[Gambas-user] "write byte[]" question

[wally]

I have a question how data is written to file.
for example:
arrObject_3 contains the capital ABC........... a.s.o

then doing:
 Write #hMyLog, (arrObject_3.Extract(0, 16)) As Byte[]

writes the first 16 bytes to file-stream as byte-array
then open the file written with editor shows: 

AABCDEFGHIJKLMNOPAABCDEFGHIJ

the signs written except the ABC...NOP are some kind of delimiter or 
identifiers i guess. 
Where can i find a specification which datatype use which 
delimiters/identifiers ?

wally