Download introduction to operating system

CmpE 241
Fall 2006
CHAPTER 1- INTRODUCTION TO OPERATING SYSTEM
Read: Tanenbaum Ch. 1.
Computer System Overview
A computer system consists of hardware and software that
are combined to provide a tool to solve specific problems.
Hardware Resources
Processor (CPU):
instructions.
The brain of the computer. Executes
Memory:
Stores program and data.
A typical memory hierarchy: Registers, Cache, Main
Memory(RAM), Magnetic disk, Magnetic Tape.
Input / Output (I/O) controllers:
I/O devices.
Disk device:
Transfers data to and from
Long term storage for data.
Software Classification
System Programs: Provides a general environment in which
programmers can create specific applications.
Operating System, Application Software’s(compilers, editors,
command interpreter, etc.)
Application Programs: Intended to solve a specific problem.
Word processing, spread sheets, database systems.
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Banking
System
Airline
reservation
Web
browser
Command
Compilers
Editors
interpreter
Operating system
Application programs
System
Programs
Machine language
Hardware
Microarchitecture
Physical devices
A Computer system consist of hardware, system programs, and
application programs
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What is an Operating System?
 A program that acts as an intermediary between a user of
a computer and the computer hardware
 OS goals:
o Control and execute user programs
o Make solving user problems easier
o Make the computer system convenient to use.
 Ultimate goal is to use the computing resources in an
efficient and effective manner.
 The OS is the part of the system programs that manages
the utilization of the hardware used by other system
programs and all application programs.
 It is the system program that acts between the hardware
and the user programs.
 Operating System provides services to user programs.
o Through system calls / message passing
o File system service
o I/O service
o Memory service
 OS hides hardware from user programs.
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Computer System Components
Hardware: Provides basic computing resources (CPU, memory,
I/O devices, network connections)
Operating System: Controls and coordinates the use of the
hardware among the various applications programs for various
users.
Application programs: Define the ways in which the system
resources are used to solve the computing problems of the
users (compilers, database systems, video games, business
programs).
Users: Require management and provisioning for (people,
machines, other computers).
Abstract View of System Components
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Operating System Definitions
Resource allocator: Manages and allocates resources between
the processes and the users(CPU, memory, file storage, I/O
devices, etc.).
Control program: Controls the execution of user programs and
operations of I/O devices.
Kernel: The one program running at all times in the memory
(all else being application programs). It forms the core of the
operating system.
Shell(command interpreter): It is the interface between the OS
and the user. It allows the user to instruct the machine and to
run programs.
History of Operating Systems
First Generation:
*1945-1955
*Vacuum Tubes
*OS: Plugboards
Second Generation:
*1955-1965
*Transistors
*OS: Batch Systems
Third Generation:
*1965-1980
*Integrated circuits
*OS: Multiprogramming
Fourth Generation:
*1980-present
*Large scale integration
*Personal computers
*OS: personal systems
Next Generation:
*????
*System connected to high
speed networks
*Wide area resource control
*OS: net-centric computing,
embedded systems.
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Simple Batch Systems
First real OS:
* OS was stored in one part of memory
* OS loaded a single job from a card reader into memory
* Ran that one job then loaded the next job.
* Cards told the OS what to do card reader
Early batch system
– bring cards to 1401
– read cards to tape
– put tape on 7094 which does computing
– put tape on 1401 which prints output
Memory layout
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Spooling( a future of third generation)
 Operating system reads jobs from cards onto disk instead
of reading directly into memory (reading is time consuming
so during reading some other jobs are also performed).
 Whenever a running job finished the operating system load
a new job from the disk into the now-empty partition and
run it.
 Spooling uses disk as a huge buffer e.g. storing output
files until the output devices are able to accept them.
 Overlap I/O of one job with computation of another job.
While executing one job, the OS:
o Reads next job from card reader into a storage area
on the disk (job queue).
o Outputs printout of previous job from disk to printer.
 Job pool – The sets of jobs.
 Spooling: Simultaneous Peripheral Operation on-line:
o Computer overlapped I/O of one job with execution of
another
o Still only one job active at any given time
o Reduces CPU idle time.
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Multi-programmed Batch Systems
 The operating system keeps several jobs in memory at a
time (known as job pool).The CPU is multiplexed (shared)
among them.
 The OS picks one job to be executed by CPU from
memory(jobs pool). The job may have to wait e.g. (I/O
task) for some tasks.
 When that job has to wait, OS switches to another job.
Eventually, the first job finishes waiting and gets the CPU
back.
 Multiple jobs in memory; all are protected from one
another.
• Multiprogramming system
– three jobs in memory – 3rd generation
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OS Features for Multi-programming:
 I/O routine supplied by the system.
 Memory management- the system must allocate the
memory to several jobs and should know their exact
locations.
 CPU Scheduling--the system must choose among several
jobs ready to run.
 Allocation of devices (other resources)
 Job scheduling mechanism is needed to know which job in
the job pool is to be loaded into memory
 Disk storage management
Time-Sharing Systems -- Interactive Computing
Each user has online terminal
 A time-shared OS uses CPU scheduling and multiprogramming that provides each user a small portion of a
time-shared computer. Each user executes his own
process.
 The CPU is multiplexed among several jobs that are kept
in memory and on disk (the CPU is allocated to a job only
if the job is in memory). The CPU is switched among
multiple jobs so frequently that the users may interact with
each program during execution.
 On-line communication between the user and the system
is provided; when the operating system finishes the
execution of one request / command, it seeks the next
“control statement” not from a card reader, but rather from
the user’s keyboard.
 Online system must be available for users to access data
 and code
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Personal Computer Systems
 Typically, in personal computers the computer system is
dedicated to a single user.
 May run several different types of operating systems
(Windows, Unix, Linux, MacOS, etc.)
Components of a simple personal computer
Parallel Systems
 Multiprocessor systems with more than one CPU in close
communication.
 Tightly coupled system- processors share memory and a
clock; communication among processors usually takes
place through the shared memory.
 Advantages of Parallel Systems:
o Increased throughput: more work done in the same
time period.
o Increasing processors by n does not mean
decreasing operation time by n.
o Economical: Since peripherals, power supplies are all
shared, several programs can be run on data on a
shared disk.
o Increased reliability:
 Fault tolerance: Failure of one processor does
not halt the system.
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Symmetric Multiprocessing (SMP)
 Each processor runs and identical copy of the operating
system. Each processor running a copy of the OS
communicate with each other as needed.
 Each processor can run any process.
 Many processes can run at once without performance
deterioration.
 Most modern OS’ s support SMP.
Asymmetric Multiprocessing (AMP):
 Each processor is assigned a specific task; master
processor schedules and allocates work to slave
processors.
 More common in extremely large Systems.
 Symmetric Multiprocessing (SMP)
Architecture:
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Operating System Concepts
Processes
Deadlocks
Memory Management
Input /Output
Files
Systems Calls
The interface between the operating system and the user
programs is defined by the set of system calls that the operating
system provides.
Metric Units
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