size of a class with no member

[saby]

Can anybody tell me why the sizeof() operation on a class having no member gives a size of 1 byte.

Thanks,

[DeMan]

because it exists

[saby]

When I take sizeof() of a class having one integer member, that comes out as 4 bytes, but not 4+1 or 5 bytes. since integer is of 4 bytes, and a blank class of 1 byte.

Can I get some explaination please.

[willakawill]

When I take sizeof() of a class having one integer member, that comes out as 4 bytes, but not 4+1 or 5 bytes. since integer is of 4 bytes, and a blank class of 1 byte.

Can I get some explaination please.

You might like to read this article

[thefarmer]

Can anybody tell me why the sizeof() operation on a class having no member gives a size of 1 byte.

Thanks,

hi there,

sizeof()
This operator accepts one parameter, which can be either a type or a variable itself and returns the size in bytes of that type or object:

a = sizeof (char);

This will assign the value 1 to a because char is a one-byte long type.
The value returned by sizeof is a constant, so it is always determined before program execution.

i hope this helps you alot

regards,

[horace1]

Can anybody tell me why the sizeof() operation on a class having no member gives a size of 1 byte.

Thanks,

see the discussion on
http://www.velocityreviews.com/forums/t279653-sizeofobject-is-different-in-ansi-and-unicode.html

[Banfa]

If you can be bothered to read the links basically a class or structure must have size, if it did not have size then in and array of such structures every entry would have the same address and the standards specifically prohibit this.

Therefore to meet the standards the compiler will assign a structure or class with no members a size of 1 so that each is guaranteed to have a different memory address to any other variable or structure. This byte is not used for anything so if a structure has data members it is not added as that would just waste space.

Note not all compilers act in the same way in relation to this problem.

[saby]

Thanx a ton Banfa. Ur explanation is really very practical.

If you can be bothered to read the links basically a class or structure must have size, if it did not have size then in and array of such structures every entry would have the same address and the standards specifically prohibit this.

Therefore to meet the standards the compiler will assign a structure or class with no members a size of 1 so that each is guaranteed to have a different memory address to any other variable or structure. This byte is not used for anything so if a structure has data members it is not added as that would just waste space.

Note not all compilers act in the same way in relation to this problem.