Last issue I talked about the general specs of the PERSCI 277 eight inch floppy disk drive. This issue I want to discuss some of the uses for a floppy disc and why anyone would even want one.
But first, let me digress. Since Apple has announced its own Disc II, why should I be telling you about the Persci floppy? Two reasons. 1) Computer Components announced its own floppy as available before Apple did, and 2) I’m using one in another system.
WHY would you want a floppy disc? The two tasks that a floppy performs most often are program storage and data file storage. I feel that data file storage is the most important use you can put your floppy to. Files–data files–can be written in three basic ways. A file is a list of data grouped together for subsequent retrieval. There are three common ways of reading or writing data files. (You might think of this in terms of INPUT or PRINT).
1) SEQUENTIAL – This writes out your data in the same order it was read into the file.
2) RANDOM – This allows you to get your data any way (i. e., in any order) that you choose. Your records are accessed by their relative number on the file.
3) INDEXED SEQUENTIAL – This is by far the most flexible for a programmer, but is the most complex of the three accessing methods and costs (read wastes) a lot of side overhead. For your early needs, skip this one.
All files are composed of records. Records are made up of fields or variables. A typical kind of file is a Name & Address file. In this, the file would be the names and addresses of, say, all the Call-A.P.P.L.E. club members. (Mike, you may have hit upon something! .•• ed.) The record would be all the information about one club member. It might contain seven fields (or variables). For example:
2 ) Street Address
5) Zip Code
6) Telephone number
7) Special interests
The Persci 277 would be able to read 2000 records in five minutes. If you wanted to read and print all the name s of the pe0ple in your name and address file, your printer is liable to be slowing you down, not your floppy disc system.
I’ll be happy to answer any “file” questions at our next club meeting. As soon as I get my APPLE disc up and running, I will write about that. Next issue: File Commands.