Operating System 2
Overview
OPERATING SYSTEM
OBJECTIVES AND FUNCTIONS
An OS is a program that controls the
execution of application programs and acts
as an interface between applications and the
computer hardware. Objectives:
 Convenience
 Efficiency
 Ability
to evolve
Briefly, the OS typically provides services in
the following areas:
 Program
development
 Program execution
 Access to I/O devices
 Controlled access to files
 System access
 Error detection and response
 Accounting
THE EVOLUTION OF
OPERATING SYSTEMS
Serial Processing
 Simple Batch Systems
 Multiprogrammed Batch Systems
 Time-Sharing Systems


Serial Processing
With the earliest computers, from the late 1940s to the
mid-1950s, the programmer interacted
directly with the computer hardware; there was no
OS.These computers were run
from a console consisting of display lights, toggle switches,
some form of input device,
and a printer. Programs in machine code were loaded via
the input device (e.g., a card
reader). If an error halted the program, the error condition
was indicated by the lights. If
the program proceeded to a normal completion, the output
appeared on the printer.

Simple Batch Systems

Multiprogrammed batch system

Time sharing
 single user was inefficient, a large group
of users together were not.
 the "state" of each user and their
programs would have to be kept in the
machine, and then switched between
quickly. Ex:
NEW — to name and begin writing a program
OLD — to retrieve a previously named program
LIST — to display the current program
SAVE — to save the current program
RUN — to execute the current program
Five major theoretical advances
1. Processes

A program in execution
 • An instance of a program running on a computer
 • The entity that can be assigned to and executed on a processor
 • A unit of activity characterized by a single sequential thread of execution, a
current state, and an associated set of system resources
•
•
Three major lines of computer system development created
problems in timing and synchronization that contributed to the
development of the concept of the process:multiprogramming batch
operation, time sharing, and real-time transaction systems
problems: Improper synchronization, Failed mutual exclusion,
Nondeterminate program operation, Deadlocks
Five major theoretical advances
2. Memory management
•
Process isolation
•
Automatic allocation and management
•
Support of modular programming
•
Support of modular programming
•
Long-term storage
Cont..
3. Information protection and security
•
•
•
•
Availability
Confidentiality
Data integrity
Authenticity
4. Scheduling and resource management\
•
•
•
Fairness
Differential responsiveness
Efficiency
5. System structure
MICROSOFT WINDOWS OVERVIEW
TRADITIONAL UNIX SYSTEMS
Modern Unix & Linux
System calls: The system
call is the means by
which a process
requests a specific
kernel service. There are
several hundred system
calls, which can be roughly
grouped into six
categories: filesystem,
process, scheduling,
interprocess
communication, socket
(networking), and
miscellaneous.Table 2.7
defines a few examples in
each category.
System calls: The system
call is the means by which a
process requests a specific
kernel service. There are
several hundred system calls,
which can be roughly
grouped into six categories:
filesystem, process,
scheduling, interprocess
communication,
socket (networking), and
miscellaneous.Table 2.7
defines a few examples
in each category.
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