joel wrote:
Dates in excel are stored a a single precision number 24 bit IEEE
standard and uses 4 bytes (32bits) to store the data. Integers were 16
bits (2 byes) but I'm told they are being stored as long which is also
32 bit.

including time in it, date is stored as double.
and there is no way to distinguish if number passed to c++ procedure is
a real double or a date.
That what i was asking for. if there is really no way to distinguish
that or simply I don't know how to do that.

and procedure to convert number into date and date into number is simple
but requires a little of bit o work. That procedure is of course
included in Excel but not available as "source code", so I was asking if
that information is somewhere so I don't have to write what is already
written.

We are at the beginning.




Characters are 1 byte (8 bit) per character but I believe the
actual storage of the string has the byte count before the actual data

yes.

(I don't think you actually see the byte count when it is passed to
another function).


strings are passed as pointers and must be prepared the same way in
XLOPER. First byte represents string length.