Software
System System software- program that controls operations of the computer and its devices. Interface between user, application software and computers hardware. two types of system software:
operating System utility programs
OS is intended to be transparent, does not have to be understood. One must know how to use.
System Software
Operating Systems Device Drivers Utilities
DOS Windows Mac OS Linux UNIX
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Operating System
Instructions that coordinate all of the activities among computer hardware resources
coordinates input and output starts up the computer (booting) opening, executing and running applications storing, retrieving files manage files backing up the contents Configure equipment sharing CPU between multiple applications or users
OS - Software Platform
OS is also called software platform. Most applications are software platform dependent. Applications that can run on more than one platform are called cross-platform.
Computers cant function without O.S.
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Operating System
kernel - the core of an OS, contains the most essential and frequently used commands in the OS which are called internal commands. responsible for managing memory, files, devices, clock. When computer is turned on, kernel is moved to memory. Memory resident (internal)- program or instruction that remains in memory while computer is running. Ex. kernel
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Operating System
User interface
kernel
External commands
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Booting
Boot process is a sequence of events that occurs between the time that you turn on a computer and the time that it becomes ready to accept commands. Cold boot - loading an OS into memory after the computer has been powered off completely. Warm boot - process of restarting a computer that already is powered on (CTRL + ALT + DEL). Boot process:
Power up Loading BIOS instructions POST (power-on-self-test) diagnostic test, checks memory, keyboard Loading operating system instructions from the hard disk to RAM Check configuration and customization
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Power-Up checklist
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Boot Disk
Boot disk is a floppy, Zip or CD-ROM disk that contains system files needed to start a computer without accessing a hard disk (use when a hard disk becomes damaged).
Recovery CD supplied by the manufacturer, contains OS files needed to boot the computer plus all of the Windows and applications software files needed to restore your computer to the state it was in when computer was purchased. Windows Startup Disk it loads OS and CDROM drives necessary for your computer to access files on the CD_ROM. Rescue disk - contains OS files plus a special version of the antivirus software that can perform the first wave of virus cleanup in RAM and on the hard disk.
User Interface
User interface determines how the user communicates with the computer. User interface types :
command-line interface (instructions, syntax) GUI (Graphical User Interface) - communication via graphical representation of the computer resources; menu driven.
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Characteristics of OS
Single-user/single tasking task switching Multitasking Multi-user
Single-User
Single-user/single tasking - allows only one user to run one program at a time. It also called serial OS. Early operating systems were single user (MS DOS). Operating system for handheld computers
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Task Switching
Task switching enhances single tasking.
Program that automatically swaps programs in and out of memory to allow smooth transition between them. DOS shell, Windows 3.X - operating environment.
Multitasking
Multitasking allows a single user to run more than one application at the same time. Two or more applications reside in the memory at the same time. Programs run concurrently
Cooperative - CPU access is controlled by the programs being used (Macintosh 7). Preemptive - operating system controls over which program uses the CPU and how long (Win 95 & up). Foreground and background applications
Highly interactive programs like WP gets more CPU time, low priority tasks feeding characters to the printer are given less CPU time.
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Multi-user
multi-user operating system allows two or more users to run a program simultaneously. Networks, minicomputers, mainframes, supercomputers allow hundreds to thousands of users to connect at the same time.
Multiprocessing
multiprocessing supports multiple CPUs running programs at the same time. Works much like parallel processing. Increases computers processing speed. Fault- tolerant computers. Have duplicate CPU, memory, drives. If one component fails, duplicate will operate. (used in banks, airlines reservation).
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Functions of an operating system
managing memory spooling Print Jobs configuring devices memory management - optimize use of RAM
responsible for allocating or assigning data to an memory while they are being processed (time slice). Buffer - an area of memory or storage where data is placed waiting to be transferred to or from an input or output. Virtual memory (VM) - portion of hard disk that works as memory. The area of the hard disk used for VM is called a swap file. Slows down operations. Paging technique- swapping items between memory and storage. Trashing - when system spends much of its time paging.
Virtual disk - part of RAM that assumes job of a disk. Speeds up operations, simulates disk
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Spooling Print Jobs
CPU sends print jobs to the printer faster then printer can print. the print jobs are placed in a buffer (memory or storage area). print job is moved to buffer to free CPU for other tasks. multiple print jobs are placed in a queue (FIFO). print spooler- program that manages print jobs.
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Configuring Devices
Some devices require software called device driver to set up communication between computer and the device.
it accepts instructions from other programs and translates them so the device understands them. every device has its own driver. in windows most device drivers have .drv extension when you boot a computer, the operating system system loads each devices driver.
Plug Play
Plug And and play is the computers ability to recognize new devices and assisting in the installation of the device by loading necessary drivers, and checking for conflicts with other devices.
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File Manager
Organizes files on the secondary storage devices.
Formatting copying moving creating folders
Administering Security
User ID, password file sharing - protecting
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Utility Programs
Utility program performs a specific task
manages computer devices manages programs. most operating systems include several utility programs. There are also a stand alone utility programs.
File viewer File compression Diagnostic utility Disk scanner Disk defragmenter Antivirus Uninstaller Backup utility
Utilities
Purpose
Launch programs Manage files Find files Documentation Customize user interface Configure equipment Disk management
Windows Utility
Desktop, Start Menu Windows Explorer Search or Find Help Control Panel - Display Control panel - Devices Defrag, Scandisk, Format
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File Viewer
File viewer is a utility that allows you to display and copy contents of the file. Windows 98, ME, XP has two viewers in windows explorer.
Quick view - displays contents of text files Imaging Preview - displays graphic file
File Compression
reduces the size of a file. compressed files, zipped .zip (archive files) unzip - uncompress file PKZIP, Power Zip or WinZIP - compresion software
data compression - reduces data storage requirements by substituting codes for repeating patterns of data.
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Diagnostic Utility
compiles technical info about computers hardware and system software. Prepares a report outlining any identified problems. Win98 - DR Watson -diagnoses problem and suggests solution.
Disk Scanner
detects and corrects physical and logical problems on a hard and floppy disk. searches for and removes unwanted files Windows 98, ME, XP has two disk scanner utilities:
Scandisk - detects and corrects problem Disk cleanup - removes unnecessary files.
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Disk Defragmenter
File is fragmented when is stored in noncontiguous clusters Defragmentation reorganizes data stored on a disk, so the files are located in the contiguous clusters.
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Uninstaller
Removes programs, as well as the associated entries in the system files. Registry - in Win95 - stores information necessary to configure the system for users, applications, hardware devices. Replaces Win3.x and DOS .ini file.
Backup Utility
A backup is a copy of files that has been made in case the original files become damaged. Restore - process of restoring data from a backup to the original storage medium. Backup media:
to a tape, floppy disk, zip disk, portable hard drive
Backup procedures:
Full backup Differential backup Incremental backup
backup files may be compressed.
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Antivirus Program
Virus program is a program that copies itself into other programs and spreads through multiple computers.
Types of an operating system
A stand-alone OS - complete operating system that works on a desktop or notebook computer.
DOS Windows 95, 98, Me, XP Windows NT Workstation, Windows 2000 Mac Os OS/2 Warp Unix Linux
network
NetWare Win NT Server, Win 2000 Server OS/2 Server UNIX, Linux Solaris
embedded
Windows CE Pocket PC OS Palm OS
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DOS
Disk Operating System, 16 bit processor developed by Microsoft in the early 1980s command line interface single user later shell added, menu driven
PC-DOS developed for IBM MS-DOS developed for IBM-compatible PCs.
Windows 3.x - multitasking
versions: 3.0,(introduced in 1990); 3.1; 3.11 operating environment for DOS not an oper...