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CMPE003 – Personal Computer Concepts. Hardware and Software Winter 2004 Instructor: Scott Cooper scooper@soe.ucsc.edu. Lab sections. Monday 1-3pm Tuesday 10am-12pm Thursday 2-4pm All sections in Oakes 205. Chapter 3: Operating Systems. Software in the Background. The bad old days.
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CMPE003 – Personal Computer Concepts Hardware and Software Winter 2004 Instructor: Scott Cooper scooper@soe.ucsc.edu
Lab sections • Monday 1-3pm • Tuesday 10am-12pm • Thursday 2-4pm All sections in Oakes 205
Chapter 3: Operating Systems Software in the Background
The bad old days • Command line (text) input: wp /p epson c:\templates\equipment.doc • Invokes the program wp on the named file with an option switch (/p) and parameter (epson)
The Mac is born “Obviously it was true that … it would be a good thing to make computers more accessible to a less technical audience – if not for altruistic reasons, then because those sorts of people constituted an incomparably vaster market.” Neal Stephenson, In the Beginning… There Was The Command Line
Layers GUI Command Interpreter Operating System
GUIs • Graphical User Interface created at XEROX PARC • Sometimes called WIMP (Windows, Icons, Mouse, and Pointing) • Unleashed on the world by Apple in 1984 • Two steps back: Windows 3.x released in 1990
Shared resources • Memory • CPU • Storage • Printer • Network • Other devices and peripherals
OS initiates transfer of program code Word.exe Starting applications • What happens when you start a program? Storage Memory Input Processing Output OS
Memory allocation • OS wouldn’t leave a hole, but… unused Operating System Word.exe Solitaire IE • Storage (memory, disk) becomes fragmented over time
Virtual memory • What if it doesn’t all fit? • Treat disk like an extension of memory and move stuff back and forth as needed • Slows processing down • Excessive transfer between memory and the disk is called thrashing You can never be too rich or too thin, or have too much RAM.
File types • How does the OS know which application to open your file with? • Windows uses a 3-letter extension
One thing at a time • CPU can’t do two things at once • Multiprogramming or multitasking makes it look like it by switching rapidly • Who runs next? • For how long? The OS schedules the CPU amongst running programs.
File systems • OS maintains a hierarchy of directories on each disk • Can contain files as well as other directories • Shown as folders in the GUI c:\documents\nicole party music pictures rock dance Invite.doc shins
Device drivers • Programs cannot support every manufacturer’s hardware • Driver models abstract different types of hardware • Manufacturers provide the driver code to implement the model • Programs can treat all models of printers, or removable storage, etc. as if they worked exactly the same
The short version • An operating system allows programs to act as though they have exclusive access to machine resources, while actually sharing them among many programs