What Is a File?A file is a collection of binary symbols stored in

specific locations on a drive and referred to by a unique name.

For example, a file can be a letter created by MS Word, a picture created by Paint, an accounting

report created by Excel, or the sounds of a musical composition. Each of these is represented in a different file format.

What Is a Format?All computer data are in one of two states - binary.

Memory - tiny electric currents, High/Low or On/Off Hard disk - magnetic blips, Present/AbsentCD or DVD – laser burned pits, Present/Absent

We could call these states Jim/John, Apple/Orange, Table/Chair.It works best to call them 0/1.

Suppose you want to represent a letter, a color, a sound in the computer. You need to define a convention for what sequence of 0/1s is the letter G, what is red, how to represent the note of middle C, etc. For example, G is usually 01000111. These conventions are called formats.

How Files Are CreatedEvery file has been created by an application

Hard Disk

Hard Disk or other

Memory

An application In memory The applicationsuch as the program assigns a uniqueWord, Paint, generates the name to what itprogram compiler content of the created and savesetc., is loaded into file to be saved, it on a drive, thememory letter, picture hard disk, flash

program, etc. drive, CD, etc.

Each application uses its own special formats for the kind of files it produces

Formats and File ExtensionsThe file extension tells Windows what the file

format is and which application to use with the file.

Examples:

.DOC, .DOCX - MS Word, Open Office app

.XLS, .XLSX - Excel, Open Office app

.PPT, PPTX - PowerPoint, Open Office app

.JPG - Paint, Internet Explorer

.MP3, .WAV - Windows Media Player

In the Windows Control Panel you can change which applications handle which file extensions.

How Files Are SavedThe application that created the file asks you to:

• Assign a name to the file • Decide where the file should be saved • It may give you a choice of several formats to use

Windows then saves it as you specified.

The application assigns a file extension depending on the format the file is in. The next time you use the file that file extension tells Windows which application should handle it.

How Files Are NamedEvery file has a unique File Name

A file is named when first saved. Windows keeps a record of where files are located in the File Allocation Table. Recorded there is the file’s location, its size in bytes, the date and time when it was created and various file attributes.

File names may contain alphabetic characters, numerals or some special characters such as a hyphen, parenthesis, blank (space), ampersand (&), underscore (_), or tilde(~). You cannot use / \ | ; : < > + = . If you use an illegal character, a pop up will notify you of the error.

Where Files Are LocatedEvery saved file is in some folder on some drive

Information in computer memory is lost when power is turned off. To retain it, data are stored on drives, in folders, as named files.

Drive: A physical device for storing persistent information, either in the computer of attachable to it. In Windows a single capital letter followed by a colon denotes a drive. C: is usually the hard drive.

Folder: An addressing convention used to organize files on a drive. The physical location of a file on a drive is not determined by the folder it is in. Files on a drive not located in other folders are said to be in the Root Directory or Folder. Additional folders are created in the Root to keep related files together and to protect them from being mistaken for other files or accidentally deleted. You can create folders within other folders.

How Files Are RecoveredWindows uses the file’s extension to bring the

matching application and the file into memory. The file can then be processed – viewed, edited, saved

elsewhere, etc. by the application.

Application and file both in

memory

Windows locates application using file extension

Locates file using file name