The OS structure - Access 2 Learn

The modern OS is a complex structure comprised of millions of lines of code. Not all information is released, and is this core components, or everything including additional apps that have been included?

Mac OS X Tiger (10.4) ~ 84 Million Lines of Code
Windows Vista (2009) ~50 Million Lines of Code
Debian 7.0 (2012) ~419 Million Lines of Code

The kernel of an OS is the minimal set of functions necessary to manage the system resources safely and efficiently. The kernel provides the most essential of services for the OS.

The CPU is divided into two sets: privileged and non-privileged. A privileged instruction performs critical operations. Only the OS kernel is allowed to execute privileged instructions.

A system call is a request from an application for an OS service.

The OS structure was originally found on Access 2 Learn

Walter Wimberly

Assistant Professor

Walter Wimberly is an Assistant Professor at a regional college in Tennessee, teaching Computer Science in the Software Engineering track. He works as a student advisor, oversees curriculum changes, develops new courses, and manages the advisory panel.
Walter taught full time for about 7 years, before going back into “industry” as a full stack Software Developer for a dozen years. There he focused on web based projects coding in JavaScript/jQuery and utilizing the Bootstrap CSS Framework on the front-end, and coding in PHP, ASP/ASP.Net, SQL on the back-end.

Since he loves teaching, he taught as an adjunct web and digital media classes for eight (8) years, while working in industry, and has since returned to teaching full time.

He has been married for over 25 years, and is father to several special needs boys. As such, he is working on some projects to help others who have special needs to be self-sufficient, and support the care givers of those with special needs. Check out his Autism blog for more info.

Operating Systems

System Resources

ByWalter Wimberly September 9, 2020September 10, 2020

The OS has to track resources so that it knows when those resources are available for use. If it “just let” processes use resources, they could step on the resources and crash the system as a resource can only be used by a single process at a time. So the OS uses an Resource Control…

Operating Systems

The Implementation of Semaphores

ByWalter Wimberly September 21, 2020September 21, 2020

Most contemporary computer architectures offer hardware support for process synchronization in the form of specialized machine instructions. The test-and-set instruction (TS) copies a variable into a register and sets the variable to zero in one indivisible machine cycle. Test-and-set has the form TS(R, x) where R is a register and x is a memory location and performs…

Operating Systems | Tips

Using an OS – Part 2

ByWalter Wimberly August 26, 2020August 26, 2020

In part 1 of Using an OS, we looked at user management, basic security, and file explorer. While Windows has made it easier to store files logically, it is still up to the user. Too often I’ve seen people with hundreds of files on their desktop. Often there, just “temporarily” until they no longer need…

Operating Systems

The Purpose of the Operating System

ByWalter Wimberly August 19, 2020August 19, 2020

At the highest level, the operating system (OS) is a piece of software that is there to manage all of the software and hardware of the computer. It is not generally considered to be a single program, but a series of programs and utilities that can make this happen. Most of the time, in a…

Operating Systems

Principles of Scheduling

ByWalter Wimberly September 14, 2020September 14, 2020

Long-term scheduling decides when a process should enter the ready state and start competing for the CPU. It also manages those which are suspended, to acknowledge when they are ready to move to the ready list. Short-term scheduling decides which of the ready processes should run next on the CPU. Most processes move because of the short…

Operating Systems

Access Control

ByWalter Wimberly November 17, 2020November 17, 2020

A computer system consists of a set of hardware and software objects. The protection domain is a set of pairs of objects and rights needed to access those objects. An access matrix is a representation of protection domains. (It is more conceptual than actual however.) Each row specified the object, and a right that can be performed as…

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