| You can download any type of computer file, but not every file or program you find online works on every type of computer. "Duh!" you might think. But you'd be surprised how often people forget this. Web browsing enables different kinds of computers to all look at the same online content, so after a while people tend to forget that on the Web, PCs, Macs, and other types of computers each use different kinds of files and programs. When you search for files and programs, you must make sure that the ones you choose are compatible with your computer type, and often also with your operating system (Windows 95/98/Me/NT/2000/XP; DOS; Mac OS9 or OS X; UNIX flavor; and so on). The Two File Types: Program and Data Although there are dozens of different types of files, they all generally fall into either of two groups: -
Program files ” A program file contains a program ”a game, a word processor, a plug-in, a utility, and so on. Program files are almost always designed to run on only one type of computer and operating system. For example, a program file designed for a Mac typically will not run in Windows. However, many programs are available in similar but separate versions, one for each system type. -
Data files ” A data file contains information that can be displayed, or used in some other way, by a program. For example, a word processing document is a data file, to be displayed by a word processing program. Like program files, some data files can be used only by a particular program running on a particular computer type. But most data file types can be used on a variety of systems.  Popular files are usually available from multiple servers, spread across the continent or globe. Often, a downloading page will refer to the servers as mirror sites because they all offer an identical copy of the file, a "mirror image." | Common Data File Types on the Net When you encounter a link to a file, you'll usually have no trouble telling what system the file is made for. Often, before arriving at the link, you will have navigated through a series of links or form selections in which you specified your system type, so when you finally see links to files, they all point to files that can run on your system. In other cases, the link itself ”or text near the link ”will tell you the system requirements for the file. System requirements are the computer type, operating system, and (for a data file) program required to use a particular file. Some files you'll encounter have special hardware requirements as well, such as a particular amount of memory. Even when the link doesn't fill you in, you can often tell a file's system requirements by its filename extension, the final part of the filename that follows the period. (For example, in the filename MONTY.DOC , the extension is DOC .) Table 14.1 shows many of the most common file types online.  Data files can often be converted and used by programs other than those in which they were created. For example, nearly all full-featured word processing programs can convert Microsoft Word ( .doc ) files so you can read or edit them. Most spreadsheet programs can handle an Excel or Lotus 1-2-3 file. If you lack the required program for using a particular kind of data file, check out any similar program you already own to see whether it can convert a file of that type. | Table 14.1. Common File Types You'll Find Online for Downloading | Extension | Type of File | Requirements | | .exe , .com | Program file (a game, utility, application, and so on) | Runs on one (and only one) type of system. Always read any text near the link to be sure that a particular .exe or .com file will run on your computer. | | .doc | Word document | Can be opened and edited in either the Windows or Mac version of Word, or Windows' WordPad program. | | .pdf | Adobe Acrobat document | Can be opened in the Adobe Acrobat Reader program (available for a variety of systems) or in a browser equipped with an Adobe Acrobat plug-in. Can also be converted and displayed by some word processing programs. | | .xls | Excel spreadsheet | Can be opened and edited in either the Windows or Mac version of Excel. | | .txt , .asc | Plain text file | Can be opened in any word processor or text editor (such as Windows Notepad) on any system, and displayed by any browser. | | .wri | Windows Write document | Can be displayed by Windows Write (in Windows 3.1) or WordPad (in Windows 95/98/NT/XP). | | .avi , .mp3 , .mov , .qt , .mpg , .au, .mid , .snd | Various types of media files | Can be run by various player programs, or by your browser if it is equipped for them. | | .zip | Archive, containing one or more compressed files | Must be decompressed ( unzipped ) before the files it contains can be used; see "Working with Zip Files" later in this chapter. | | Very few program files are designed to run on both Macs and PCs. However, if you use a PC, you should know that some programs work in multiple PC operating systems. For example, there are programs written to run in both Windows 3.1 and Windows 95/98/Me, and sometimes DOS, as well. By and large, programs written just for DOS or Windows 3.1 will also run in Windows 95 or NT, although the reverse is never true. And most Windows 95 programs will run in Windows 98/Me or NT (or later versions of Windows), but some NT programs will not run in Windows 95. A very few specialized utility programs written for Windows 98/Me/2000/XP will not run in Windows 95. If you use a PowerPC-based Mac, you know that you can run some Windows programs on your Mac using a Windows "emulator." You probably also know that those programs do not run as well there as native Mac programs do. A program always runs best on the system for which it was written, so favor choices that match what you have. And even if you have a PowerPC-based Mac, always favor true Mac files over PC versions. | |
