In this section, we cover the major hardware components of a microcomputer system responsible for input, output, processing, storage, power supply, and communication. At Computer Repair MIA, we understand that most input and output devices are located outside the computer case, while the primary processing and storage components reside inside.

The most critical component housed within the case is the central processing unit (CPU)—also known as the processor or microprocessor. As the name suggests, the CPU is central to all computing processes. It reads data received from input devices, performs calculations and data processing, and sends results to output devices. The CPU also reads from and writes data to storage devices, executing instructions and managing tasks essential to system operation.

Regardless of whether a device is located inside or outside the case—and no matter its function—each hardware component requires one essential capability: a means of communication with the CPU.

To function properly, a device must be able to send data to and/or receive data from the CPU. The CPU may also need to control the device by sending it instructions, or the device may need to request service from the CPU.

Software is essential for device control. Without software, hardware is essentially useless. The software must know how to communicate with the device at a very specific level, and the CPU must be able to access this software to interact with the device. Each device responds to a unique set of instructions tailored to its specific functions. Therefore, the controlling software must include commands for every possible action the device is expected to perform.

Power is also required. All electronic devices need electricity to operate. Power can be supplied by the computer’s internal power supply or through an external power cable connected to an outlet.

In the following pages, we’ll take a guided tour of computer hardware—starting with components outside the computer case, then moving inward.

To keep things accessible, we’ve minimized technical jargon in this section. In later chapters, each component will be explored in greater depth.

External Components: Input and Output Devices

Most input and output (I/O) devices are located outside the computer case. These devices connect to internal components either wirelessly or via physical cables attached at ports. Ports are typically located on the back of the case, though some systems include front-facing ports for convenience.

Popular input devices include the keyboard and mouse.
Common output devices include monitors and printers.

The keyboard is the primary input device. Modern keyboards, known as enhanced keyboards, typically include 104 keys. Some are ergonomic, designed with a curved layout for greater comfort. In some models, a mouse can be connected directly to the keyboard, although it’s more common for the mouse to plug into a dedicated port on the computer case.

Keyboards receive electrical power from within the computer via the keyboard cable.

The mouse is a pointing device that controls the on-screen pointer. It uses either a rotating ball or an optical sensor to detect movement. Mice usually have one to three buttons on top, with different functions depending on the software. For example, in Windows Vista, the left button executes commands, while the right button opens a context menu of options.

Internal Components: Processing and Storage

At Computer Repair MIA, we know that most data processing and storage takes place inside the computer case. Before diving into those components, let’s explore what you’ll typically see when opening a case.

Common internal components include:

• A motherboard, which houses the CPU, memory, and essential circuits

• A hard drive and possibly a CD/DVD drive, used for long-term storage

• A power supply, distributing electricity to all internal components

• Adapter (expansion) cards, which help the CPU communicate with internal and external devices

• Cables, both for data and power

One of the first things you’ll notice inside a case are the adapter cards. These circuit boards hold microchips (integrated circuits or ICs) and their supporting circuitry. Adapter cards—also called expansion cards—are installed in long, narrow slots on the motherboard. They are built with microchips, most of which use CMOS (complementary metal-oxide semiconductor) technology.

You’ll also see small box-like components, including the power supply, hard drive, CD/DVD drive, and possibly a legacy floppy drive.

Inside the case, you’ll find two types of cables:

• Data cables – used to connect devices like hard drives or optical drives to the motherboard or adapter cards

• Power cables – used to deliver electrical power from the power supply to devices

A good rule of thumb: if the cable is flat and ribbon-like, it’s most likely a data cable.