Complete Guide to Operating Systems | OS Basics, How They Work, Multitasking, 32-bit vs 64-bit, Windows, Linux Overview
An operating system (OS) is the core system that connects a computer’s hardware and software, efficiently managing resources such as the CPU, memory, and storage.
It provides users with both console and GUI environments, allowing anyone to easily communicate with the computer, while also supporting multitasking so multiple programs can run at the same time.
There are various kinds of operating systems, including Windows, Linux, macOS, iOS, and Android. Each has its own characteristics, advantages, and disadvantages, and is used in both PC and mobile environments depending on those traits.
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In the previous series, we looked at the physical structure of computers. This time, we will examine the operating system.
When you turn on a computer, the very first thing that runs is the operating system. Although it is invisible, it acts like an unseen manager that allows us to freely use the computer. Even simple actions such as clicking an icon with the mouse or typing a letter on the keyboard would be impossible without the OS.
For example, when you press “A” on the keyboard, the electrical signal is sent to the CPU, transformed into a character code, and displayed as the letter “A” on the monitor. This entire process is coordinated by the operating system.
To understand the role of the OS, we must first recall the difference between hardware and software.
Hardware refers to the computer’s physical parts that you can see and touch, such as the CPU, memory, and graphics card, as explained in previous articles. Software, on the other hand, is not physical but consists of the programs running on the hardware—for instance, games, web browsers, and document editors.
The operating system acts as a bridge between the two, providing a standardized environment so users do not have to deal with hardware directly.
Without an OS, a user would have to send commands directly to the hardware. For example, to save a file, one would need to know the detailed instructions for the storage device, and to display text on the screen, one would have to understand exactly how the graphics card functions. With the OS handling these complex processes in the background, the user only needs to run a program and click a button. The OS allocates and manages the CPU, memory, storage, and input/output devices so that resources are used efficiently.
The OS also provides the interface that lets users interact with computers.
In the past, text-based consoles required users to type commands manually. Today, graphical user interfaces (GUIs) with icons and windows are widely used. The Windows taskbar and the touchscreens of smartphones are examples of user-friendly interfaces developed by operating systems. Thanks to this, even those who don’t know complex commands can easily use computers.
Multitasking is another important feature.
In reality, a CPU can only perform one task at a time. But the OS divides CPU time into very small slices and allocates them to multiple programs in turn, making it appear as if they are running simultaneously. Watching a video in a browser, listening to music, and editing a document at the same time is possible because the OS uses time-sharing to distribute resources effectively.
There is also the concept of 32-bit and 64-bit operating systems.
Here, “bit” refers to the size of data that can be processed at once. A 32-bit OS allows the CPU to handle 32 bits at a time and can recognize up to about 4GB of memory. Even if 8GB or 16GB of RAM is installed, only part of it can actually be used.
A 64-bit OS, however, can handle 64 bits at once, which allows it to use much larger memory spaces—up to terabytes in theory. Beyond just larger memory capacity, 64-bit systems also provide better efficiency and stronger security features. For example, 64-bit programs can process larger data units in a single calculation, and security technologies such as ASLR are more robust.
Most modern operating systems are based on 64-bit architecture, while 32-bit systems are now mostly found on older hardware or embedded devices. For new computers and installations, 64-bit has effectively become the standard.
Looking at the history of operating systems: Unix emerged in the 1960s and became the foundation of modern OS design. In the 1980s, MS-DOS and Windows advanced, opening the era of personal computers. The 1990s saw the rise of Linux and the spread of the open-source movement. Since the 2000s, iOS and Android have driven the mobile OS era. In this development process, large companies like Microsoft, Apple, and Google, as well as open-source communities, have all played major roles.
Today, virtualization is also an important concept. Virtualization means running multiple operating systems simultaneously on a single physical computer. For example, you can run Linux in a virtual machine inside Windows. (This will be covered in detail in another article later.)
Even at the moment you click a program icon, the OS is at work. It loads the program into memory, instructs the CPU to perform calculations, reads necessary data from storage, and sends the results to the monitor and speakers. In other words, the OS is responsible for the entire process of program execution.
For those who want to study operating systems more deeply, recommended textbooks include Operating System Concepts (often called the “Dinosaur Book”) and Andrew S. Tanenbaum’s Modern Operating Systems. These are widely used in universities and help build a systematic understanding of OS principles.
In the end, the operating system is the invisible manager and resource allocator of the computer. Whether we are playing games, writing documents, or browsing the web, the OS is constantly working in the background to make everything possible. Understanding its existence and principles is the first step toward a deeper understanding of IT.
That concludes this overview of operating systems. In the next article, we will examine the specific characteristics of Windows, Linux, macOS, iOS, and Android in more detail.
Thank you for reading, and have a great day!
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