Packed Decimal (but NOT Comp-3)

Question

I'm encountering a series of numeric fields in this data file. The fields are 6-bytes (12-nibbles)

The first nibble - in all cases so far, is "4" The second nibble represents the number of digits to the LEFT of the decimal point. The remaining nibbles are the value of the field.

So - for example, 4327 0000 0000 = 270.0 and, 4260 0000 0000 = 60.0 and, 4026 3000 0000 = 0.263

My questions are: Is the "4" significant? (How/why?)

Is there a possibility that this first nibble also contains the sign bit? (All of the examples I currently have are positive values - so I have no frame of reference.)

If this were a longer field - say one with 16 nibbles - would it be possible that the digit-left-of-decimal value would be higher than 9 - and how would that be represented? (Second nibble as 'A'/'B'/etc or increment the first nibble so that it's shows '5'?

Has anyone seen this particular pattern - and know what's going on?

(I do not know the programming language used to create the file.)

Answer 1

I think 4 is a type nibble. The type indicates how to interpret the rest of the nibbles.