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Part 3: Your Computer's Filing System

To use your computer effectively, you need to understand a bit about its filing system—namely, how it stores and organizes information on disks. This chapter begins by discussing files, the repositories of programs and data on disks, and other long-term storage media. You will learn about file formats used by various application programs, and about the organization of files into groups known as folders or subdirectories.

The second half of the chapter delves into detail about the disks themselves—the medium on which files are generally stored. By the time you're through, you will know how to choose the right type of disks for your floppy-disk drive(s), protect floppy disks from accidental damage, prepare new floppy disks for use, care for your hard disk, use CD-ROMs and Zip disks, and ward off computer viruses.

What Are Files?

All data on disks is stored in files. A file is a named collection of information stored on a disk. There are two basic types of files: program files, which contain instructions to your computer, and data files, which contain data that you enter through an application program. In Windows, data files are usually referred to as documents, regardless of their actual contents. A spreadsheet or mailing list file is considered to be as much a document as is a word processing file, for example.

Creating Data Files

Unless you delve into programming at some point, most of the files you create will be data files. Every time you enter data in an application program—be it text, numbers, pictures, or anything else—and then save it for the first time, you are creating a new data file. And, because all files, by definition, have names, the first thing the program asks you to do when you issue the command to save is assign a filename. (There are special rules for naming files and folders, which you'll learn more about in the "Rules for File and Folder Names" topic in Chapter 5, "Using Windows.")

Figure 3.1

Unique Filenames

In general, every file on a particular disk must have a unique name. (We'll explain the qualifications to this rule a little later in this chapter, after you learn about folders.) This way, when you tell your computer to find the file LETTER.DOC and copy it into memory, it knows exactly which file you mean. It doesn't need to determine which LETTER.DOC.

Figure 3.2

Use Unique Filenames to Avoid Overwriting Files

You must keep this law of unique filenames in mind when copying files. If you copy a file named LETTER.DOC from disk 1 to disk 2, and disk 2 already has a file named LETTER.DOC, the old version of the letter is completely and permanently replaced by the new one. If you are using Windows, you will be asked to confirm that you want to replace the existing file.

Data Storage Formats

Most application programs have their own unique format for storing data, a format that only makes sense to that one program. For example, the format in which the Lotus 1-2-3 spreadsheet program stores data is not the same as the format used by the Excel spreadsheet. The format that the Microsoft Word word processing program uses is not the same as the format that WordPerfect uses.

File Formats

Special codes that tell the program how to arrange and format the data distinguish the file format used by one program from that used by another. A word processing program arranges data completely differently from a spreadsheet program, for example.

Looking at Files

In general, if you want to see what's inside a particular data file, you need to look at the file from inside the program in which it was created. For example, if you want to see what's inside an Excel spreadsheet file, you need to look at it from within the Excel program. If you try to look at it from within a word processing program or even from within another spreadsheet program, you will probably just see a lot of nonsense characters. Families of related programs (called "suites") such as Microsoft Office can generally read from each other. So, you can view an Excel spreadsheet from within Word.

Figure 3.3

Using Files in Other Formats

Many programs have commands for importing and exporting data in the formats used by other programs. Microsoft Word can import WordPerfect files, for example, translating all the WordPerfect formatting codes to their Word equivalents.

Saving Files in a Generic Format

Occasionally, a program is not capable of opening a file created by another program and interpreting the special codes that file contains. In this case, the file must be saved in a generic format, without any of the special formatting codes specific to one particular program. The most commonly used generic format is one known as ASCII or text-only. (ASCII stands for American Standard Code for Information Interchange and is a set of standardized codes used to represent all the characters you can produce on a typewriter, plus a few others.) After you have saved a file in ASCII or text-only format, you can open it in almost any other program, although you may need to specify the file format when you open the file or issue a special import command. Consult your program documentation for information on saving and using ASCII or text-only files.

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