Control Data Corporation 3300 Reference Manual page 123

The size of each mass storage block is determined from the BLOCK CONTAINS
clause and/or RECORD CONTAINS clause. If the clause BLOCK CONTAINS
integer-1 TO integer-2 CHARACTERS is given, a block size of integer-2
characters is allocated.
If the clause BLOCK CONTAINS integer-1 TO integer-2 RECORDS and
RECORD CONTAINS integer-3 TO integer-4 CHARACTERS are given, a
block size equal to integer-2 times integer-4 characters is allocated.
In addition to the basic block size, eight characters are added to allow for a
header used internally by the input-output control system. This header is
never accessible to the user program.
Files assigned to TTY or CRT are assumed by MASTER
to
be 1-0 files when
the device is opened.
Examples:
1. OPEN INPUT CARD-FILE.
2. OPEN OUTPUT PRINT-FILEA WITH NO REWIND PRINT-FILEB.
3. OPEN INPUT-OUTPUT MASTER-FILE.
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