Download Operating Systems

Review:
CS100: Introduction to
Computer Science
n
Arithmetic/Logic Operations
Logic: AND, OR, XOR
q
n
q
Lecture 8: Operating System
n
Communicating with other devices
Controller,
q
n
n
Chapter 3: Operating Systems
n
3.1 The History of Operating Systems
n
3.2 Operating System Architecture
n
3.3 Coordinating the Machine’s Activities
n
An operating system: the software that
controls the overall operation of a computer.
q
q
q
Operating Systems
UNIX
q
Originally developed by AT&T in 1960s
Popular in large computer systems.
DOS
q
1981—1997 by IBM
q
Used PCs
Windows (1985 -- now)
q
By Microsoft,
q
Add Graphical User interface to DOS systems
q
Wildly used in PCs
LINUX (1980s – now)
q
UNIX-like operating systems
q
A free software., source code is available for anyone to use and
modify
n
n
Provides the means for a user to store and
retrieve files
Provides the interface for a user to request the
execution of a program
Coordinates the execution of programs
…
Evolution of Shared Computing
n
q
n
Specialized controllers for each type of device
General purpose controllers: USB, FireWire
Functions of Operating Systems
q
n
Masking
Rotate and Shift: circular shift, logical shift, arithmetic shift
Arithmetic: add, subtract, multiply, divide
q
n
Batch processing
q
Collecting jobs in a single batch and then execute them without further
interaction with the user.
Interactive processing
q
Allows a program being executed to carry on a dialogue with the user
through remote terminals
q
n
Requires real-time processing
Time-sharing/Multitasking
n
n
n
n
More tasks being performed at the “same time” or serve more users at the
“same time”
Time-sharing system: divide time into intervals, jobs takes turns to use
CPU time.
Provide reasonable real-time processing for each user.
Multiprocessor machines
q
Assign different tasks to different processors
1
Figure 3.1 Batch processing
Types of Software
n
q
Performs specific tasks for users
Database systems, games, program developing software,
etc.
System software
q
q
q
Provides infrastructure for application software
Consists of operating system and utility software
Utility software: programs for performing fundamental
activities, but not included in operating systems.
n
E.g data compression software, network communication
software.
Operating System Components
n
Figure 3.3 Software classification
Application software
q
n
Figure 3.2 Interactive processing
Shell: interface between users and the internal part
(kernel)of operating systems.
q
q
Figure 3.4 The shell as an interface
between users and
the operating system
Text based
Graphical user interface (GUI)
n
Window manager: allocates block of space on the screen,
keeps track of which application is associated with each
window.
n
Kernel: Performing basic required functions
n
Allows different shells to access the same kernel
2
Operating System Components
n
n
Shell: interface between users and the internal part
of operating systems.
Kernel: Performing basic required functions
q
q
q
q
File manager
Device drivers
Memory manager
Scheduler and dispatcher
File Manager
n
Coordinates the use of mass storage devices
q
Maintain records of all files
n
q
n
Directory (or Folder): A user-created bundle of files
and other directories (subdirectories)
n
Directory Path: A sequence of directories within
directories
n
n
Device Drivers
n
n
Software units that communicate with the controllers
to carry out operations on the peripheral devices.
n
Allocates space in main memory
n
May create the illusion that the machine has more memory than
it actually does (virtual memory) by playing a “shell game” in
which blocks of data (pages) are shifted back and forth between
main memory and mass storage
Each device driver is uniquely designed for its
particular type of device and translate the generic
requests to more technical steps required by the
device
q
512MB main memory, 1024MB virtual memory
n
n
Printer drive, disk drive
Scheduler and Dispatcher: Processes
n
n
Process: The activity of executing a program
Process State: Current status of the activity
q
q
q
n
Value in program counter: the current position in the
program being executed
Values in general purpose registers:
Associated memory cells
Process Table: store information of processes
q Memory area assigned to a process
q
q
The priority of the process
Whether the process is ready or waiting
courses/cs100/slides on UNIX
courses\cs100\slides on WINDOWS
Memory Manager
n
n
Where a file is stored, which users are allowed to access it
Records are kept on the individual storage medium
containing the related files.
n
Reserve 1024MB on a magnetic disk and store bit patterns there.
Data are divided into pages.
Transfer pages into main memory if information are needed soon.
Transfer pages back into the disk if information will not be needed in
short time.
Process Administration
n
Scheduler: Adds new processes to the
process table and removes completed
processes from the process table
n
Dispatcher: Controls the allocation of time
slices to the processes in the process table
q
The end of a time slice is signaled by an interrupt.
q
3
Figure 3.6 Time-sharing between
process A and process B
How Does An Operating System Get
Started (Bootstrapping/booting)
n
ROM: read-only memory
q
q
n
Bootstrap: the program stored in ROM
q
q
q
q
Figure 3.5 The booting process
A portion of main memory but constructed from non-volatile
memory cells.
Its contents can be read but not altered.
Run by the CPU when power is turned on
Transfers operating system from mass storage to main
memory
Executes jump to operating system
The operating system then takes over and begins
controlling the machine’s activity.
Questions:
n
List the components of a typical operating
system and explain the role of each.
n
Summarize the booting procedure.
n
What is the difference between a process
and a program?
Announcements:
n
Next lecture: Review Session
n
Monday, March 5th : first in-class exam
4