Introduction #

Earlier you learned what an operating system is and why it exists. Now the real question is: what does the operating system actually do?

You don’t need to memorize a long list of functions.
What matters is understanding how the operating system keeps a computer working reliably when many things are happening at the same time.

This page explains the role of an operating system in a way that helps you build intuition, not just pass an exam.

The Operating System’s Core Job #

A computer has many parts CPU, memory, storage, input devices, displays, and more. When a program needs to use any of these parts, it does not talk to the hardware directly. Instead, it goes through the operating system.

In every modern computer system:

• The operating system accepts requests from applications
• It checks what’s allowed and safe
• Then it performs hardware operations on behalf of the application

This controlled coordination is the central role of an operating system. Without it, software would compete for resources, crash each other, and hardware would be chaotic.

Acting as a Resource Manager #

One of the best ways to think about the role of an operating system is as a manager of resources.

Imagine multiple applications running simultaneously:

• A browser
• A code editor
• A music player
• A file transfer

Each of these needs CPU time, memory, disk access, and I/O access such as network and keyboard. The operating system decides:

• Who gets what resource
• When they get it
• For how long

This is more than just allocation. The operating system:

• Prevents one program from overwriting another’s memory
• Ensures the CPU switches between tasks so everything appears to run at once
• Keeps track of which resources are in use and by whom

Providing Services Through Controlled Interfaces #

Applications need services like reading a file, creating a new process, or accessing the network. The operating system offers these through built-in interfaces called system calls.

System calls are the bridge between user space and kernel space:

• User space is where applications run
• Kernel space is where the operating system executes with full privileges

Applications use standard interfaces (like open, read, write or socket APIs) to ask the operating system to carry out complex or restricted operations on their behalf. (Wikipedia)

This ensures:

• Safety (programs can’t bypass rules)
• Portability (the same program works on different hardware)
• Protection (faulty or malicious programs can’t break system stability)

Hiding Hardware Complexity #

Hardware devices are diverse and complicated. Disk controllers, network cards, GPUs, keyboards — each has its own protocols and quirks.

The operating system hides this complexity by:

• Using device drivers to translate general requests into hardware-specific commands
• Providing uniform methods for applications to access devices

For example, reading from a file on any storage device usually feels the same to the application, even though the device hardware is very different.

This abstraction layer is a key role of the OS and enables the same application to work across different machines and configurations.

Enforcing Protection and Isolation #

A running program should not be able to:

• Read another program’s sensitive data
• Modify system code
• Crash the whole system

The operating system enforces isolation and protection between processes by:

• Preventing direct access to memory or hardware
• Restricting what system calls applications can make
• Managing permissions for files and devices

When an application misbehaves, the operating system can isolate or terminate it without affecting the rest of the system. This is crucial for reliability.

Supporting User Interaction #

Another important role of modern operating systems is to provide effective ways for users to interact with the system.

This includes:

• Command-line interfaces like Bash
• Graphical interfaces like GNOME, KDE, or desktop environments
• Keyboard, mouse, and touch input handling

The OS interprets user inputs and translates them into system actions or application behaviors forming the visible part of a computer system.

A Simple Mental Model #

If you visualize what an operating system does, it might look like this:

Applications
↓ (requests)
Operating System
↓ (controlled access)
Hardware

The operating system ensures that:

• Requests are validated
• Resources are shared fairly
• Hardware complexity is abstracted
• Security and isolation are maintained
• Users can interact with the system efficiently

Why This Matters for Linux #

In Linux, these roles are clearly expressed through components like:

• The kernel, which handles resource management
• System calls, which applications use to access services
• Device drivers, which abstract hardware differences

This consistent role model is why Linux scales from small embedded systems to massive servers, the operating system provides a stable and controlled environment for software on top of it.

Summary #

At a high level, the role of an operating system is to:

• Act as the intermediary between applications and hardware
• Manage shared resources like CPU, memory, and I/O
• Provide controlled services through system calls
• Abstract hardware complexity for developers
• Enforce protection and isolation
• Enable user interaction