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METHOD:
(cont .)
62
unconditional read operation of the current sector into the specified file's I/O
buffer.
No information is transferred to the user.
Close
Calling sequence:
BRM
02
*QSYS
FDT
Close the file whose number is specified in the fourth word of the file descrip-
ti on tabl e.
Words two and three are ignored.
II
CI ose" corresponds to an un-
conditional write operation upon the current sector from the specified file's
I/O buffer.
Since a "write" call does not always result in an I/O operation,
"close" is used to ensure that the file's output buffer is "dumped" onto the RAD.
Read
Call ing sequence:
BRM
03
*QSYS
FDT
Read from the file whose number is specified in the fourth word of the file de-
scription table.
Word three specifies the number of words to be read, and word
two specifies the area into which the information is to be transferred.
The speci-
fied file must be open; i.e., an "open" operation must precede the first "read"
operation.
Variable length records may be read under "count control
II
by specifying their
length to be unknown ((word three) <0).
The file management routine will then
assume the record length to be specified in bits
3-8
of the first word in the record.
Write
Calling sequence:
BRM
04
*QSYS
FDT
Write onto the file whose number is specified in the fourth word of the file de-
scription table.
Word three specifies the number of words to be written, and
word two specifies the area from which the information is to be transferred.
The specified file must be open;
i.
e.,
an "open" operation must precede the
fi
rst "wri te
II
op~rati
on.
Before returning to the calling program, the file management routine clears the
contents of the next word in the output buffer; however, the next write will
"overwrite" the "clear".
That is, it is as though every write were followed by
a write end-of-file and a backspace.
This feature is used by the processors and
loader to identify the end of the
Xl, X2,
and BO files, whose records could
not otherwise contain zero in the first word.
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