1.3 Operating systems  (Page 2/9)

Commonly, the extension indicates the content type of the file, for example,

exe: executable file, txt : text file, pas : pascal source file, cpp : C++ source file. . .

In MS-DOS, Microsoft Windows, you can use wildcards ? and *. ? marks a single character while * Marks any sequence of characters.

Example *.pas : all pascal source files of the current directory , possibly t1.pas, book.pas. . .

b*.cpp : all C++ source files beginning with b.

File management

Structures of Disks

Floppy disk can be single-sided or double-sided. Data is stored on a disk in circular tracks. Tracks are numbered 0, 1. . . Each track is broken up into arcs called sectors. Each sector stores a fixed amount of data. The typical formatting of these media provide space for 512 bytes (for magnetic disks) or 2048 bytes (for optical discs) of user-accessible data per sector.

Formatting (initializing) a disk

Disk formatting is the process of preparing a hard disk or other storage medium for use, including setting up an empty file system. Formatting a disk includes the following tasks:

• Determines the sector size and placement.
• Slices the disk into sectors by writing codes on the disk.
• Locates bad spots on the disk, locks it out to prevent the bad spot from being used.
• Side number, track number, sector number Þ address : locates where on the disk the computer will store the data.

Computer file system

In computing, a file system is a method for storing and organizing computer files and the data they contain to make it easy to find and access them. File systems may use a data storage device such as a hard disk or CD-ROM and involve maintaining the physical location of the files, or they may be virtual and exist only as an access method for virtual data.

More formally, a file system is a set of abstract data types that are implemented for the storage, hierarchical organization, manipulation, navigation, access, and retrieval of data.

A typical file system may contain thousands (or even hundreds of thousands) of directories. Directory (catalog, or folder) is an entity in a file system which contains a group of files and/or other directories.Files are kept organized by storing related files in the same directory. A directory contained inside another directory is called a subdirectory of that directory. Together, the directories form a hierarchy, or tree structure.

The first or top-most directory in a hierarchy is the root directory (symbolized by the back slash \)

The current directory is the directory in which a user is working at a given time.

Full name of a file

A full filename includes one or more of these components

• Drive (e.g., C:)
• Directory (or path) file
• Base name of the file
• Extension

An operating system includes several files, for instant, MS-DOS includes MSDOS.SYS, IO.SYS, COMMAND.COM . . .

Some common operating systems

Ms-dos

MS-DOS (short for Microsoft Disk Operating System) is an operating system commercialized by Microsoft. It was the most commonly used member of the DOS family of operating systems and was the dominant operating system for the PC compatible platform during the 1980s. It has gradually been replaced on consumer desktop computers by various generations of the Windows operating system.