31-05-2013, 12:29 PM
Operating Systems: Basic Concepts and History
Operating Systems.pdf (Size: 243.14 KB / Downloads: 330)
What is an Operating System?
Any code that runs with the hardware kernel bit set
An abstract virtual machine
A set of abstractions that simplify application design
Files instead of “bytes on a disk”
Core OS services, written by “pros”
Processes, process scheduling
Address spaces
Device control
~30% of Linux source code. Basis of stability and security
Device drivers written by “whoever”
vendor’s
Software run in kernel to manages a particular vendor s
hardware
E.g. Homer Simpson doll with USB
~70% of Linux source code
OS is extensible
Drivers are the biggest source of OS instability
Why do we need operating systems?
Convenience
Provide a high-level abstraction of physical resources.
Make hardware usable by getting rid of warts & specifics.
Enable the construction of more complex software systems
Enable portable code.
MS-DOS version 1 boots on the latest 3+ GHz Pentium.
Would games that ran on MS-DOSv1 work well today?
Efficiency
Share limited or expen
History of Operating Systems: Phases
Phase 1: Hardware is expensive, humans are cheap
User at console: single-user systems
Batching systems
Multi-programming systems
Phase 2: Hardware is cheap, humans are expensive
Time sharing: Users use cheap terminals and share servers
Phase 3: Hardware is very cheap, humans are very expensive
Personal computing: One system per user
Distributed computing: lots 12
of systems per user
Phase 4: Ubiquitous computing/Cloud computing
Cell phone, mp3 player, DVD player, TIVO, PDA, iPhone, eReader
Software as a service, Amazon’s elastic compute cloud
What is cloud computing?
Cloud computing is where dynamically scalable and
often virtualized resources are provided as a service
over the Internet (thanks, wikipedia!)
Infrastructure as a service (IaaS)
Amazon’s EC2 (elastic compute cloud)
Platform as a service (PaaS)
Google gears
Microsoft azure
Software as a service (SaaS)
gmail