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SYSTEM DESCRIPTION
24.2 -- File
St~ucture
F E D
C
B
A
9 8 7
6 5 4
3
2
1
0
00
sow
0
02
SDW 1
04
Other SDWs
TERMINATOR
Zeroes
74
: BYTES IN LAST SECTOR :
76
NUMBER OF SECTORS TO LOAD
78
STARTING LOAD ADDRESS
STARTING E'XECUTION ADDRESS
7C
ZERO
7E
ZERO
24.2.2 File rormats
MDOS
deals with
~our
types of rile formats on diskette:
user-define<L memor'l--imagel
binary record, and
ASCII
record.
User-defined riles
are
dealt with by MDOS at the
sector
level.
MDOS
will
keep track of where the rile is and will
onl~
allow access to the rile by logical sector number.
The
user has the responsibility
or
formatting the
data
within the
sectors in the manner suited to his application.
Memory-image
~iles
include all files whose contents
are
to
be
loaded
into memory directly rrom the diskette by the
MDOS loader.
Memory-image
riles
are
allocated
contiguous
space
on
the diskette.
The only information retained about
where the content is to be loaded is kept in the file's
RIB.
The
data
within
the sectors
or
the rile contain no load or
record information.
.It is merely an
image
Or
a
block
of
memory
to be loaded into.
Due to the nature of the diskette
controller, MDOS programs can only be loaded in multiples
of
eight
bytes,
A
Turther restTiction placed on memory-image
Page
24-10
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