a C++ program?

The section $3.6.1/1 from the C++ Standard reads, A program shall contain a global function called main, which is the designated start of the program. Now consider this code, int square(int i) { return i*i; } int user_main() { for ( int i = 0…
Nawaz
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In Python, can I call the main() of an imported module?

In Python I have a module myModule.py where I define a few functions and a main(), which takes a few command line arguments. I usually call this main() from a bash script. Now, I would like to put everything into a small package, so I thought that…
Ricky Robinson
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Why do we need argc while there is always a null at the end of argv?

It seems that the argv[argc] is always NULL, so I think we can traverse the argument list without argc. A single while loop will do this. If there is always a NULL at the end of argv, why do we need an argc?
StarPinkER
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Why main does not return 0 here?

I was just reading ISO/IEC 9899:201x Committee Draft — April 12, 2011 in which i found under 5.1.2.2.3 Program termination ..reaching the } that terminates the main function returns a value of 0. it means if you don't specify any return…
Jeegar Patel
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