This little structure is useful for communicating version information.
Amongst things, it is used to check the client and the server versions are compatible as well as being used as part of the sis installer versioning

Now what will the following print?

const TVersion ver(192,278,20070403);
RDebug::Printf(_L("%d.%d.%d"), ver.iMajor, ver.iMinor, ver.iBuild);

Well the result is "-64.22.16387" but why does this happen?

Lets look at the class declaration:

class TVersion
    {
public:
    IMPORT_C TVersion();
    IMPORT_C TVersion(TInt aMajor,TInt aMinor,TInt aBuild);
    IMPORT_C TVersionName Name() const;
public:
    TInt8 iMajor;
    TInt8 iMinor;
    TInt16 iBuild;
    };

 The fields are stored as 1 and 2 byte values but the constructor takes an int. So if you have version number that is greater than 255 or a build number greater than 32767 the compiler will silently truncate the value down to a smaller value.

Whilst this is annoying, in the FP2 SDK, the makesis code checks the ranges and maks sure they will fit, if the don't then the makesis program exists without building a sis file.

So beware, in at least FP2 make sure your build numbers fit inside a version structure!