FATOS Chapter 2 The Fundamentals

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Initial Observations

A computer system is made up of hardware and software.

Hardware includes electronics, chips, circuit boards, cables, and connectors. Peripherals are devices we connect to the computer, and include hardware such as a monitor, keyboard, mouse, touch-screen, printer, to enable us to input and output information.

Computers require electricity to work – like any machine it uses power and generates heat. The electricity moves through digital electronic circuits, using voltage to create binary signals by turning ‘switches’ on and off. How fast a computer is depends on how fast the electricity moves through these circuits, because it takes time for the signals to move through the system. Speed is an important factor in computers, and technology has evolved to make processors evermore powerful.

Software

The term ‘software’ are instructions that your computer processes to complete a task. The Operating System, or OS, is software. You will probably know this as Windows, macOS, or Linux, though there are others. Operating Systems make it easier for users to perform tasks using a computer.

Software includes applications, such as word processors, utilities, part of the operating system, such as Task Manager, compilers, interpreters, firmware, browser programs such as JavaScript that makes websites work, and even viruses. We will go into these different types of software later.

Computer Specs

Computers work on a microscopic scale, and due to this, there are certain units we use to measure distance, speed and time:

  • Power is measured in watts: milliwatts, microwatts, and nanowatts.
  • Frequency is measured in megahertz and gigahertz. Frequency is the term used for operations performed by the computer per second. These are huge numbers, hence the use of mega and giga.
  • The computer’s clock is measured in Hertz. It is a pulse that regulates the computer system, like a heart beat in the human body.
  • Data capacity is measured in bytes. We know that a bit is a single value: a 1 or a 0. A byte is a group of 8 bits. Modern computer systems have capacities measured in kilobytes, megabytes, and gigabytes. Some top-of-the-range computers and mass storage devices use terabytes.
  • Data rate is how much data can be transferred in one second. This is measured in bytes per second, for example megabytes per second would be documented as Mb/s.
  • Processor speed is represented in MIPS: millions of instructions per second.

Like cars, different types of computers have different specifications. One car may be faster than another – this is the same as computers. You can install specialist parts to upgrade your car – you can also do this for computers.

Discussing how fast a car goes is easy to understand – it can reach 60 mph in 10 seconds. How fast data is transferred from one component to another is a bit more tricky: we use the term data rate, and this can be something like 100 Mb/s (megabytes per second).

How much fuel a car guzzles is equivalent to how much power a computer system uses. This is measured in watts, and because the numbers are so small we have to use scientific notation to document them. They include milliwatts, microwatts, and nanowatts.

The clock controls the frequency: how many instructions a computer can perform in a certain amount of time. These are measured in Hertz. The clock is the metronome of the computer: the faster the clock, the quicker it can process instructions. You may have heard of the phrase ‘overclocking’ – this is when users modify the clock speed so it runs faster than usual. However, if you overclock too much, this can exceed the limitations of the hardware, and cause glitches or even destroy the circuits.

Computer speed is of crucial importance to how well a computer performs, and there are many ways in which faster speeds can be achieved – we will look at this in a later post.

The Computer System Model

To represent a computer system we use block diagrams such as the one shown below. The von Neumann model is the most common – this is where a computer has five key components: a CPU, memory, a system bus, an input, and output. Without any of these, a computer would not be functional. Over the years, as technology has evolved, additional components have been added to the von Neumann model. These include peripherals, a cache memory, external memory devices, and additional buses.

Image sourced from: https://www.computerscience.gcse.guru/theory/von-neumann-architecture 

The Stanford architecture for example uses two different types of bus: one for instructions, and one for memory. This is to avoid what is famously known as the von Neumann bottleneck.

You can read more about the different types of computer architecture in this post.

Electronic Circuits

Computers process information by passing signals through electronic circuits. Various components are involved to make these highly complex circuits, but the fundamental component is the transistor.

The transistor was created in the 1950s, and replaced the vacuum tubes in early computers. The transistor can be used as a switch in a circuit, its state being either on or off, effectively representing a 1 or 0. These control the flow of data which of course is simply a series of 1s and 0s.

Transistors can be combined to make logic gates which make 1s and 0s depending on their input. These are used to perform mathematical operations, and are known as combinational circuits.

Logic gates, aside from being used to do arithmetic, can be used to control sequences. These are known as synchronous circuits which require the clock to synchronise the circuit: hence its name.

Flip-flops or data latches can be built from logic gates to create storage for binary data, where the signal loops through a circuit. This means the circuit retains the value, creating memory, for example the 8-bit register.

Speed Vs Complexity

So we now know what makes up ‘computer architecture’. But how do all these components relate to each other?

Electronic circuits use a lot of power and generate heat. Many technological innovations have been created to tackle the problem of making computers more energy efficient and reduce heat and time.

We can improve speed by increasing the speed of the clock – but even this isn’t simple. If a clock goes faster than its circuits can keep up with, the computer cannot function. Smaller circuits equal faster processing speeds, but also more heat. It is a delicate balancing act in designing faster and more powerful computers: this is how the CISC and RISC processor designs came about.

CISC stands for Complex Instruction Set Computer, but because the instructions were not used in an efficient way, RISC, or Reduced Instruction Set Computer, was introduced which meant the architecture used less instructions resulting in less complex circuits and higher clock speeds.

CISC completes tasks using mainly assembly code. This use of low-level language means processors have dedicated hardware to process instructions. For example, it will have a dedicated instruction such as MULT for multiplying two numbers together. This dedicated hardware means more circuitry, making it much more complex. The compiler doesn’t have to do as much work to translate the instruction into assembly code, but it does take the hardware longer to process, meaning it takes more time and energy. CISC architecture is usually found in larger devices such as desktop computers and laptops.

RISC aim to complete tasks within a single clock cycle. A complicated instruction for multiplying numbers together would not exist in a RISC architecture – instead, it uses the compiler to convert the instruction into assembly code. RISC uses less transistors and simpler hardware, resulting in less energy. It is much more efficient than RISC as a result of pipelining. RISC architecture is used in small devices such as phones, tablets, and other embedded systems.

This video describes the difference between CISC and RISC architectures:

Multicore processors also achieve better performance by having many CPUs on one chip. This is called parallel processing, where the the processors all work together to complete a task much more efficiently than serial processing, which is the processor working through each task sequentially.

References

C. Crispin-Bailey, From Architectures to Operating Systems, First Edition, UK: Independently published, 2019

Craig’n’Dave. 6. OCR A Level (H046-H446) SLR2 – 1.1 CISC vs RISC. (Aug. 19, 2020). Accessed: Aug. 12, 2025. [Online Video]. Available at: https://youtu.be/PaeXsm5HGJs?feature=shared

ComputerScience GCSE Guru. Von Neumann Architecture. ComputerScience.GCSE.Guru. [Online]. Available at: https://www.computerscience.gcse.guru/theory/von-neumann-architecture [Accessed: Aug. 08, 2025]