IBM 1130 User Manual page 87

Frequency of Changes to Your File
A third consideration in deciding on card or disk is
the number of times the data in your file must be
changed, and the difficulty involved in changing it.
Some amount of change is inevitable; in a payroll
file every week will bring raises, new dependents,
changes of address, etc. These minor changes do
not present much of a problem.
With a card file it is very easy; a new card is
punched and substituted for the old card.
With a disk file it is somewhat more involved;
you must run a change program, which reads the
new data from cards or the console keyboard and
inserts it in the proper place on the disk record.
Major changes are another matter - new em-
ployees, a new group of items in stock, etc. Here
again, changing a card file is relatively easy, and
changing a disk file more difficult. It is a simple
matter to punch a master card for new item number
1 705 and place it in the card deck between items
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1704 and 1800. It is not quite so simple on the disk,
where items 1704 and 1800 are probably adjacent,
with no space between them. Either item 1 705 is
placed in a special area, with a special routine to
find it, or the entire file is reorganized, moving
every item after 1704 "down" one position to make
room for item 1705. This also would require a
special program or routine.
If a data file is subject to frequent major (organ-
izational) changes, you may add a few points to the
"card file" side of the balance. These points may
or may not be enough to swing the decision, since
the first two items (processing order and number
of files) are more important, and generally favor
disk use.
Remember, when you change a field on a card,
you still have the old card; when you change some
data on the disk (usually an entire record at a time!),
the old information is gone. Therefore, special
care must be taken to ensure that disk changes are
processed correctly the first time.