[fitsbits] FITS Format

[Acrobat]

Hello I have a problem to write a program in Visual Basic to read a fits
file.
For the header section there are no problem but for the data there a problem
In the file header  I find a card with the keyword : BITSWAP that it is not
documented in any my documentation that I found in the web.
Any idea on this keyword ?

Do you know a librarry that I can use with my Visual Basic program ?

Thank you

Luigi Azario