Commodore PET User Manual page 251

A good way to visualize what constitutes a file is to picture an address book.
The address book may be a book, file cabinet. or cassette tape. The address book
is then divided into 26 sections by letter: A through Z. Each section contains a
collection of names and addresses of people whose last name starts with the par-
ticular letter. We will cali these alphabetic sections files. Therefore, the address
book is divided into 26 files, each file referenced by a letter:
Berkeley. CA
Steve Alberts
336 Rose 51 654-3211
I--,-Ac.:::0c.:0:...;R..:.;E=-S::.:S:..,Br:-0=-O.:....-K
--r:~~_-
Fil e 1( A )
JoeAdams
A~
533-6564
~~.f4Io---
File 2( B)
~
-File 3(C)
,
G
H
,
,
Gloria Amold
777 Greenfield 456·7890
Hayward. CA
K
,
M
N
o
u
V
W
x:::::-
File 25(Y)
' - - - - - - - - -
~ F
ile 26(Z)
Each file is further divided into records. The na me, address, and telephone
number of each person in the address book constitutes a record:
1",,,,
#2
l,,,,,,
#3
Joe Adams
~
563 Bancroft Way 533-6564
Bend, CA
Steve Alberts
336 Rose St. 654-3211
Berkeley, CA
Gloria Arnold
777 Greenfield 456-7B90
Hayward, CA
} " " , ' #1
file #1
Each record in the address file is divided into four fields. Field #1 contains
the name; field #2 the street address; field #3 the city and state; and field #4 the
telephone number.
Gloria Arnold
777 Greenfield
456-7890
Hayward. CA
--
-
~
field #1 }
field #2
#3
record #3
field
field #4
To get to a field, the file and record numbers must be accessed first. In other
words, to find out in what city Gloria Arnold resides, File #1 and Record #2 must
be referenced first before Field #3 may be accessed. This structuring is
very
im-
portant because it enables large quantities of data to be separated into smaller
units, making it more organized and more easily accessible.
The PET uses two types of files: program files and data files.
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