Operating System Basics - Computing Fundamentals - page 93

Table.4 2 Common File Extensions
Extension File Type Associated Application

txt Text Notepad, WordPad, Microsoft Word

gif, png, jpg, tif Photo or graphic Paint, Photoshop, or almost any other

photo editing program

doc, docx, docm Word processing document Microsoft Word, some other word process-

ing programs also support

rtf Word processing document WordPad, Microsoft Word, or almost any

word processing program

xls, xlsx, slxm Spreadsheet Microsoft Excel

ppt, pptx, pptm Presentation Microsoft PowerPoint

mdb, accdb Database Microsoft Access

pdf Portable document format (platform-independent

formatted document)

Adobe Reader, Adobe Acrobat, limited sup-
port in Microsoft Word

xps XML document format (Microsoft-specific

platform-independent formatted document)

XPS Viewer, Windows 7, Windows 8, lim-
ited support in Microsoft Word

exe, com, bat Executable program files n/a

dll, ini, dat Helper files for programs and for Windows itself n/a

zip Compressed archive file Windows Explorer, or a third-party program

such as WinZip

Table 4.2 shows some common default application assignments, but
the actual application assigned to a particular extension depends on the
settings in your operating system. You can configure the OS to associate
a file type with any of the applications you have installed on your com-
puter. When an extension is assigned to an application, and you double-
click a data file with that extension, the data file automatically opens in
the associated application (provided, of course, that the application is
capable of handling that file type).

Backups
Because storage media sometimes fail, it's important to back up impor-
tant files frequently. Businesses spend thousands of dollars on robust,
automated systems that back up their servers nightly, as well as key files
on individual computers in some cases. Home and small-business users
can use smaller backup systems designed for individual PCs.

Backup software can save your backup files to external media, such as
a writeable DVD or an external hard drive, or to a network or Internet
location. To save space on the backup media, backup software cre-
ates its own compressed archive files in its own proprietary format. To
restore from the backup, you must use the same backup software that
was employed to create the backup. A backup can span multiple discs or
volumes, and can include multiple archive files. The collection of archive
files created for a single backup instance is called a backup set .

backup software Software that enables and
automates the process of backing up files to
external media.

backup set A set of backup files created during
a single backup operation.

Each time backup software runs, only a small portion of the files will
have changed since the last backup was created. In order to reduce the
amount of time the backup takes, not all storage is fully backed up every
time. Instead, the backup software reads each file's archive attribute
(sometimes called an archive flag). When a file is backed up, its archive
attribute is turned off. When the file changes, its archive attribute turns

archive attribute A file attribute that indicates
whether or not a file has changed since its last
backup.