# Introduction to Information Technology/Computing Hardware
## Introduction

Computer hardware consists of the physical components within a computing device that work together to form a system, enabling the computer to process data. Computer hardware can be internal or external. Internal components are the parts not visible without opening the device, while external components are components on or attached to the outside of the device. Examples of internal devices are storage, processing, and fans. Examples of external devices are keyboards, monitors, a mouse, and anything connected directly to the device (like a USB or printer).

## Major Components of a Computing Device
### Central Processing Unit (CPU)

The central processing unit (CPU) is the brain of any computer system. It is a component designed to handle I/O (the exchange of data between the computer and the user) and basic control of computer systems. More specifically, the CPU manages the basic arithmetic, logical, and I/O operations of a computer system. The CPU takes instructions from a program, decodes the instructions, then executes the instructions. This process is called an instruction cycle. The average modern microprocessor completes hundreds of thousands of these instructions cycles every second.
The CPU comes equipped with many specific components. The first component is known as the arithmetic logic unit (ALU), which performs simple arithmetic and logical operations. The second component is the control unit (CU), which directs all of the processor's operations for the various components of the computer. The CU reads and interprets instructions from memory and converts them into multiple signals to activate other parts of the computer, following those instructions. The CU calls upon the ALU at times to perform the necessary calculations.
The CPU also generates large amounts of heat. This requires a heatsink and fan attached to the CPU with thermal grease (also called thermal paste) to maintain safe temperatures.The thermal grease creates a uniform contact surface for excess heat to transfer across. Some computer builders prefer to use a larger aftermarket cooler or liquid cooler to keep the CPU protected from high temperatures.

### Power Supply Unit

Power Supply Unit (PSU) is a vital hardware component of a computer; without a power supply a computer would not work. The power supply converts alternating current (AC) line from an electrical outlet to a lower voltage direct current (DC) power needed to run a computer. The power supply unit handles supplying power to the various electrical components of the computer. There are two kinds of power supplies, linear power supply and switch mode power supply.

### Motherboard

The motherboard is the main circuit board of the computer. It contains a socket for the CPU, memory slots for RAM, the BIOS, the controller ports for peripheral devices (keyboard, mouse, speakers, etc.), and even expansion slots for a video card or sound card. The motherboard also facilitates communication between all the computer's devices and systems. It is usually the main component of the computer and is often referred to as a system board. Some motherboards contain extra connectors that allow expansions to upgrade the computer and add additional chips.
Motherboards usually have one or more expansion slots. These slots are most commonly a PCI (Peripheral Component Interconnect) slot, or a PCI-Express 16x slot. These slots are most commonly used to connect devices such as a video card, sound card, WLAN adapter, etc. they are normally aligned with a expansion card cutout on the computer case to allow for cables to be plugged into them. Most ATX motherboards will have two or three PCI-E 16x slots depending on the brand and how high-end the board is.

### System Memory

System Memory -- also referred to as Random access memory (RAM) -- is a form of temporary storage that computers use to quickly access data. RAM is necessary due to inadequately slow hard disk drive (HDD) read and write speeds that are required for a computer's normal operation. The reason RAM is random is because it gives the computer the ability to quickly and directly access values anywhere in memory. In order for the memory to stay active and available, it must be supplied electricity from the power supply, which is why if you turn off a computer data stored in memory is lost. Data in memory that you wish to save must be placed onto a hard disk drive (HDD) or other storage device where it will stay until deleted.

### Hard Disk Drive

A hard disk drive (HDD) is a long-term, persistent storage device that can store large amount of data. It serves as the primary storage for computers to access and store data or files. Such files as pictures, music, videos, spreadsheets, documents, databases, etc. Most HDD contains hundreds of gigabytes (GB) or more. Hard disk drives are slower than system memory for data access, but they are also significantly cheaper. Any information that is saved to a hard disk drive is persistent and will not be lost even if the computer is turned off. The same applies for flash drives that serve as portable data storage that is accessible from any computer the drive is plugged into.

### Solid State Drive

Solid state drives (SSD) are the next technological evolution of the HDD. SSDs, unlike HDDs, do not contain any moving parts, making them cooler, faster, safer, and silent. SSDs utilize a non-volatile, persistent version of flash memory, more specifically, NAND-based flash memory, which, unlike the flash memory in RAM, retains data when it loses power. There are a few downsides to SSDs though. Currently, SSDs come in much smaller sizes and are orders of magnitude more expensive than HDDs of the same size. As SSD technology matures, this is expected to change and, recently, consumer SSDs have significantly dropped in price.

### Video Card

A video card is a type of expansion card, or circuit board, that can be inserted into a computer's motherboard to add functionality. Video cards are used to produce a supply of output signals which are fed into a display to produce images. The video card's subcomponents include a processing unit, memory, connections to a display device, and a heat sink. A video card typically consists of these components mounted on a printed circuit board. Video cards for desktop computers come in one of two size profiles, regular and low profile. These profiles are based on width only, while the length and thickness of the video card may vary. Most video cards allow access to advanced graphics like 2D and 3D images, gaming, and other video output.
It should be noted that most modern motherboards come with an integrated video card, eliminating the need to buy a separate component. However, purchasing a separate video card typically provides a much higher level of performance in terms of image quality.

### Input Devices

Input devices are any form of computing hardware that is used to provide and use data in order to control signals and commands for an information system such as a computer. Examples of things that could be classified as input devices are keyboards, mouses, or joysticks.

### Output Devices

Output Devices are devices that receive data from a computer and convert the data into human-accessible physical forms such as text, audio, or video. Common output devices include monitors, which convert data from a computer into a readable display, printers, which convert data into physical reproductions, and speakers, which convert computer data into audio.

### Casings

A computer case is the box that contains most of what a computer is composed of. It is also known as a tower, base unit, housing and etc. It protects a computer's inner workings and makes transporting it a lot easier. It can come in many different shapes and sizes, but it usually depends on the size of the motherboard. In fact, the motherboard, along with the power supplies and computer case, must all be compatible in order for them to function together. The cases are usually made from aluminum or steel, but other materials include glass, wood, or plastic.

### Mainframe Computer

The mainframe computer is a monumental computer in comparison to a normal computer. Usually large in size, they have the potential to encompass an entire room. Mainframe computers are a vast amount more costly than personal computers also; the prices are potentially hundreds of times as that of a generic computer. Their sole purpose is to handle tremendous calculations for big companies and governments. The census bureau uses such computers for the vast amount of information needed each year for the census of the general population. Federal and private banks also use These computers for the processing of transactions and other number related endeavors.

## Units of Information

There are different ways to measure stored information. The smallest unit of information is known as a bit. A bit can have either the value of 1 or 0. From there, a group of 4 bits is called a nibble which is half a byte. A byte used to be the number of bits used to encode text on a computer. Now In today's age a byte is 8 bits or an "octet". Then kilobyte, megabyte, and gigabytes are other familiar units of information.