Operating-Systems on P01NT

The Basic Structure of Operating Systems

Tue, 25 Aug 2026 22:00:00 +0300

بسم الله

Peace be upon you. Today I would like to talk with you about the structural foundation of operating systems in general, attempting to cover the following points:

The Von Neumann architecture.
The central tasks of an operating system (OS Central Tasks).

Let us begin.

What Is an Operating System?

Everyone living in this modern, technology-rich age has dealt with an operating system one way or another, and everyone has heard the term “Operating Systems” or “OS”. But!

Introduction to Operating Systems

Tue, 25 Aug 2026 23:00:00 +0300

بسم الله

Peace be upon you.

This series will cover the following topics:

Processes.
Memory Management.
File Systems.
Scheduling.
Interrupts.

As usual, this series will not be dull theory alone; it will include practical examples in C and diagrams to aid understanding. I wanted to lay out what you will take from this series so readers know what awaits them. May God grant success and guidance.

It is recommended before starting this series to go through the Computer Architecture & Organization series on the blog.

Interrupts

Tue, 25 Aug 2026 23:30:00 +0300

بسم الله

Having learned about the structure of operating systems, this article will — God willing — serve as your reference for understanding interrupts.

Our method in this series is to tie examples to the terms and concepts we take on, and you will find illustrative images and code to deepen understanding.

Computer-System Organization

Before diving into our subject, we must understand how a computer system is organized — main concepts do not stand without foundations to build understanding upon; no one sells fish to someone standing on the seashore.

Processes & Threads

Wed, 26 Aug 2026 00:00:00 +0300

بسم الله

This article is dedicated to Processes & Threads, which exist in every operating system.

Processes

Briefly, a process is a program in execution.

A process has a structure inside the kernel called KProcess, or the Process Control Block (PCB), which the kernel uses to control this process’s operations.

The PCB contains many fields; the most important:

Process State: the state of the process.
Process Number: the process’s number.
Program Counter: the program counter.
Registers: the registers belonging to the process.

Figure (1): The process control block

Scheduling

Wed, 26 Aug 2026 00:30:00 +0300

بسم الله

In this article we will talk about process scheduling in general.

Process Types

If we have more than one process sitting in memory, how does the operating system execute them?

First we must know that processes come in types:

1. I/O-Bound Processes: Processes that request input/output frequently (like reading files), spending much of their time waiting for I/O to complete.

2. CPU-Bound Processes: Processes that consume a large amount of processor time and rarely require input/output (like complex computations).

Memory Management

Wed, 26 Aug 2026 00:45:00 +0300

بسم الله

After talking about scheduling in the previous lesson, today we move to one of the pillars of operating systems: main memory management. We already touched a practical side of it in the virtual memory lesson of the C workshop; this lesson is the theoretical foundation it all rests on.

Background

A modern OS must allow large numbers of processes to sit in memory simultaneously for concurrent execution — and that is what makes memory management complex. There is quite a range of memory-management algorithms, and most require special forms of hardware support.

File-System Interface

Wed, 26 Aug 2026 01:30:00 +0300

بسم الله

Having finished memory management in the previous lesson, this lesson concludes the series: the File-System Interface.

File system implementation is a major aspect of operating system architecture: designers must decide how to map file-system information onto physical storage devices, and what methods to provide for accessing and manipulating it. File systems are often performance bottlenecks — making them adequately efficient is quite a challenge.

A file system consists of two parts: a collection of files, and a directory structure whose purpose is providing information about, and organization of, those files.