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System Software

Chapter 4 of Computers: Understanding Technology (Third

edition)

1September 16, 2009 - William Pegram

System Software in Context

• Hardware– Input (Ch. 2)– Processing (Ch. 2)– Output (Ch. 3)– Storage (Ch. 3)

• Software– System software(Ch. 4)– Application software (Ch. 5)


System Software

• Operating Systems

• Utility Programs

• Language Translators – Compiler, Interpreter


Operating Systems

• When computer is started, part of operating system is loaded into random access memory (RAM) from the boot drive (typically the hard drive)

• Functions of operating system– Managing main memory– Controlling peripheral devices– Managing file operations– Monitoring system performance– Providing user interface


Operating System Functions

• Output buffers – selected areas of RAM which hold data waiting to be transferred to an output device – This frees the CPU to move on to something else; output device will often be slower – print spooling is example

• Multitasking – User can work on more than 1 application at the same time

• Drivers – programs that allow the operating system to communicate with a peripheral device – the driver is often specific to a specific device, manufacturer and model number; typically this means that the application program need only know how to communicate with Windows and not with each peripheral device


Operating System Functions (cont.)

• Security features– Operating system can force user to enter a

correct username and password to access the computer

– Windows XP and Windows Vista can provide multiple user accounts on a single machine and different levels of privileges among the accounts


User Interfaces

• Command line – e.g. DOS

• Graphical User Interface (GUI) – e.g. Windows

• Graphical user interface was used in the Alto computer developed by Xerox Palo Alto Research Center, and later used in the Apple Lisa and Macintosh computers


Elements of GUI

• On-Screen desktop with graphical elements displayed – icons, buttons, etc.

• Display windows – title bar, scroll bar, and other common features

• Menus with drop down menus• Toolbars with icons• Dialog boxes to provide information and prompt

responses – tabs, radio buttons, checkboxes, text boxes, OK/cancel buttons


Personal Computer Operating Systems

• Windows XP (ITN 114)

• Windows Vista

• Macintosh

• IBM OS/2

• Linux (ITN 170, ITN 270)


Server Operating Systems

• Some operating systems are used with networks, allowing multiple users to connect to the server


Server Operating Systems

• Novell NetWare• Windows NT Server• Windows 2000 Server (ITN 111)• Windows 2003 Server (ITN 115)• Windows 2008 Server • Unix (ITN 171 and ITN 271)• Linux (ITN 170 and ITN 270)


Wireless Device Operating Systems

• Palm OS

• Windows Mobile


Utility Programs

• Antivirus – Norton, Symantec, McAfee• Firewalls – security system that acts as

boundary to protect computer or network• Diagnostic• Uninstaller – remove all files associated with a

program• Disk scanner – identify bad sectors• Disk defragmenters • File compression – WinZip, PKZIP, and Stuffit


Utility programs (cont.)

• Backup

• Disk toolkits – fix problems with a disk

• Spam blocker

• Anti-spyware – Windows Defender


Language Translators

• Programmers generally write programs in high-level languages – Java, COBOL, Fortran

• Compilers translates entire program into machine language file; that file is then executed whenever program is run

• Interpreter translates one statement at a time without producing a file, so repeated runs require interpreter each time
