Pag. 104 di 152
Structure of an Homogeneous File containing no external single allocation variables.
Record
Number
Record
Size
(bytes)
Field name and size
Type
Value
Header size
(
1 byte
)
unsigned
integer
h
Data record size
(
1 byte
)
unsigned
integer
d
Reserved
(
1 byte
)
unsigned
integer
0
Reserved
(
1 byte
)
unsigned
integer
0
Reserved
(
1 byte
)
unsigned
integer
0
Reserved
(
1 byte
)
unsigned
integer
0
DIRECTORY flag
(
1 bit
)
Flag
0
OUTPUT flag
(
1 bit
)
Flag -
NON HOMOGENEOUS flag
(
1 bit
)
Flag
0
Header definition structure
(
4
bytes)
RAW flag
(
1 bit
)
Flag
0
Reserved
(
1
byte)
unsigned
integer
0
Descriptor list size
(
1
byte)
unsigned
integer
s
Descriptor Vi
1
Descriptor Vi
2
...
Descriptor Vi
p
- -
Descriptor Vem
1
-
-
Descriptor Vem
2
-
-
... -
-
Variable
definition
structure
(
s+2
bytes)
Descriptor list
(
s
bytes)
Descriptor Vem
q
-
-
0
h
(
h
≤
238)
Possible unused space
-
-
Vem
1
-
-
Vem
2
-
-
: :
:
1
d
(
d
≤
238)
Vem
q
-
-
Vem
1
-
-
Vem
2
-
-
... :
:
2 d
Vem
q
-
-
: :
: :
:
Vem
1
-
-
Vem
2
-
-
... ...
...
N
(
N
≤
9999)
d
Vem
q
-
-
Vi = Internal allocation variable
Vem = External multiple allocation variable
If the data definition structure contains at least one external allocation descriptor, the data section of the
file is organized as follows:
−
the file has as many data records as single external allocation descriptors;
−
the
n
th
data record contains:
the variable defined from the n
th
single external allocation descriptor;
all the variables defined by external multiple allocation descriptors, in the order listed
in the variable definition structure.
