Commodore 1581 - Chapter 4: Sequential Data Files

PART TWO
ADVANCED OPERATION AND PROGRAMMING
CHAPTER 4
SEQUENTIAL DATA FILES
A file on a diskette is just like a file cabinet in your office^—an
organized place to put things. Nearly everything you put on a diskette
goes in one kind of file or another. So far all you've used are program
files, but there are others. In this chapter you'll learn about sequential
data files.
The primary purpose of a data file is to store the contents of
program variables, so they won't be lost when the program ends. A
sequential data file is one in which the contents of the variables are
stored "in sequence," one right after another. You may already be
familiar with sequential files from using a DATASSETTE™, because
sequential files on diskette are just like the data files used on cassettes.
Whether on cassette or diskette, sequential files must be read from
beginning to end.
When sequential files are created, information (data) is trans
ferred byte-by-byte, through a buffer, onto the magnetic media. Once
in the disk drive, program files, sequential data files, and user files all
work sequentially. Even the directory acts like a sequential file.
To use sequential files properly, we will learn some more BASIC
words in the next few pages. Then we'll put them together in a simple
but useful program.
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