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Hello,
I am C,C++/VC++ developer. I wanted to know, as in every C/C++ program there is startup function main(), who calls this function. I know OS, but I want some in detail answer. Also I wanted to know how my program actually starts, means how it is loaded in memory, who loads it and etc..
Thanks in advance.
Regards
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This question can only be answered by looking at a specific OS. In general the OS starts the respective runtime which in turn calls into main after doing some initialization work. If you want to know the exact call stack for YOUR system, just hold on in the properly configured debugger at some point of the program and trace back to the roots... Use breakpoints on visible global objects with non-trivial constructors to see what's happening before the program enters main. At least on Windows you will be able to trace back the runtime-code as well.
Cheers,
Paul
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The operating system takes care of loading an executable file into memory, and then starts executing it at a specific point in the code, known as the "entry point". It has a special field in the EXE file format, which obviously gets filled by the linker from the information it got from the compiler. The entry point's name may vary, in C it normally is called main, and sometimes WinMain. In other languages it may be called differently, it is basically a convention between the programmer and the compiler.
For Windows, you can get the EXE file format specification here[^]. That will keep you busy for a while!
Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.
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Luc Pattyn wrote: The entry point's name may vary, in C it normally is called main, and sometimes WinMain.
Not quite; these are the start points for the user part of the application, and are called by the initialisation routine, which is why (Win)main() has to have a specific signature. The actual entry point of the exe is much earlier and is part of the framework library that is automatically added by the linker.
The best things in life are not things.
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You're quite right.
Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum
Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.
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The book "Linkers & Loaders" by John R. Levine is a good resource for questions involving this and similar subject matter.
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hello guys... I have this piece of code. Lets say my name contains 'u' one time, my code will reduce the string size by 1, exludes the 'u' from string and displays it on screen.
if (chr[i] == 'u'){
count++;
}
else{
cout<<chr[i];
}
cout<<"\nIt has "<<strlen(chr) - count<<" characters.";
Now I am using if - else here...can these two tasks be done in just if ? Like incrementing count and displaying name in if without using else.
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Yes:
if(chr[i] != 'u' || !++count) {
cout << chr[i];
}
Whether you should do this or not is another question - it's a lot harder to understand.
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Ummmm, definitely not advisable:
1. Whether this works or not is compiler dependend - a compiler is free to evaluate the left or right side of an || operator in whatever order it likes!
2. Like you said, hardly anyone will understand, and even those that do will doubt what it does was actially intended, and might decide to 'fix' it wrongly.
Apart from that - interesting thought; I was about to answer 'no' 
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Stefan63 wrote: 1. Whether this works or not is compiler dependend - a compiler is free to evaluate the left or right side of an || operator in whatever order it likes!
Erm... hold on a sec here... Short-circuiting IS mandated, and can only work if it's evaluated in order. It's always true for PODs.
The only caveat is, if it is a class, and that class has an overloaded && or || operator. Then, both sides will be evaluated, so that the compiler can pass the element on the right hand side as a parameter.
One (very) good reason to never, ever overload them.
At least, this is the way I understand it, and I can't imagine anything undoing that, as tons of code that did this:
if( pszString != NULL && *pszString != '\0' )
would randomly crash if *pszString was evaluated first. Course, in this example the actual comparisons can be removed, but I was trying to be explicit.
N'est pas?
-- CraigL
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I've learned not to rely on evaluation order, but I just looked it up and found my argument would only be true in cases where both argument sneed to be evaluated in any case, such as in an addition. In fact, Stroustrup explicitely names the exception, and that exception is exactly what you said:
"The operators ' (comma), && (logical and), and || (logical or) guarantee that their left-hand operand is evaluated before their right-hand operand."
(Bjarne Stroustrup, The C++ Programming Language, Third edition, page 123)
So I stand corrected.
Thanks for pointing this out.
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I think there's some piece of information missing: Your code doesn't show a loop, or any other construct that loops through the characters in chr, and there's no point in displaying count before the end of that loop. Then in your request you suggest displaying 'name' within your if block, but there's no variable name, and if this should refer to chr, there is no point in displaying it fully for every value of i that you use in that if statement.
Unless your string chr will always be exactly "u" (i. e. a string of 1 character, which is 'u'), your question, taken literally, doesn't make much sense.
Besides, why do you want to get rid of that else statement?
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How create a GUI to allow screen capture?
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You mean other than the built in windows one? Do you only want a subset of your screen captured?
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I want to implement a mechanism that allows users to easy select the capture area (the entire screen, the window of a program, a rectangle, ...)...is it possible?
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Yes it's possible.
Which part are you not sure about?
Mark Salsbery
Microsoft MVP - Visual C++
![Java | [Coffee]](https://www.codeproject.com/script/Forums/Images/coffee.gif)
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This is possible. One of the early editions of Petzold's Windows books - "Programming Windows 95" gives an example of the BitBlt() which does exactly this. This is done in raw Windows API. You can, of course, redo it in C# or your favorite language.
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yes, i know BitBlt(), but how can i get the handle of the window that mouse over?how can i select, with mouse, a rectangle of the screen?
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Member 2965471 wrote: but how can i get the handle of the window that mouse over?how can i select, with mouse, a rectangle of the screen?
This is relatively simple if you know anything about Win32 UI/graphics programming. Since you seem to want to skip that part, why not just search for examples?
Binging "win32 draw selection rectangle on desktop" finds many examples, including this...
Screen Capture (Simple Win32 Dialog Based)[^]
Mark Salsbery
Microsoft MVP - Visual C++
modified on Saturday, May 14, 2011 12:44 PM
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Hi
Does anyone know how to get/use the red squiggly line used in Ms word for spelling mistakes
thanks
simon
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This is not the proper forum for this question... this is "Forum: C / C++ / MFC"
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How do you know the OP is not asking about how to implement spell check in CRichEditCtrl?
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How does anyone know...
Mark Salsbery
Microsoft MVP - Visual C++
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