Control Data Corporation 3300 Reference Manual page 280

Reference Code
F-2
Resultant Block Format
Unblocked, fixed-length logical records. Size of physical record is computed
from record description.
Unblocked logical records. Physical record may be variable on magnetic
tape, but on mass storage the record is always fixed length with size equal to
integer-4.
illegal combination. Universal records must always be blocked.
Blocked or unblocked logical records, depending on whether integer-l is a
multiple of the record description length. Size of physical record is always
integer-l characters.
Blocked logical records. Size of block is always integer-l characters on mass
storage; the block may be variable on magnetic tape.
Blocked, fixed-length logical records. Size of block is equal to integer-l
times the length of the record description.
Blocked logical records. Size of block is equal to integer-l times integer-4
for mass storage; block may be variable on magnetic tape.
Blocked logical records. Block size is always integer-2 characters on mass
storage; may be variable length on tape.
Blocked logical records. Mass storage block size is equal to integer-2 times
the length of the record description; may be variable on magnetic tape.
Blocked logical records. Mass storage block size is equal to integer-2 times
integer-4; may be variable on tape.
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