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Chapter 2
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What is the primary role of an operating system (OS)?
OS is a program interface between applications and hardware, controls application program execution.
What are the three main objectives of an operating system?
Convenience, efficiency, ability to evolve.
List some functions of an operating system related to program development and execution.
Program development, program execution, access IO devices.
What is the role of an operating system in managing resources in a computer system?
The OS is responsible for managing the resources for the movement, storage, and processing of data.
What is a function in terms of computer software?
A program or suite of programs executed by the processor that frequently relinquishes control and depends on the processor to allow it to regain control.
What are some reasons for the evolution of operating systems over time?
Hardware upgrades, new types of hardware, new services, and fixes are some reasons for the evolution of operating systems.
What are the stages in the evolution of operating systems?
The stages include serial processing, simple batch systems, multiprogrammed batch systems, and time-sharing systems.
Describe the characteristics of serial processing in the context of operating systems.
In serial processing, computers ran without an operating system, programmers interacted directly with the hardware, and users accessed the computer in series.
What were the problems associated with serial processing in early computers?
Problems included scheduling difficulties, where time allocations could run short or long resulting in wasted computer time, and setup time spent on setting up programs to run.
What were the characteristics of simple batch systems in the evolution of operating systems?
In simple batch systems, computers were expensive, users no longer had direct access to the processor, and jobs were submitted to a computer operator who batched them together.
What was the role of the monitor in a simple batch system?
The monitor in a simple batch system maximized processor utilization by queuing jobs and routing them to the processor when available.
What is the purpose of setting up Simple Batch Systems?
To maximize processor utilization and save costs on early expensive computers.
In Simple Batch Systems, who monitors user activities?
The computer operator, as users no longer have direct access to the processor.
What happens to a job after it is submitted in a Simple Batch System?
The job is batched together with other jobs by the computer operator and placed on an input device.
What occurs when a program finishes execution in a Simple Batch System?
The program branches back to the monitor for further monitoring and control.
What is a Resident Monitor responsible for?
Controlling the sequence of events and always staying in memory
What does the Monitor do after reading in a job?
It gives control to the job
What happens after a job returns control to the Monitor?
The processor executes instructions from the memory containing the monitor
What happens when the processor encounters an ending or error condition in a user program?
Control is passed back to the job
When control is returned to the monitor, what is the processor doing?
Fetching and executing instructions from the monitor program
What is JCL (Job Control Language)?
A special type of programming language used to provide instructions to the monitor
What is the purpose of Memory Protection for the monitor?
To prevent a job from monopolizing the system and ensure user program execution does not alter the monitor's memory area
What can only be executed by the monitor?
Timer
What do Privileged instructions allow the OS to do?
Have more flexibility in controlling user programs
What are the two Modes of Operation?
User Mode and Kernel Mode
In which mode does a user program execute?
User Mode
What restrictions are there in User Mode?
Certain areas of memory are protected from user access and certain instructions may not be executed
In which mode does the monitor execute?
Kernel Mode
What is allowed in Kernel Mode?
Execution of privileged instructions and accessing protected areas of memory
What is User Mode in operating systems?
User program executes in user mode, certain areas of memory are protected from user access, and certain instructions may not be executed.
