Partitioned Direct; Summary - IBM 1130 User Manual

Section
Subsections
Page
85
10
I
30 02
Partitioned Direct
The disk addressing used by 1130 FORTRAN makes
this method applicable in some cases. At one in-
stallation, there are about 150 employees, each
with a four-digit employee number. The first two
digits indicate the department number; the second
two digits are sequential numbers. The distribution
is as follows:
Number of
Maximum Range of Possible
Dept. No. of
Employee Employee
No. Employees
Numbers
Numbers
1
5 101 - 110 10
3
35 301 .. 340 40
4
10 401 - 420 20
5 10 501 - 520 20
6
30
601 - 650 50
7 60
701 - 770 70
10 10
1001 - 1020 20
11
20 1101 - 1130 30
12 20 1201 - 1230
30
15
50 1501 - 1570
-1.Q.
250 360
This user noticed that he could use this break-
down of employee numbers to advantage by setting
up ten files:
DEFINE FILE
DEFINE FILE
DEFINE FILE
DEFINE FILE
DEFINE FILE
DEFINE FILE
DEFINE FILE
DEFINE FILE
DEFINE FILE
DEFINE FILE
1 (10,X,U,Nl)
3 (40, X, U, N3)
4 (20,X, U, N4)
5 (20,X,U,N5)
6 (60,X, U, N6)
7 (70,X, U, N7)
10 (20, X, U, NlO)
11 (30,X, U, NIl)
12 (30, X, U, N12)
15 (70,X, U, N15)
requiring a total of 360 records to hold 250 em-
ployees. This wastes about one-third of the available
records but results in much simplified programming,
since the user can read the employee department
and man number from a card:
77 FORMAT (I2, 12)
:READ (2,77) NDEP, NEM
and access that employee with a
READ (NDEP'NEM) data
statement.
Many numbering systems fit this general type and
may lend themselves to this disk organization approach.
Summary
Each of the techniques described above has its advan-
tages and disadvantages, as has been pointed out
earlier. Ingeneral, indexed sequential files require
more core and disk storage (because of the index)
and tend to increase processing time because of the
searching invoived. Random (direct) organizations
make for fast access, with little extra core or disk
requirements, but are usually difficult to set up
because of the synonym problem.