By Dr. Lindan A. Moya | 04/14/2025
Technology continues to drive advancements across all kinds of industries, but what are the fundamental components that make up computer systems? At the most basic level, a computer consists of a combination of hardware and software.
All computers have essential major components in common, including:
- The motherboard
- A central processing unit (CPU)
- Storage
- Memory
- An operating system
- A variety of software programs
- A power supply
Each computer has what's called a computer architecture, which is a set of instructions that define how the computer hardware and software components interact with one another. The computer architecture also sets rules for how the computer functions and how its CPU, input and output devices, and storage units work together.
Computer Hardware Components
The motherboard, central processing unit, graphics processing unit (GPU), and random access memory (RAM) are the main computer’s hardware components. In addition, computer hardware includes:
- A hard disk drive
- Audio components
- A monitor for viewing information
- A mouse for giving commands to the computer
An easy way to distinguish hardware components from software is that hardware is a physical component – something you can touch – whether it’s an internal or external component to the computer system.
By contrast, software is a set of code or instructions that enable the computer to perform a specific function. For example, Microsoft Excel® is an application used to create spreadsheets and graphs and to perform calculations.
The Motherboard
The motherboard is the main circuit board in a computer, sometimes referred to as the main printed circuit board (PCB). Think of it as the backbone of the computer.
The motherboard connects all the internal components of the computer, such as:
- The CPU
- The GPU
- The random access memory
- The read-only memory (ROM)
The motherboard provides power and allows all the other components of the computer device to communicate with each other.
Due to size constraints, laptops have specialized motherboards with hardware already soldered onto the board permanently. This type of manufacturing keeps laptops small and light, but it limits the ability to perform repairs or upgrades to the computer.
On desktop computers, motherboards and components can be upgraded. If a motherboard or one of its components fails, they can be replaced by a computer technician.
Central Processing Unit
The CPU is probably the next most important part of a computer’s hardware, serving as the main memory of the computer. It acts like the brain in a computer by executing instructions for the computer.
It consists of a processing unit that processes instructions, an arithmetic logic unit for executing instructions, and a register to store data and instructions. The CPU operates by fetching and decoding instructions that it receives from the computer’s memory and then performing those functions.
The faster the CPU is, the faster a computer can perform tasks. The processor speed (also called clock speed) is measured in gigahertz (GHz). For example, a processor with a clock speed of 2.0 GHz can process 2 billion cycles per second.
CPUs generate a lot of heat, which is why laptops and desktop computers have built-in fans. Due to their size, laptops are not able to cool the fastest processors.
If you need a computer with a high processing speed (for playing games or graphic design), a desktop computer with a fast central processing unit and a larger fan is the better choice for high system performance.
Graphics Processing Unit
The GPU handles graphical operations, such as images and animation. It is responsible for reproducing graphical representations and effects.
The fastest GPUs are used for gaming systems. The GPU is critical for all computers; if it fails, the computer is unable to communicate with the monitor and displays a blank screen.
Random Access Memory
Random access memory (RAM) is one of several types of memory devices used in a computer. It is used for temporary storage.
For instance, RAM stores information needed by programs currently running so it can be accessed quickly. RAM is faster than a hard disk drive (HDD) or a solid-state drive (SSD). When the computer is turned off, the RAM memory is erased.
Read-Only Memory
Read-only memory is a type of permanent memory that cannot be changed. ROM is critical since it stores permanent data and instructions for the desktop computer or laptop to boot up. Even after the computer is powered off, the ROM still retains the data necessary to start the computer up again.
Storage Devices
There are several types of storage devices used in computers. Typically, storage devices function as both input and output devices.
The two internal (built-in) storage devices are hard disk drives and solid-state drives. The information stored on these is permanent, even after a computer is off, unless the drive is severely damaged. (In fact, even after a file is deleted on an HDD, it can be recovered.)
Hard Disk Drives and Solid-State Drives
An HDD is literally a spinning, magnetic disk. This disk allows the computer to write information on it or for information to be read from it.
SSDs consist of flash memory, which includes a range of integrated circuits to store and retrieve data. Most new computers use SSDs. These devices do not have any moving parts, so they’re faster than HDDs and are less prone to failure.
HDDs and SSDs can also be peripheral computer hardware devices attached to a computer system. Often, these peripheral storage drives are used to archive information or move that information to another computer without using a network.
Moving the drive’s information to another computer in this manner is sometimes referred to as “sneakernet” since you are not using a network to move data from one location to another.
Peripheral Input/Output Devices
Peripherals are usually output or input devices; data is either flowing into the computer or out of the computer. These devices communicate with the computer system and are either hardwired or wireless.
They might use Universal Serial Bus (USB) cables, Ethernet cables, or High-Definition Multimedia Interface (HDMI) for wired connections. Apple computers have additional types of input device connectors, such as Thunderbolt. If the connection is wireless, then Bluetooth® or a wireless local network (WLAN) is the typical technology used.
Keyboards and Mice
Keyboards and mice are peripheral input devices. Laptops have compact, built-in keyboards and mice (usually touchpads), but users often attach an external, full-size keyboard and mouse for both comfort and functionality.
An external keyboard or mouse can be wireless or may connect to a computer via a cable and a USB port. A separate keyboard and mouse are always necessary for a desktop computer.
Monitors
External monitors are output devices that are essential for desktop computers, with the exception of all-in-one desktop units. Laptops have built-in monitors, but users often connect large external monitors to laptops for comfort and functionality.
All-in-one computers (AiO) are compact desktop computers that have the CPU, memory, and other components built into the monitor. This configuration is like a laptop in that users are not likely to be opening the case to exchange boards or upgrade storage. AiO computer devices, however, still require an external keyboard and mouse.
Printers and Scanners
Printers are output devices, while scanners are input devices. Today, most computers use wireless laser printers, many of which can perform other functions, such as scanning documents directly from the device.
Most commercial quality printers have built-in HDD or SDD to store a document on the hard disk of the printer. Some printers allow secure printing to prevent unauthorized user access to printed documents. When a file is sent to the printer, it can be held in memory and not printed until the authorized recipient logs into the device.
Home office printers do not have an internal HDD or SDD, but they often have memory card slots for SD cards or USB ports for flash drives. Users can print files from the SD or flash drives without a computer being connected to the printer.
Other Input Devices
Joysticks, cameras, speakers, and microphones are all other types of input/output devices that can be connected to a computer system. Most laptop computer systems now include built-in cameras, microphones, and speakers.
Many monitors are also now touch-screen capable, allowing the screen to be used as both an output and input device. A pen or stylus can also be used to draw or write on a touchscreen monitor.
Wi-Fi Networks
Most homes that have internet services use a wireless router to provide connections to TVs, computers, printers, and smart home devices like thermostats or security alarm systems. A Wi-Fi network commonly has several components, including:
- A modem that connects to the internet
- A switch to connect extra computers to the router
- A router that connects the devices to the modem
- A wireless access point to broadcast Wi-Fi signals (sometimes built into the router)
Software Components of a Computer
Sophisticated software in a computer degice provides instructions to tell the computer hardware what to do. The software is written in computer-understandable languages and typically falls into three categories:
- Operating system (OS) software
- Application software
- Security software
Operating System Software
Operating system software controls the computer's processes, software, and hardware. It allows users with little experience to more easily operate a computer.
The two more popular operating systems for personal computers are:
- Microsoft® Windows – used in many PCs
- MacOS – used for Apple® computer products
Application Software
Spreadsheet, word processing, e-mail, and database software are among the more well-known software programs used on personal computers to complete tasks and to store data. However, many other applications are available for computer users. For instance, there is software for photograph and video editing, image creation, and project management.
Security Software
Computer operating systems such as Windows and MacOS have built-in antivirus software to protect a computer from malware. However, many users opt to install a third-party antivirus software for extra security and additional features such as protection against spam.
Computer Technology and Computer Science Degrees at American Public University
For adult learners who are interested in topics such as programming and computer science, American Public University offers several degrees:
- An online Associate of Arts in Computer Technology
- An online Bachelor of Arts in Computer Science
- An online Bachelor of Science in Computer Science
These programs feature a variety of courses to suit a student’s professional interests, including an introduction to computer science, advanced productivity applications, and the fundamentals of programming. Other courses included an introduction to programming, machine architecture and organization, algorithms and data structures, and network security fundamentals.
For more information, visit APU’s information technology degree program page.
Bluetooth is a registered trademark of Bluetooth SIG, Inc.
Microsoft is a registered trademark of the Microsoft Corporation.
MacOS is a registered trademark of Apple, Inc.