System Software Chapter 4 of Computers: Understanding Technology (Third edition) 1September 16, 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) 2September 16, William Pegram

System Software Operating Systems Utility Programs Language Translators – Compiler, Interpreter 3September 16, William Pegram

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 4September 16, William Pegram

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 5September 16, William Pegram

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 6September 16, William Pegram

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 7September 16, William Pegram

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 8September 16, William Pegram

Personal Computer Operating Systems Windows XP (ITN 114) Windows Vista Macintosh IBM OS/2 Linux (ITN 170, ITN 270) 9September 16, William Pegram

Server Operating Systems Some operating systems are used with networks, allowing multiple users to connect to the server 10September 16, William Pegram

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) 11September 16, William Pegram

Wireless Device Operating Systems Palm OS Windows Mobile 12September 16, William Pegram

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 13September 16, William Pegram

Utility programs (cont.) Backup Disk toolkits – fix problems with a disk Spam blocker Anti-spyware – Windows Defender 14September 16, William Pegram

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 15September 16, William Pegram