QuickBasic BSAVE Header format.

The total length of the header is 7 bytes.

Byte 1   IdByte     This must evaluate to &HFD to be a valid BSAVE file.
In QuickBasic use ASC function of a 1 character string variable. 

Byte 2-3 Segment

Byte 4-5 Address

Byte 6-7 Length     Useful if you wish to dimension an array ahead of
time to hold the BLOAD.