The computer case or system unit is the component that holds all of the computer parts, it is the cabinet that contains the computer's power supply, motherboard, memory, disk drives and other peripheral control units; and is usually designed in such a manner to make fitting a motherboard, wiring, and drives as easy as possible to keep it tidy and presentable.
Cases come in all different sizes and shapes to accommodate various types of computer components and to satisfy the consumer’s needs. Tower case is a vertical computer cabinet which is a common design for servers and high-performance workstations; tower cases have more room for storage and card expansion than horizontal desktop cases and all-in-ones, which are a desktop computers that house every component except the keyboard and mouse inside the same case as the monitor. The all-in-one's primary advantage is saving space on the desk. Its disadvantages are twofold: if any component fails other than the keyboard or mouse, the entire unit must be brought into the shop for repair. Secondly, there is generally no internal expansion for storage; however, external drives can always be added.
Computer cases rely on computer fans inside them to create proper airflow to keep all the internals cool and working reliably. Computer case sizes are known as form factor, which are:
· Very small form factor: Supports Mini ITX motherboards (SFF)
· Small form factor: Supports micro ATX motherboards (Mini Tower)
· Standard form factor: Supports standard ATX motherboards (Mid Tower)
· Larger form factors: Supports ATX and XL-ATX motherboards (Full Tower)
So, unlike motherboard form factors, mentioned above, there aren't standardized specifications for computer cases. That said, these computer case sizes (SFF, Mini Tower, Mid Tower, Full Tower) will apply to the vast majority of PC casings.

The motherboard is the main board that is screwed directly inside the computer case. All other cards and components (CPU, RAM, drives, power supply) plug directly into the motherboard. Its function involves integrating all the physical components to communicate and operate together. It is the primary printed circuit board in a computer or other electronic device. In a modern desktop computer, the motherboard contains CPU and RAM sockets and the chipset, which houses the control circuits for all primary peripheral devices (drives, keyboard, mouse, etc.). A motherboard also has PCI-Express slots for a high-end graphics card or other peripherals; a good motherboard offers a wide amount of connectivity options. Every motherboard contains a specific chipset and a slot for one type of CPU chip, and these change periodically as does everything. While PCI Express (PCIe) has been the dominant bus for more than a decade, now there is the M.2 interface. New motherboards may have one or two M.2 slots along with several PCIe slots. Motherboards come in various sizes:
· Pico-ITX
· Nano-ITX
· Mini-ITX
· Micro-ATX
· Standard-ATX
· XL-ATX
Motherboards can be found in virtually all computers, especially desktop and laptop PCs. The components that connect through them include chipsets, central processing units (CPU) and memory. The external peripherals include Wi-Fi, Ethernet and graphics cards with the graphics processing unit, or GPU. The type of motherboard installed in a PC has a great effect on a computer's system speed and expansion capabilities.

The CPU or central processing unit, also called "processor" is basically like the brain of computer systems. It processes all the information on a computational level. The CPU is made up of the control unit, which executes the instructions, and the ALU, which performs the calculations and logical operations. Inside a CPU there are thousands of microscopic transistors, which are tiny switches that control the flow of electricity through the integrated circuits.
The central processing unit is usually seated in a socket that utilizes a lever or a latch with a hinged plate with a cut-out in the center to secure the CPU onto the motherboard. It has many copper pads underneath it for the socket contacts to push up against them to make electrical contact.
Some common examples that the CPUs can be attached to the motherboard are:
· ZIF (Zero Insertion Force)
· PGA (Pin Grid Array)
· LGA (Land Grid Array)
· BGA (Ball Grid Array)
A clock speed refers to how many instructions a CPU can manage in a second and generally indicates how fast it is. The multi-core processor revolution began with dual-cores and quad-cores. Instead of focusing on advancing clock speed, manufacturers fitted multiple CPUs on one chip. Hyper-threading allows a single processor core to perform like two by dividing workloads for simultaneous processing. A processor, also dissipates energy in the form of heat due to the resistance in the electronic circuits, especially when it is working under high loads. It will run even hotter when it is set to a higher clock speed to make it run faster; which is called overclocking. This is why a heatsink and fan assembly are required to draw the heat away from the central processing unit and distribute it to thin sheets or fins of metal for the fan to cool down.

RAM (Random Access Memory) is the hardware in a computing device where the operating system (OS), application programs and data in current use are kept so they can be quickly reached by the device's processor. RAM is the main memory in a computer. It is much faster to read from and write to than other kinds of storage, such as a hard disk drive (HDD), solid-state drive (SSD) or optical drive. RAM is volatile memory, meaning it loses all the stored data when power is lost. When the computer is rebooted, the OS and other files are reloaded into RAM, usually from an HDD or SSD.
If RAM fills up, the computer's processor must repeatedly go to the hard disk to overlay the old data in RAM with new data. This process slows the computer's operation. A computer's hard disk can become completely full of data and unable to take any more, but RAM won't run out of memory. However, the combination of RAM and storage memory can be completely used up.
The term random access as applied to RAM comes from the fact that any storage location, also known as any memory address, can be accessed directly. RAM is organized and controlled in a way that enables data to be stored and retrieved directly to and from specific locations. RAM is similar in concept to a set of boxes in which each box can hold a 0 or a 1. Each box has a unique address that is found by counting across the columns and down the rows. A set of RAM boxes is called an array, and each box is known as a cell. To find a specific cell, the RAM controller sends the column and row address down a thin electrical line etched into the chip. Each row and column in a RAM array has its own address line. Any data that's read flows back on a separate data line.
Having more RAM in a computer cuts down on the number of times the processor must read data from the hard disk, an operation that takes longer than reading data from RAM. RAM access time is in nanoseconds, while storage memory access time is in milliseconds.
Two main types of RAM are: Static RAM and Dynamic RAM.
Each DRAM cell has a charge or lack of charge held in an electrical capacitor. This data must be constantly refreshed with an electronic charge every few milliseconds to compensate for leaks from the capacitor. A transistor serves as a gate, determining whether a capacitor's value can be read or written. Dynamic RAM is a standard computer memory of the many modern desktop computers. In SRAM, instead of a capacitor holding the charge, the transistor acts as a switch, with one position serving as 1 and the other position as 0. Static RAM requires several transistors to retain one bit of data compared to dynamic RAM which needs only one transistor per bit. As a result, SRAM chips are much larger and more expensive than an equivalent amount of DRAM.

Graphics Card or Graphics Processing Unit (GPU) is an output device that processes the data from the motherboard and sends the appropriate information to the computer’s screen. Monitors can be connected to it using HDMI, DisplayPort, DVI, or VGA connectors.
It can also be referred to as a video or display card; video card takes the burden of all the video processing from the main CPU. A video card plugs into a PCI Express (Peripheral Component Interconnect Express) slot on the motherboard. It is a serial expansion bus slot capable of high bandwidth in two directions. A graphics card has a GPU (Graphics Processing Unit), and it is slower than a CPU but is designed to deal with mathematical operations required for video rendering. Because of the large processing requirements for a gaming GPU, fans are almost a given. Video cards use GDDR (Graphics Double Data Rate) SDRAM, which is specially designed to optimize graphics performance.
A GPU provides the fastest graphics processing, and for gamers, the GPU is a stand-alone card plugged into the PCI Express (PCIe) bus. GPU circuitry can also be part of the motherboard chipset or on the CPU chip itself. A GPU performs parallel operations on multiple sets of data. Although it is used for 2D data as well as for zooming and panning the screen, a GPU is essential for smooth decoding and rendering of 3D animations and video. The more sophisticated the GPU, the higher the resolution and the faster and smoother the motion. GPUs on stand-alone cards include their own memory, while GPUs built into the chipset or CPU chip share main memory with the CPU.

They are widely used for scientific and AI applications, as well, such as voice and image recognition, big data analysis, self-driving cars, medical diagnosis and other automation technologies.

HDDs are traditional storage devices with spinning platters that read and write data. SSDs use newer technology to store data on instantly-accessible memory chips. SSDs are faster, quieter, smaller, more durable, and consume less energy, while HDDs are cheaper and offer more storage capacity and easier data recovery if damaged. SSDs and HDDs are both storage devices, but the way they work is quite different. The main difference between a solid state drive (SSD) and a hard disk drive (HDD) is how data is stored and accessed. HDDs use mechanical spinning disks and a moving read/write head to access data, while SSDs use memory chips.
Solid state drives (SSDs) are newer types of disks that store information on flash memory, which consists of individual memory cells storing bits that are instantly accessible by the controller. SSD speeds vastly outpace those of HDDs, and the rapid data transfer will improve computer’s performance drastically. SSDs improve the speed at which large amounts of data are loaded at once. The following processes work faster with an SSD:
· Booting up operating system
· Starting a program
· Loading a new video game level
· Opening a huge file in a resource-intensive program
· Importing and exporting video files
· Previewing video files in editing software
An HDD enclosure contains a series of platters covered by a ferromagnetic coating. The direction of the magnetization represents the individual bits. Data is written and read by a fast-moving head, similar to the way vinyl record albums work. The disk spins at 7200 RPMs so data can be read very quickly.
Since all of these pieces are mechanical, the hard disk is the slowest and most fragile component of any computer. But HDDs can be extremely cost efficient for long-term offline storage, as most of the benefits of an SSD over HDD are only related to day-to-day usage.
SSD storage comes in several shapes and sizes. Initially, SSDs were made to mimic the size and shape of the most common HDDs to make upgrading as easy as possible. Now we can find SSDs in much smaller form factors, like M.2 SSD SATA or M.2 SSD PCIe NVMe, mSATA and 2.5" SSD.

Power supply or PSU (power supply unit) is a hardware component of a computer that supplies all other components with power. The power supply converts a 110-115 or 220-230 volt AC (alternating current) into a steady low-voltage DC (direct current) usable by the computer and rated by the number of watts it generates. It contains capacitors capable of holding a strong electrical charge, even if the computer is off and unplugged for an extended period.
The power supply is located at the back of the computer, usually at the top. However, many more recent tower computer cases house the power supply at the bottom back of the case. In a desktop computer case (all-in-one), the power supply is located at the back left or back right.
This is a list of parts inside a power supply:
· A transformer that controls the incoming voltage by stepping it up or down
· A rectifier that converts AC (alternating current) into DC
· A filter that smooths out the DC (direct current) coming from a rectifier
· A voltage regulator that controls the DC output, allowing the correct amount of power, volts or watts, to be supplied to the computer hardware
Everything contained in the computer chassis is powered by the power supply. For example, the motherboard, RAM (random-access memory), CPU (central processing unit), hard drive, disc drives, and most video cards are all drawing power from the power supply. Any other external devices and peripherals, such as the computer monitor and printer, have a power source or draw power over the data cable like some USB (universal serial bus) devices. If the computer is a laptop or an All-in-One computer, the display is powered by the computer power supply.

A sound card is a computer component responsible for generating and recording audio. It enables users to connect analog speakers, headphones and microphones to their computer. Most modern computers have a built-in sound card in the motherboard. The sound card's primary function is to convert digital signals into analog output for speakers and headphones. It also converts signals from microphones to digital input.
A sound card operates through a digital-analog-converter (DAC) and an analog-digital-converter (ADC) and uses dedicated chips to lessen the CPU load. A preamplifier boosts signal levels and controls volume. It may also be able to perform audio processing, such as audio equalization.
At the very least, a sound card provides a 3.5 mm stereo audio out and audio in TRS (tip, ring, sleeve) jack. However, many modern devices now use a single 3.5 mm TRRS (tip, ring, ring, sleeve) jack that combines both the headphone and microphone into a single port. Advanced sound cards offer additional input and output jacks. These may have additional 3.5 mm jacks for 5.1 or 7.1 channel surround sound, digital outputs or a digital optical audio port.
As technology continues to evolve, computers increasingly provide digital audio output. In such cases, HDMI and Bluetooth connections are digital-only and do not require a sound card. Instead, an external device such as a TV or Bluetooth headphones perform digital-to-analog conversion.
However, basic sound cards will still be included in most computers because analog speakers and headphones remain widespread.

An expansion card is a PCB (printed circuit board) that plugs into an expansion slot on a computer motherboard. An expansion card, or add-on card, is used to provide additional functionality to the system or to upgrade an existing function, such as sound or video. For example, an expansion card is a sound card, network card, or dedicated GPU. The most popular expansion slot standard is PCI Express (PCI-e).
An expansion slot is a connection or port inside a computer on the motherboard or riser card. It provides an installation point for a hardware expansion card to be connected.

There are various types of expansion cards available, depending on the purpose and functionality one requires. Some common examples include graphics cards, sound cards, network interface cards (NICs), WiFi cards, universal serial bus (USB) expansion cards, and storage controller cards such as redundant array of independent disks (RAID) cards. We can install multiple expansion cards in our computer if we have enough available expansion slots on the motherboard. Most motherboards offer several slots to accommodate various types of expansion cards. However, we should keep in mind that adding too many cards may consume additional power and generate more heat, so we need to ensure our power supply and cooling system can handle the extra load.

Unlike desktop computers, laptops have a more compact form factor and limited expansion capabilities. While some laptops may have a few specific expansion options, such as upgrading the memory or replacing the hard drive, they generally don't support traditional expansion cards like desktop computers do. However, there are external expansion options available, such as universal serial bus (USB) - based devices or docking stations, which can provide additional connectivity and functionality for laptops.

A monitor is an electronic output device used to display information being entered and processed on a computer. The primary use of a monitor is to display images, text, video, and graphics information generated by the computer via a computer’s video card. It can be referred to as the main output device of a computer device.

1. CRT (Cathode Ray Tube) Monitor:
It is a technology used in early monitors. Today's Flat Panel Monitors i.e. LCD and LED display monitors have replaced the CRT monitors.
2. Flat Panel Monitor:
These types of monitors consist of a flat display panel. These monitors are portable and take up less room. They use less energy than CRT monitors do. Due to the fact that they do not emit hazardous radiation, these monitors are more efficient.
3. LED Monitor:
It is a flat-screen computer monitor, also referred to as an LED display. It is very slim and shallow in size along with being very lightweight. It makes use of a panel of LEDs as its light source.

Monitors require one of the following kinds of connectors or components to connect with a computer:
1. VGA (Video Graphics Adapter)
It is used to connect a computer with a monitor, projector, etc. It can only show lower quality, and lower resolutions displayed on the screens.
2. Thunderbolt
It connects peripheral devices to a computer, including a mouse, keyboard, printer, scanner, and more. It has the ability to transmit data over great distances and transport DC power.
3. HDMI Cable
High Definition Multimedia Interface is the full form of HDMI. It has the capacity to transfer high-bandwidth, high-quality audio and video streams between gadgets. It can be utilised with a DVD player, HDTV, Blu-ray player, or projector.

A keyboard is an input device used to enter characters and functions into the computer system by pressing buttons, or keys. It is the primary device used to enter text. A keyboard typically contains keys for individual letters, numbers and special characters, as well as keys for specific functions. A keyboard is connected to a computer system using a cable or a wireless connection.
Most keyboards have a very similar layout. The individual keys for letters, numbers and special characters are collectively called the character keys. The layout of these keys is derived from the original layout of keys on a typewriter. The most widely used layout in the English language is called QWERTY, named after the sequence of the first six letters from the top left.
Most keyboards also include a set of function keys at the top (F1, F2, etc.) and a separate numeric keypad to the right.
For many tasks, we need to press more than one key at the same time. For example, to get a capital letter 'A' we need to press the Shift key and the A key at the same time. When reading or writing instructions for how to accomplish a particular task, this would be described as 'Shift + A'. As another example, in most software applications, Ctrl + S means to save the current document. Ctrl + Alt + Del, also referred to as Control-Alt-Delete; in older computer systems, this actually rebooted computer; in more modern versions of the Windows operating system, the combination brings up options to log off or shut down, as well as options to force a particular software application to quit.

Touch typing is a method of typing without the use of the sense of sight, or simply by feeling the keyboard. However, the sense of touch is only slightly involved since this typing method is governed by muscle memory through rigorous training with the proper typing method.
Touch typing is done using a standard QWERTY keyboard with the hands placed at a starting location, called the "home row keys." The home row keys for the left hand are the "ASDF" keys, and are "JKL;" for the right hand. Each finger of each hand has dedicated keys assigned to it which it can easily reach. The design of the QWERTY keyboard, for the English language, ensures that letters that are commonly pressed or used in succession are as far away as possible to promote speed and the use of both hands, thereby distributing strain to all fingers rather than just a few. Though the standard QWERTY keyboard is said to have room for improvement in terms of speed and ease of typing, it is said that this change has been resisted by touch typists everywhere because of familiarity.

A computer mouse is a handheld hardware input device that controls a cursor in a GUI (graphical user interface) for pointing, moving and selecting text, icons, files, and folders on computer. In addition to these functions, a mouse can also be used to drag-and-drop objects and give an access to the right-click menu.
A mouse has at least two buttons, called the left mouse button and the right mouse button. Most models of mouse also include a scroll wheel which allows us to easily scroll web pages. Some include extra buttons, or may eliminate the scroll wheel and use a touch-sensitive panel on the top instead.
A wired mouse has a cable coming from it that can be plugged into the computer, via a USB port which is found on the computer case. Some models of computer mouse can also connect to the computer wirelessly using Bluetooth.
Once our mouse is connected, we’ll see an arrow on the screen which is known as the mouse pointer. It is also sometimes called a cursor. If we move or hover the pointer over an element that can be clicked, it may change from an arrow into a hand, indicating that we can click it. The right-click action is performed by clicking once on the right mouse button. Depending on what we click, a right click usually makes a menu appear that has a range of options in it. A double-click is performed when we click twice with the left mouse button. The two clicks need to be done in rapid succession, and we might find it can take a bit of practice to get this just right. The main purpose of the double-click is to open files such as photos or documents.
We can scroll a web page or a multi-paged document using the scroll wheel on the mouse. When we rotate the wheel with our index finger while on a web page, we make the contents of the page move up or down. We can then see content on the parts of the page that don’t fit on the screen.

Adapters are hardware or software components that enable different devices or systems to communicate with each other. They act as translators, converting signals and facilitating communication between devices that use different connectors, protocols, or interfaces. Here are some common types of adapters:
1. Network Adapters: Also known as Network Interface Cards (NICs), these allow computers to connect to a network, enabling data exchange and communication.
2. Display Adapters: These transmit video signals from a computer to a display device like a monitor or projector.
3. USB Adapters: These connect USB devices such as printers, keyboards, and mice to a computer.
4. Host Bus Adapters (HBAs): These connect storage devices like hard drives to a computer's motherboard.

Controllers are devices or software that manage the operation of other devices. They act as the brain, directing the flow of data and ensuring that devices work together smoothly. Here are some examples:
1. Disk Controllers: These manage the read and write operations of hard drives and SSDs.
2. Network Controllers: These handle data transmission and reception over a network, often integrated into network adapters.
3. Game Controllers: These include devices like gamepads and joysticks that allow users to interact with video games.

In a computer system, adapters and controllers often work together to ensure seamless operation. For example, a network adapter (hardware) might include a network controller (software) that manages data packets and communication protocols.