Control Data Corporation 3300 Reference Manual page 46

3.5.2
BLOCK CONTAINS
3-12
This clause specifies the size of a block or physical record.
BLOCK CONTAINS [integer-1 TO] integer-2
l
CHARACTERSI
RECORDS
BLOCK CONTAINS is required in a file description entry unless the block
contains exactly one logical record. A file assigned to TTY or CRT cannot
be blocked.
Integer-1 and integer-2 are positive integers.
For a mass storage file the size is stated in terms of RECORDS. The
CHARACTERS option should be used if one of the following situations exists:
• Logical records extend across blocks
• The block contains padding, an area not contained in a logical record
• Logical records are grouped in such a manner that an inaccurate
block size is implied
When the CHARACTERS option is used, the physical record size is specified
in terms of the number of characters in the physical record. Characters are
specified in standard data format regardless of their types.
If only integer-2 is shown, it represents the exact size of the physical record.
If integer-1 and integer-2 are both shown, they refer to the minimum and
maximum size of the physical record respectively.
If logical records of differing size are grouped into one physical record, the
end of the logical record must be explicitly defined in the record description
entry unless the RECORD CONTAINS DEPENDING ON option is used. The
maximum file block size is 131,067 characters. Appendix F describes
COBOL/MASTER file blocking formats.
Block
A block is a physical unit of data that is convenient for storage on an input or
output device for a particular computer. It is identical with physical record.
The block size has no direct relationship to the size of the file containing it,
or to the size of logical records contained in the block.
A
block is normally
composed of one or more logical records, or a portion of a logical record.
Logical Record
A COBOL logical record is a group of related information, uniquely identifiable,
and treated as a unit. The concept of logical record is not restricted to file
data but is carried over into the definition of working storage items. Logical
records, whether in the File Section, Working Storage, or Common Storage
Sections are defined by record description entries (section 3.2.3).
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