Introduction #

To understand why an operating system is required, it helps to think about what happens without one.

A computer is just hardware.
CPU, memory, disk, keyboard, display all of them are useless unless someone controls how they are used.

Now imagine writing a program that directly talks to the hardware.

The program would need to:

• Decide when it can use the CPU
• Know which memory locations are free
• Handle input from keyboard or mouse
• Write data to disk without corrupting other data
• Deal with hardware errors and interrupts

Doing this once is hard.
Doing this for every program is impossible.

This is the main reason an operating system exists.

Problem 1: Multiple Programs Cannot Run Safely #

Modern systems always run more than one program:

• A browser
• A text editor
• Background services
• System utilities

If all programs try to use the CPU and memory directly:

• One program can overwrite another program’s memory
• A bug in one program can crash the entire system
• No program knows when to stop or wait

The operating system solves this by:

• Giving each program its own execution context
• Controlling how long a program runs on the CPU
• Isolating memory between programs

Problem 2: Hardware Is Too Complex #

Hardware is not simple to use directly.

Different systems have:

• Different CPUs
• Different storage devices
• Different network hardware
• Different input devices

If applications had to handle hardware directly, the same program would need to be rewritten for every machine.

The operating system hides this complexity.

Programs do not care:

• How a disk controller works
• How data is transferred on a network
• How interrupts are handled internally

They ask the operating system to do it for them.

Problem 3: No Resource Management #

CPU time, memory, disk space, and devices are limited resources.

Without an operating system:

• One program can consume all CPU time
• Memory can be allocated and never freed
• Devices can be locked forever by a single program

The operating system acts as a manager:

• It schedules CPU usage
• It allocates and frees memory
• It controls access to devices
• It enforces limits and priorities

Problem 4: No Security or Protection #

Without an operating system:

• Any program can read any memory
• Any program can modify system data
• Malicious code has full control

An operating system introduces protection:

• User mode vs privileged mode
• Controlled access to hardware
• Permission checks for files and processes

Even a small mistake in a program does not bring the whole system down.

Problem 5: No Standard Way to Write Programs #

Without an OS, every program would need to:

• Handle hardware directly
• Implement its own scheduling logic
• Manage its own memory
• Control devices manually

This makes software development slow and error-prone.

The operating system provides standard services:

• Process creation
• File handling
• Memory allocation
• Communication between programs

Programmers write application logic, not hardware control logic.

Why This Matters for Embedded and Linux Systems #

In embedded systems, some very small applications can run without an OS.
But as soon as the system needs:

• Multitasking
• Timers
• Communication
• Predictable behavior

An operating system becomes necessary.

Linux uses the same ideas but scales them from small devices to servers.

That is why understanding why an OS is required is more important than memorizing definitions.

Summary #

An operating system is required because:

• Hardware alone cannot manage itself
• Multiple programs need controlled execution
• Resources must be shared safely
• Hardware complexity must be hidden
• Security and protection are necessary
• Software needs standard interfaces

Without an operating system, modern computers and Linux systems simply cannot function in a reliable way.