To start with, let’s look at what a computer is. Simply put, a computer – also called a computing or computer system – is an electronic device that receives data input such as numbers, text, or images and uses a set of instructions (a program) to process and transform it into meaningful information under different formats as output.
The elements that make a computer system work are broadly categorised into two groups, hardware and software.
Hardware refers to the physical elements of a computer or electronic system: the machinery of the computer itself or external computer equipment. The keyboard, the monitor, and the electronic parts inside the central unit are all hardware.
By contrast, software represents the “non-physical” component, the instructions that tell a computer what to do. It allows us to “speak” to the computer without knowing the computer language. The most important blocks that form the software of a computer are the operating system (OS) and the applications.
The operating system acts as an interface between hardware and application programs. Since there are usually several different computer programs running at the same time, and they all need to access your computer's resources, the operating system coordinates it to make sure each program gets what it needs.
Application programs perform specific tasks on a system: a text editing program, a music player, a web browser and so on.
Hardware and software are strongly interconnected: without software, the hardware of a computer would have no function. Without the hardware needed to perform the tasks instructed by the software, the software would be useless.
Hardware components must have certain characteristics to allow the software to function well. These components of a computer system interact with each other to perform specific tasks so to understand them it is important to understand the entire process as they depend on each other to function correctly. Typically, this interconnection is represented in layers.
The highest layer of the computer system is the software applications – the programs we typically use that enable us to interact with the computer.
Below this layer we find the operating system – this acts as a translator between applications and hardware so they understand each other.
At the lowest layer we find the hardware – all the devices that we can physically touch. Operating systems must be hosted in specific hardware to function well.
This process is common to all computer systems, be it personal computers or industrial ones.
A closer look at hardware
We will now look at the main hardware components of a computer and what role each component plays. It’s important for us to know about these components and their characteristics because they determine how well computers perform the tasks we ask of them. When buying a new computer or replacing parts of the computer you have, you may need to know the specifics of the hardware to make sure it will work correctly for what you need: work, browsing the internet or playing games.
Although we will focus mainly on the personal computer – since it’s one of the most common types of computers – and the peripheral devices that are commonly used with it, the same principles apply to all computers.
The components of a general-purpose computer can be divided into two categories: internal and external. Internal computer hardware refers to those components designed to fit inside the computer system, which all carry out important roles. External components connect to a computer system from the outside. They are not necessary for the system to function, but they do make our experience easier or better in some other way.
The components of a computer include the following:
The processor or central processing unit (CPU) executes instructions organised in programs ("software") which tell the computer which data to process and how to process it. Without a CPU, we could not run programs on a computer.
It is often referred to as the “brain” of a computer, containing all the circuitry needed to process input, store data, and output results.
The speed at which the processor processes information is measured in gigahertz (GHz). Generally, the faster the speed, the faster the performance of the computer.
The memory unit is what allows the computer to remember data and information. Similar to human memory, there is short-term memory (RAM) and long-term memory (the hard disk drive).
RAM (random-access memory) and ROM (read-only-memory) are used to store computer data and this can be directly accessed by the CPU.
RAM is used to temporarily store information that is currently in use by the computer.
ROM is used to permanently store instructions that tell the computer how to start up. It also loads the operating system.
The hard disk drive (which can be either internal or external) is used to permanently store data and programs for as long as we need.
RAM’s content is volatile and deleted as soon as the computer loses power. To save your work even after the computer is turned off, you must save it onto permanent storage (an internal or external device).
Also known as the "main board”, it is the central circuit hub that allows connection between all components and peripherals attached to the computer.
The motherboard allocates power where it’s needed and communicates with and coordinates all other components – making it one of the most important pieces of hardware in a computer.
All other components plug into the motherboard either directly (straight into the circuit board) or indirectly (via USB ports) and work together to form the computer system.
The graphics or video card is a hardware device that plugs into the motherboard and enables the computer to display images on the monitor.
A graphics card's processor, called a graphics processing unit (GPU), is similar to a computer's CPU, but is specifically designed for performing the complex mathematical and geometric calculations that are necessary for graphics rendering.
GPUs are specialised processing cores that can be used to speed computational processes. Initially designed to process images and visual data, GPUs are now being adopted to enhance other computational processes, such as deep learning or modern artificial intelligence infrastructure.
Sound cards are internal hardware devices that plug into the motherboard and allow the computer system to produce sound. They also allow users to connect microphones in order to input sounds into the computer.
Power supply unit
A power supply unit is the point where power enters your computer system from an external power source and is then allocated by the motherboard to individual hardware components.
These are the devices through which data and instructions enter a computer.
Input devices fall into two categories: manual input devices (for example a mouse, keyboard, touchscreen, or scanner), which need to be operated by a human to input information, and automatic input devices (a barcode reader or card reader, for example) that can input information on their own.
When the inputted data has been processed it becomes usable information that is transmitted to the user through output devices.
An output device is a display screen, a printer, or another device that lets you see what the computer has accomplished.
In a laptop computer, all hardware components are integrated together. And to go even further, a smartphone contains the same elements integrated in an even smaller device.
When picturing a computer, most people imagine the personal computer that they have at home or their desktop computer at work. However, computers today come in many forms and are used for a large variety of functions. From processing and producing data, computers can also have “acting” capacities like controlling systems, robotics and so on.
The revolution of data storage devices
A digital computer represents data using the binary numeral system. That means that any form of information, be it numbers, text, pictures or audio can be converted into binary digits, each of which has a value of 1 or 0. The most common unit of storage is the byte, equal to 8 bits. A piece of information can be handled by any computer or device whose storage space is large enough to accommodate the binary representation of the piece of information, or simply data.
Therefore, the capacity of storing data provides computers with one of their fundamental function, that of retaining digital data. While we take this function for granted today, computer data storage has come a long way from the early days of computing.
At the beginning computers were programmed using stiff sheets of paper with commands and other data represented by the presence or absence of holes. These cards would later be replaced by reels of magnetic tape, which were easier to manage space-wise, since storing stacks of cards was very impractical, but it still took a lot of time and work to program and the process was tedious.
The first personal computers had no internal data storage (hard drive), so software, which was at that point very simple and only required small amounts of data, was loaded via floppy disks. This changed with the evolution of hardware. When hard drives became standard, software could be installed on the computer. This meant that companies could sell computers with an operating system and applications already installed. People no longer needed to change disks to switch between different pieces of software, making computer work more efficient and effective.
Things continued to improve: we got CD-ROMs, then CDs, then DVDs, and increasingly larger hard drives. And with the evolution of the internet, people don’t need to buy software on CDs anymore as we can download our programs, or even use them directly from the cloud.
The types of computers
We are now going to look at different computer types currently available, according to their general purpose.
The personal computer (PC) is a computer designed for general use by a single person. It has a connected monitor, keyboard and CPU, and has developed into a convenient and flexible tool capable of operating independently or as part of an organisational network. Today, personal computers come in many forms and sizes, from desktops to laptops and from mobile phones to tablets. We will look more closely at the types of PC in the next section.
Servers are computers that have been optimised to provide services to other computers over a network, and they usually have powerful processors, lots of memory and large hard drives. There are, for example, home media servers, web servers, and print servers. There are also file servers and database servers. Companies rely on servers to provide information, process orders, track shipping data, crunch scientific formulas, and so on.
These are large computers with high capacity and processing speed. Mainframes execute many programs at the same time and are capable of supporting hundreds, or even thousands, of users simultaneously. Mainframes have very resistant architectures, resulting in high reliability and security. These machines are defined by high availability, often run for years without interruption, with repairs and hardware upgrades taking place during normal operation, and even being able to continue running in case of a component failure.
They are therefore mostly used by governments and large organisations for bulk data processing, critical applications, and to help to secure countless sensitive transactions, industry and consumer statistics, among other tasks.
Supercomputers are like the race cars of the computer world; they are at the forefront of current processing capacity, particularly in terms of speed of calculation. They can be built either from a small number of very powerful components, or from a larger set of less powerful units and are used for specialised applications that require an immense number of mathematical calculations. Supercomputers are found, for example, at scientific institutes or weather forecasting stations, where calculation speed is essential.
Embedded computers are incorporated into other devices, rather than being stand-alone computers, and are designed to perform specific tasks. Examples include digital cameras, music players, and almost any kind of industrial or domestic control system. For example, most modern mobile phones actually contain quite a few separate computers: alongside the SIM card, a phone might have another microprocessor to handle the radio communications and a second computer chip to run all the processor-hungry applications like games. Even washing machines now have a microprocessor inside them, to calculate the washing cycle and drive the clothes drum motor as efficiently as possible.
As we have seen, today’s computers are very versatile and their flexibility and enhancement potential speak to the idea that the computer revolution is still continuing.