What is a structure and how is it different from a class?

What languages use structures/classes?

And in what are some of the postitive and negative effects of them? (in the areas of readability, concept understanding, code optomization - written and compiled - etc.)

Thanks guys!

typically a structure is a plain structure, meaning a group of structure data, and resides in memory. a structure Does not have any code.. while a class contains Code and Data, also a structure is typically static, once it is defined it is defined, and does not change (however certian language support structures, that you subparts of it can represent different data.)
A class has features such as inheritance, and thus different children can add, overide both the data and the code, a structure is static, and doesn't have inheritance..

However in C#, a structure can have code in it

most object orientated languages would have both structures and classes such as C++,Delphi, C#, java and pigsnose, VB.net

Most older languages still have structures, even a good assembler has structures.. so basic, c, pascal, mostly anything.

Karl

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Karl /GODCENTRIC
Visionary Media
the creative submitted to the divine.
Husband of my amazing wife Aleshia
Klumsy@xtra.co.nz

Also, structures hold only variables but cant those be changed? and arnt classes basically structures with functions/methods?

and also there is no code..
but i class could have code like 'validatestate' or zip, maybe add field - like country, or add a class that can deal with canadian addresses etc.

but in a sense a class is a structure with code added, but more features..
you can simulate a class say in standard C with a structure, with some of the structures members being function pointers or such.

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Karl /GODCENTRIC
Visionary Media
the creative submitted to the divine.
Husband of my amazing wife Aleshia
Klumsy@xtra.co.nz

What about the negative aspects (other than structures being static?)

struct MyStruct { int a; // a is *public* private: int b: // b is private public: int c; // c is public }; class MyClass { int a; // a is *private* private: int b; // b is private public int c; // c is public };

In C++, that's the ONLY difference. If you don't explicity create constructors/destructors for your classes and structs, the compiler will create them for you anyway. Note this is only for C++. In C, there are no classes, and structs cannot have member functions including constructors/destructors. As such, for simply historic/habit reasons, people generally don't put member functions in structs, and use classes when they want member functions. But the language allows you to treat structs and classes identically. This struct and this class are both completely valid and completely identical:

struct MyStruct { private: int a, b, c; protected: float x, y, z; float total; public: MyStruct(); // default constructor MyStruct(int init_a, int init_b, int init_c); // initializing constuctor void SetValues(float set_x, float set_y, float set_z); inline float GetTotal() { total = x+y+z; return total; }; }; struct MyClass { private: int a, b, c; protected: float x, y, z; float total; public: MyClass(); // default constructor MyClass(int init_a, int init_b, int init_c); // initializing constuctor void SetValues(float set_x, float set_y, float set_z); inline float GetTotal() { total = x+y+z; return total; }; };

There's really no downside to using structs/classes. The only thing I can think of is that you should be aware that in C++, if you don't explicity declare constructors/destructors, the compiler adds them anyway. This, along with alignment settings for the compiler, may result in their sizes and addresses (in an array or whatever) not being obvious (i.e. don't assume/hardcode sizes or addresses, which you shouldn't do anyway).

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Brian