Download Pathway Introduction: Information Technology

Operating Systems
Who’s in charge in there?
Types of Software
• Application Software :
Does things we want to do
• System Software :
Does things we need done
Low level details
Operating System
• Operating System :
Software that manages the operation of a
computer
• Not all computational systems have an OS
– Early computers
– Embedded systems
Operating Systems
• PC Operating Systems
– Windows
– *nix
• Linux
• MacOS X
• Phone OSes
– iOS
– Android
– Windows
Operating Systems
• What is Linux?
https://www.youtube.com/watch?v=5ocq6_3-nEw
Varieties of OSes
• Embeded
Varieties of OSes
• Batch
– Submit list of jobs
Varieties of OSes
• Real Time / Dedicated
What do the do?
• API : Application Programming Interface
• Set of functions software can do
• OS provides API to other programs for
– Reading files
– Using a network
– Drawing windows
– Getting mouse position
What do they do?
• Manage hardware
resources
– Provide an abstraction for
resources
– Allocate scare resources
Resource Scarcity
• Resources scarce in
– Time
• Processor
• IO / Disk
– Space
• Memory
• Disk
• OS responsible for allocating scarce resources
Resources - Processes
• OS manages what process(es) are running
– Programs take turns on processor
• Run until time limit or need to wait
• OS handles all hardware events
http://computerscience.chemeketa.edu/cs160Reader/OperatingSystems/ProcessManagement.html
Resources - Memory
• Main Memory :
– Where running programs & data are stored
– Computer may have ~4 or 8 billion bytes
– Programs can "use" up to 200 trillion bytes
(48 bit addresses)
Virtual Address Space
• Program uses virtual addresses
– Nice, orderly
• OS maps to
– Main memory
– Hard drive (Virtual Memory)
Other Resources
• Hard Disk
– Abstraction:
• Programs ask for files
("MyEssay.doc"), OS deals with
details
– Allocation:
• What users/programs get to work
with which files
Other Resources
• Monitor:
– Abstraction
• How exactly to draw to screen
– Allocation:
• What program's get to draw in what order
Other Resources
• Monitor:
– Abstraction
• How exactly to draw to screen
– Allocation:
• What program's get to draw in what order