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In C, are arrays pointers or used as pointers?
In C++, the default main function can have arguments like char* argv[]. What is the its difference from char** and char* argv[100] ?
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There is no difference in function parameters. In other situations, the first declares a pointer, the second declares an array.
Dirk Holsopple
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There is a difference. In `char* [100]` you have some more information. – J.N. Oct 22 '12 at 13:20
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@J.N. Not in function parameters. In function parameters, if the rightmost type is an array, the size is ignored. – Dirk Holsopple Oct 22 '12 at 13:24
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@J.N. There's no difference between the two declarations when they appear in function declaration. – jrok Oct 22 '12 at 13:24
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Indeed, I was wrong, though it would be useful to disambiguate. The difference only applies for array references. – J.N. Oct 22 '12 at 13:28
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char** is a pointer to a pointer to a char.
The second char *argv[100] is an array of pointers to a char.
But when you pass an array to functions they decay to a pointer.
Lews Therin
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Decay? like zombies decay and become decrepit and begin losing body parts? – Richard Chambers Oct 22 '12 at 13:23
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Ha ha this isn't The Walking Dead :) That is just the terminology used. – Lews Therin Oct 22 '12 at 13:25
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Well, if you use C-arrays and `char*` in C++, you are mentally a zombie. – daknøk Oct 22 '12 at 13:25
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@RichardChambers See [this explanation](http://stackoverflow.com/a/4607149/478288). – chrisaycock Oct 22 '12 at 13:25
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2@daknøk, personally I think throwing a bit of C into C++ adds flavor and vitamins with a touch of job security as well! And what is this bit about having to do a head shot to kill a zombie if they have no brains? – Richard Chambers Oct 22 '12 at 13:30
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I’d never hire a C++ programmer that uses C-arrays instead of `std::vector` or `std::array`. – daknøk Oct 22 '12 at 13:32
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char** argv: To elicit the same behavior as char* argv[100] you must dynamically allocate space to store char pointers. For example: (*argv) = new char[100];
Double pointers are a very flexible datatype unique to C++ which can grant insane speed and insane bugs. Generally if you know the size of your array, its best to avoid dynamic memory allocation.
Steve Barna
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1They are not unique to C++ ;). You can have them in C and Pascal for instance. – J.N. Oct 22 '12 at 13:33
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I think this was a joke post and not meant to be taken seriously. – Richard Chambers Oct 22 '12 at 13:34
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Argh I think it's time to go to bed, I stopped at the first part of the sentence. – J.N. Oct 22 '12 at 13:35
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