Section+2,+Table+5+-+Hardware+&+OS,+file+systems

Operating Systems Different Types of Operating Systems: Personal Work Group Enterprise Consumers
 * Lower Level: A program that controls the execution of application programs and an interface between applications hardware
 * Primary Controls
 * Control, Error Detection and Response, Accounting
 * 1) Virus Software
 * 2) Screensaver
 * 3) Examples
 * 4) Window 98, Window 2000, Mac OS, Linux
 * 1) Status of accounts
 * 2) Passwords and Activity
 * 3) Resource usage
 * 4) Examples
 * 5) Windows NT Server, Windows XP, Mac OS Server, Linux
 * 1) Archival Operations
 * 2) Job Status
 * 3) Data Mining
 * 4) Examples
 * 5) Windows XP, Windows NT Server, Solaris
 * Ex:
 * 1) Linux
 * 2) Windows XP Embedded
 * 3) Windows CE Net

OS Timeline
 * Frist Generation 1945-1955
 * Vacuum tubes
 * Plug boards
 * Second Generation 1955-1965
 * Transistors
 * Batch Systems
 * Third generation 1965-1980
 * integrated circuits
 * multiprogramming
 * Fourth 1980-2005
 * large scale integration
 * personal computers
 * Next 2005 - ?
 * System connected by high-speed networks
 * wide area resource management
 * cloud computing

File Systems (a data structure on a disk that holds files)


 * Computer hard drive components (SADRAC)
 * spindle
 * arm
 * disk (holds information)
 * read/write head (reads and writes info. on disk)
 * actuator
 * circuit board
 * File systems in different OS have different internal structures

3 ways to allocate space on a hard drive The operating system uses a file system to keep track of the names and locations of files that reside on a storage medium
 * Contiguous- requires each file to occupy a set of contiguous blocks on the disk
 * simple- file designations only need to include starting location and how many blocks are required
 * Dynamic storage allocation is difficult
 * External fragmentation is difficult
 * Files can't grow
 * Linked
 * Solves contiguous allocation problem
 * Each file is a linked list of disk blocks scattered anywhere on the disk
 * no external fragmentation
 * (FAT) file allocation table used to support direct access
 * Indexed
 * Solves external fragmentation and size declaration issues with contiguous allocation
 * Each file contains index block
 * Suffers from wasted space


 * Disk sectors are grouped into clusters
 * FAT(File Allocation Table)- an operating system file that maintains a list of files and their physical location on the disk (of a hard drive)
 * Introduced with MSDOS in 70s
 * Evolved in response to change in names of files and structure, and increasing size of hard drives
 * 3 types of FAT file systems
 * 1. FAT 12
 * 2. FAT 16
 * 3. FAT 32
 * Deleting a file means the OS removes the file name and makes it seem empty, but the information is still there
 * MFT(Master File Table)- an array of records holding attributed for a different file

Fragmentation- as files are added and deleted, files tend to scatter across the disk space This slows performance of reading and writing Defragmentation reorders files

Fragmentation
 * Internal-allocates storage without using it
 * External- free space divided into small pieces over time
 * Data- data broken into memory into many small pieces due to external fragmentation

WinFS
 * allows for a "flattened" non-hierarchical system to search for files based on attributes like the date
 * Can understand arbitrary defined sets of data like "e-mail" "photo" "calendar"

Benefits of winFS:
 * data is easily found
 * information is organized in a way that makes logical sense to people
 * integrated view of information
 * Use of metadata tags and relations

Keywords:

Desktop- A computer designed for desktop use; usually comprises, at a minimum, a central processing unit (CPU), a monitor, and a keyboard as separate units, connected by special cables.

DNS- Refers to a Domain Name Server. A dedicated server or a service within a server that provides DNS name resolution in an IP network. It turns names for Websites and network resources into numeric IP addresses. DNS servers are used in large companies, in all ISPs and within the DNS system in the Internet, a vital service that keeps the Internet working.

File Server- A high-speed computer in a network that stores the programs and data files shared by users. It acts like a remote disk drive. The difference between a file server and an application server is that the file server stores the programs and data, while the application server runs the programs and processes the data.

Server- a server is a computer system that provides services to other computing systems ”called clients” over a network. The term server can refer to hardware (such as a Sun computer system) or software (such as an RDBMS server).

FAT- An area on a hard disk or floppy disk where information is stored about the physical location of each piece of every file on the disk and about the location of unusable areas of the disk. File Allocation Table (FAT) is a partially patented file system developed by Microsoft for MS-DOS and is the primary file system for consumer versions of Microsoft Windows up to and including Windows Me.

NTFS- (NT File System) An optional file system for Windows NT, 2000 and XP operating systems. NTFS is the more advanced file system, compared to FAT32. It improves performance and is required in order to implement numerous security and administrative features in the OS.

Virtual Memory- An imaginary memory area supported by some operating systems (for example, Windows but not DOS) in conjunction with the system hardware. You can think of virtual memory as an alternate set of memory addresses. Programs use these virtual addresses rather than real addresses to store instructions and data.

Hard Drive- The primary computer storage device, which spins, reads and writes one or more fixed disk platters.

CD-ROM/RW Drive- A device that holds and reads CD-ROM discs. CD-ROM drives, which today typically means a CD-RW drive that is a combo CD-ROM, CD-R and CD-RW drive, come in a variety of speeds.

Fragmentation- Refers to the condition of a disk in which files are divided into pieces scattered around the disk. Fragmentation occurs naturally when you use a disk frequently, creating, deleting, and modifying files.

Floppy- Short for floppy disk drive (FDD), a disk drive that can read and write to floppy disks.