Chapter 2
Operating System
Overview
Western Illinois University
Computer Science
Antonio Cardenas
Operating
Systems:
Internals
and Design
Principles CS 410
Operating Systems
Operating System
■ A program that controls the execution of
application programs
■ An interface between applications and
hardware
Operating System Services
■ Program development
■ Program execution
■ Access I/O devices
■ Controlled access to files
■ System access
■ Error detection and response
■ Accounting
Key Interfaces
■ Instruction set architecture (ISA)
■ Application binary interface (ABI)
■ Application programming interface
(API)
The Role of an OS
■ A computer is a set of resources for
the movement, storage, and
processing of data
■ The OS is responsible for managing
these resources
Operating System
as Software
■ Functions in the same way as ordinary
computer software
■ Program, or suite of programs,
executed by the processor
■ Frequently relinquishes control and
must depend on the processor to allow
it to regain control
Serial Processing
Earliest Computers:
■ No operating system
■ programmers interacted
directly with the
computer hardware
■ Computers ran from a
console with display lights,
toggle switches, some form of
input device, and a printer
■ Users have access to the
computer in “series”
Problems:
■ Scheduling:
■ most installations used a
hardcopy sign-up sheet to
reserve computer time
■ time allocations
could run short or
long, resulting in
wasted computer
time
■ Setup time
■ a considerable amount of
time was spent just on
setting up the program to
run
Evolution of Operating Systems
▪A major OS will evolve over time for
a number of reasons:
Uniprogramming
■ The processor spends a certain amount
of time executing, until it reaches an I/O
instruction; it must then wait until that
I/O instruction concludes before
proceeding
Multiprogramming
■ There must be enough memory to hold the OS (resident
monitor) and one user program
■ When one job needs to wait for I/O, the processor can
switch to the other job, which is likely not waiting for I/O
Multiprogramming
■ Multiprogramming
■ also known as multitasking
■ memory is expanded to hold three, four, or more
programs and switch among all of them
Multiprogramming
Example
Table 2.1 Sample Program Execution Attributes
Effects on Resource
Utilization
Table 2.2 Effects of Multiprogramming on Resource Utilization
Time-Sharing Systems
■ Can be used to handle multiple interactive
jobs
■ Processor time is shared among multiple
users
■ Multiple users simultaneously access the
system through terminals, with the OS
interleaving the execution of each user
program in a short burst or quantum of
computation
Major Achievements
■ Operating Systems are among the most
complex pieces of software ever
developed
Causes of Errors
■ Nondeterminate
program operation
■ program execution is
interleaved by the
processor when memory
is shared
■ the order in which
programs are scheduled
may affect their outcome
■ Deadl
ock
s
■ it is possible for two or
more programs to be
hung up waiting for each
other
■ may depend on the
chance timing of resource
allocation and release
■ Improper
synchronization
■ a program must wait until
the data are available in a
buffer
■ improper design of the
signaling mechanism can
result in loss or
duplication
■ Failed mutual
exclusion
■ more than one user or
program attempts to
make use of a shared
resource at the same
time
■ only one routine at a
time allowed to perform
an update against the file
Components of
a Process
■ The execution
context is essential:
■ it is the internal data by
which the OS is able to
supervise and control
the process
■ includes the contents
of the various process
registers
■ includes information
such as the priority of
the process and
whether the process is
waiting for the
completion of a
particular I/O event
■ A process contains
three components:
■ an executable program
■ the associated data
needed by the program
(variables, work space,
buffers, etc.)
■ the execution context
(or “process state”) of
the program
Virtual Memory
■ A facility that allows programs to address
memory from a logical point of view,
without regard to the amount of main
memory physically available
■ Conceived to meet the requirement of
having multiple user jobs reside in main
memory concurrently
Paging
■ Allows processes to be comprised of a number of
fixed-size blocks, called pages
■ Program references a word by means of a virtual
address
■ consists of a page number and an offset within the
page
■ each page may be located anywhere in main memory
■ Provides for a dynamic mapping between the virtual
address used in the program and a real (or physical)
address in main memory
Information Protection
and Security
■ The nature of the threat that concerns an
organization will vary greatly depending on the
circumstances
■ The problem involves controlling access to
computer systems and the information stored in
them
Different Architectural
Approaches
■ Demands on operating systems require
new ways of organizing the OS
Fault Tolerance
■ Refers to the ability of a system or component to
continue normal operation despite the presence of
hardware or software faults
■ Typically involves some degree of redundancy
■ Intended to increase the reliability of a system
■ typically comes with a cost in financial terms or
performance
■ The extent adoption of fault tolerance measures must be
determined by how critical the resource is
Table 2.4
Availability Classes
Availability Classes
Fault Categories
■ Permanent
■ a fault that, after it occurs, is always present
■ the fault persists until the faulty component is replaced or repaired
■ Temporary
■ a fault that is not present all the time for all operating conditions
■ can be classified as
■ Transient – a fault that occurs only once
■ Intermittent – a fault that occurs at multiple, unpredictable times
Traditional UNIX Systems
■ Were developed at Bell Labs and became operational on a PDP-7 in 1970
■ Incorporated many ideas from Multics
■ PDP-11 was a milestone because it first showed that UNIX would be an OS
for all computers
■ Next milestone was rewriting UNIX in the programming language C
■ demonstrated the advantages of using a high-level language for
system code
■ Was described in a technical journal for the first time in 1974
■ First widely available version outside Bell Labs was Version 6 in 1976
■ Version 7, released in 1978 is the ancestor of most modern UNIX systems
■ Most important of the non-AT&T systems was UNIX BSD (Berkeley
Software Distribution)
LINUX Overview
■ Started out as a UNIX variant for the IBM PC
■ Linus Torvalds, a Finnish student of computer science, wrote the
initial version
■ Linux was first posted on the Internet in 1991
■ Today it is a full-featured UNIX system that runs on several
platforms
■ Is free and the source code is available
■ Key to success has been the availability of free software packages
■ Highly modular and easily configured
Modular
Monolithic Kernel
■ Includes virtually all of the OS
functionality in one large
block of code that runs as a
single process with a single
address space
■ All the functional
components of the kernel
have access to all of its
internal data structures and
routines
■ Linux is structured as a
collection of modules
Loadable Modules
■ Relatively independent
blocks
■ A module is an object file
whose code can be linked to
and unlinked from the kernel
at runtime
■ A module is executed in
kernel mode on behalf of the
current process
■ Have two important
characteristics:
■ dynamic linking
■ stackable modules
Table 2.6 Some
Linux Signals
Linux Signals
Power Management
Alarms
■ Implemented in the Linux
kernel and is visible to the
app developer through the
AlarmManager in the
RunTime core libraries
■ Is implemented in the kernel
so that an alarm can trigger
even if the system is in sleep
mode
■ this allows the system to
go into sleep mode,
saving power, even
though there is a
process that requires a
wake up
Wakelocks
■ Prevents an Android system
from entering into sleep
mode
■ These locks are requested
through the API whenever an
application requires one of
the managed peripherals to
remain powered on
■ An application can hold one
of the following wakelocks:
■ Full_Wake_Lock
■ Partial_Wake_Lock
■ Screen_Dim_Wake_Loc
k
■ Screen_Bright_Wake_L
ock
Summary
■ Operating system objectives
and functions
■ User/computer interface
■ Resource manager
■ Evolution of operating
systems
■ Serial processing
■ Simple/multiprogrammed/ti
me-sharing batch systems
■ Major achievements
■ Developments leading to
modern operating systems
■ Fault tolerance
■ Fundamental concepts
■ Faults
■ OS mechanisms
■ OS design considerations for
multiprocessor and multicore
■ Microsoft Windows overview
■ Traditional Unix systems
■ History/description
■ Modern Unix systems
■ System V Release 4 (SVR4)
■ BSD
■ Solaris 10
■ Linux
■ History
■ Modular structure
■ Kernel components
■ Android
■ Software/system architecture
■ Activities
■ Power management
CS 410 Operating Systems
Homework 02
Review Questions (7 pts/ea)
2.1 What are three objectives of an OS design?
2.2 What is the kernel of an OS?
2.3 What is multiprogramming?
2.4 What is a process?
2.5 How is the execution context of a process used by the OS?
2.6 List and briefly explain five storage management responsibilities of a typical OS.
2.7 Explain the distinction between a real address and a virtual address.
2.8 Describe the round-robin scheduling technique.
2.9 Explain the difference between a monolithic kernel and a microkernel.
2.10 What is multithreading?
2.11 List the key design issues for an SMP operating system.
Problems: (8 pts the first two, 7 points the last one)
2.2 An I/O-bound program is one that, if run alone, would spend more time waiting for
I/O than using the processor. A processor-bound program is the opposite. Suppose a
short-term scheduling algorithm favors those programs that have used little processor
time in the recent past. Explain why this algorithm favors I/O-bound programs and
yet does not permanently deny processor time to processor-bound programs.
2.3 Contrast the scheduling policies you might use when trying to optimize a time-sharing
system with those you would use to optimize a multiprogrammed batch system.
2.4 What is the purpose of system calls, and how do system calls relate to the OS and to
the concept of dual-mode (kernel-mode and user-mode) operation?
SUBMISSION
Submit a DOCX or PDF document through Western Online with the answers to the questions or
problems typing the corresponding numbers and questions (or at least the numbers) in bold
and in the proper order before your answers.
Use a different font color for the numbers and questions (or at least for the numbers), than the
color used for your answers.
—–///
Order an Essay Now & Get These Features For Free:
Turnitin Report
Formatting
Title Page
Citation
Outline
