Hardware & OS: Overview
Hardware & OS: Overview
This page introduces the basic model of a computer and explains how the hardware and the operating system interact. It provides the mental map for the following pages.
What is a Computer Built Of?
A computer can be very simple (a microcontroller in an electric toothbrush) or highly complex (a multi-CPU server). In both cases, the core elements are the same:
- Central Processing Unit (CPU): executes instructions (computation, comparison, data movement).
- Memory: stores instructions and data.
- Peripherals: devices for input, output, and storage (keyboard, display, disk, network, USB, …).
- Minimal model → CPU + memory.
- Extended model → CPU + memory + peripherals.
Memory as “Remembered State”
The essential feature of memory is to store information until changed.
- Everyday metaphor: a light switch remains on or off until someone flips it.
- In computers: states are represented electrically (voltage = 1, no voltage = 0).
- Changing state = overwriting a previous value.
This idea underlies all later forms of computer memory, from punch cards to DRAM.
The CPU at a Glance
The CPU is often described as the “brain” of the computer. Its core tasks:
- Arithmetic (addition, subtraction, logic).
- Comparisons (greater/less/equal).
- Moving data (load from memory, store to memory).
- Controlling execution flow (jumps, calls).
Modern systems blur boundaries: A graphics processor (GPU) or a network card may include their own CPUs for specialized tasks.
Why the Operating System Exists
Without an OS, a program would have to:
- Control every piece of hardware directly,
- Handle memory layout itself,
- Decide which program runs when.
The OS solves this by:
- Acting as a resource manager (CPU time, memory, I/O).
- Providing abstractions (files, processes, devices).
- Enabling multitasking and multi-user operation.
Putting It Together
A working system typically looks like this:
[ Peripherals ] ↔ [ CPU ] ↔ [ Memory ]
↑
[ Operating System ]
- Hardware provides the raw capabilities.
- The OS organizes and controls access.
- Programs run *on top of* the OS, not directly on the hardware.