Im a student in 2nd year university comp sci degree, we have mostly looked at java when it came to programming but we've done a few weeks of C++ translating java to C++ mostly. Structs were never taught to us in class, but I have been doing my own reading and they seem fairly common in many sample codes I have seen. Every example code I have seen I could program with classes/objects instead, does anyone know the advantages/disadvtanges of using classes vs structs? Structs seem a little easier to code for a lot of easy examples so far, but thats about all ive noticed. but its a very new idea to me so Im sure im missing something obvious :D

In C++ Structs are exactly the same as classes, with one minor difference -
with structs default visability is public, with classes default visability is private.

One other difference that no one has meantioned and is ESSENTIAL to understanding them is that Classes have FUNCTIONS!!! (wooo! yeaaa.. (ok I love classes and functions,))

When C was made there needed to be a way to make structures with more then just the base data types (back then there's was JUST the basic data types) So they made structs. Structs contain information on stuff that need to stay together. Very useful at the time, but as time progressed people found it less useful then originally thought as you can edit it with any thing that has access to the struct and that gets confusing, as well as the fact you still had millions of functions and all of them were called about the same way.

When C++ came around they thought they needed more work to make Structs into actual objects, and thus came the ideas of private and public variables as well as functions. This allowed the structs to no longer have everyone able to access the innermost workings of it, and allowed a VERY specific ways to work with classes as objects instead of just data lumped together.

Basically If your going to use C++ and no fear of porting you can always use classes. If you want to know when to use each, Think of it as this "do I want to have anything hidden or do I want to have any specializaed functions lumped with it?" If so use a class, if you don't mind everything being public, a struct will do the same thing as a Class, though a class does allow those wonderful functions to be added on to the end.

Now you want a brain killer, look up Unions (a C object). That's an intense concept when you first read that one.

The difference between structs and classes in c++ has already been mentioned. However, in c, they cannot contain functions. Another cool thing about structs is that if you don't have any functions/constructors/etc and no dynamic variables, you can do some quick easy storage of a struct to a file. Maybe like this:



Not 100% sure if you cannot do that with a struct/class with functions in it, testing right now.

edit: Made the code actually work. :)

edit2: It seems to me that functions don't interfere with doing raw writes and reads of the struct. Very interesting, and handy.

Structs can also have functions however. As far as the language is concerned they are exactly the same apart from as someone has already said, structs have default public visibility and classes have private. Generally use structs for data only structures and classes when the structure is going to have methods.

Quote:Original post by Rebooted
Generally use structs for data only structures and classes when the structure is going to have methods.

why?
what would it be the advantage???

Yes, that's a common misunderstanding between C and C++. When C++ came about, structs were also changed into classes, just with public as default. They aren't the same structs as in C.