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:

ConvenienceEfficiencyAbility to evolve

Briefly, the OS typically provides services in the following areas:

Program developmentProgram executionAccess to I/O devicesControlled access to filesSystem accessError detection and responseAccounting

THE EVOLUTION OF OPERATING SYSTEMS

Serial Processing Simple Batch Systems Multiprogrammed Batch Systems Time-Sharing Systems

Serial ProcessingWith the earliest computers, from the late 1940s to the mid-

1950s, the programmer interacteddirectly with the computer hardware; there was no

OS.These computers were runfrom 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 cardreader). If an error halted the program, the error condition

was indicated by the lights. Ifthe 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 programOLD — to retrieve a previously named programLIST — to display the current programSAVE — to save the current programRUN — 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 specifickernel 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 specifickernel service. There are several hundred system calls, which can be roughlygrouped into six categories: filesystem, process, scheduling, interprocess communication,socket (networking), and miscellaneous.Table 2.7 defines a few examplesin each category.

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