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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