The Visible Computer Components

computer cases: several versions of the tower model

*Full tower* used for servers or when you will be installing many drives and other components *Mid tower* a slightly smaller version of the full-size tower *Micro, or mini tower* the size that replaces the original desktop case in most modern systems *Slim line* a tower case that can be turned on its side to save room.

Two types of memory

*Random Access Memory* (RAM): a computer storage method that functions as a computer's main memory -This type requires a constant power source to access the data stored within the RAM *Read- Only Memory* (ROM): data stored on ROM is saved and stored without a constant power source -Once data is written to ROM, it *cannot be modified easily*

riser cards

*a board that plugs into the motherboard and provides additional expansion slots for adapter cards* Because it rises above the motherboard, it enables you to connect additional adapters to the system in an orientation that is parallel to the motherboard and thus saves space within the system case commonly found within *rackmount server implementations* to provide additional slots for expanding the features of a server and in low rise smaller cases to fit larger expansion cards *A riser card expands motherboard capabilities the way a power strip increases the capabilities of electrical outlets*

The Power-On Self Test (POST)

*a built-in diagnostic program that runs every time a personal computer starts up* checks your hardware to ensure that everything is present and functioning properly, before the system BIOS begins the operating system boot process -If there is an error, then an audible beep will alert you that something is wrong The POST process contains several steps to ensure that the system meets the necessary requirements to operate properly *Note*: The POST process can vary a great deal from manufacturer to manufacturer

central processing unit (CPU)

*a computer chip where most of the computing calculations take place* On most computers, the CPU is housed in a single microprocessor module that is installed on the system board in a slot or a socket.

Common Computer Components: The System Unit

*the main component of a computer, which houses most of the other devices that are necessary for the computer to function* -comprises a chassis and internal components, such as the system board, the microprocessor, memory modules, disk drives, adapter cards, the power supply, fans and other cooling systems, and ports for connecting external components such as monitors, keyboards, mice, and other devices System units are also often referred to as *boxes, main units, or base units*. In some newer computer models, the system unit is incorporated with the display screen and referred to as an all-in-one computer

the motherboard

*the personal computer component that acts as the backbone for the entire computer system* - Sometimes called the *system board* it consists of a large, flat circuit board with chips and other electrical components on it, with various connectors Some components are soldered directly to the board, and some components connect to the board by using slots or sockets

the system bus

*the wires, or traces, on the motherboard that provide the main communication path between the CPU and memory* -enables data transfer between the CPU, memory, and the other buses in the computer, which connect other system components such as hard drives and adapter cards -sometimes referred to as the frontside bus or local bus In computer communications, a bus is: *a group of wires or electronic pathways that connect components*

The POST process

1) *Hardware Component* Power supply *POST Test Criteria* Must be turned on, and must supply its power good signal 2) *Hardware Component* CPU *POST Test Criteria* Must exit Reset status mode, and must be able to execute instructions 3) *Hardware Component* System firmware *POST Test Criteria* Must be readable 4) *Hardware Component* System firmware memory Must be readable 5) *Hardware Component* Memory *POST Test Criteria* .Must be able to be read by the CPU, and the first 64 KB of memory must be able to hold the POST code 6) *Hardware Component* Input/output (I/O) bus or I/O controller *POST Test Criteria* Must be accessible, and must be able to communicate with the video subsystem

UEFI firmware advantages over a traditional BIOS system

• Ability to boot from large disks (over 2 TB) with a GUID Partition Table (GPT) • CPU-independent architecture and drivers • Flexible pre-OS environment, including networking capabilities • Modular design

power supplies

*a computer system component that converts line-voltage alternating current (AC) power from an electrical outlet to the low-voltage direct current (DC) power needed by other system components* often referred to as the power supply unit (PSU) -typically a metal box in the rear of the system that is attached to the computer chassis and to the system board *it is required in order for system components to receive power* contains the power cord plug and a fan for cooling, because it generates a lot of heat -Some power supplies have a voltage selector switch that enables you to set them to the voltage configurations that are used in different countries *AC adapters are generally built in to the power supply for desktop systems and are external for laptops and other mobile systems*

cooling systems

*a computer system component that prevents damage to other computer parts by dissipating the heat generated inside a computer chassis* The cooling system can consist of one or more fans and other components such as *heat sinks* or *liquid cooling* systems that service the entire computer as well as individual components, such as the power supply and CPU

storage devices

*a computer system component, such as a hard drive, that enables users to save data for reuse at a later time, even after the personal computer is shut down and restarted* these devices can save data magnetically, optically, or electronically, depending on their design

daughter boards

*a general computing and electronics term for any circuit board that plugs into another circuit board* In personal computing, it can be used as a more general term for adapter cards Sometimes, in casual usage, the term "daughter board" is used interchangeably with the term "riser card," but technically *they are not the same*

Common Computer Components: input devices

*a personal computer component that enables users to enter data or instructions into a computer* common devices include keyboards and computer mice -can connect to the system unit via a cable or a wireless connection

Common Computer Components: display devices

*a personal computer component that enables users to view the text and graphical data output from a computer* -commonly connect to the system unit via a cable, and they have controls to adjust the settings for the device -vary in size and shape, as well as the technologies used *Common terms display, monitor, screen, liquid crystal display (LCD), and flat-panel monitors*

expansion cards

*a printed circuit board that you install into an expansion slot on the computer's system board to expand the functionality of the computer* In standard desktop systems, cards have connectors that fit into an expansion slot on a system board and circuitry to connect a specific device to the computer -Laptops, on the other hand, typically have slots located on the outside of the case for inserting expansion cards *laptop expansion cards* *Note*: An expansion card is also known as an adapter card, I/O card, add-in, add-on, or simply as a board.

The Systems Basic Input/Output System (BIOS)

*a set of instructions that is stored in ROM and that is used to start the most basic services of a computer system* Every computer has this system, which sets the computer's configuration and environment when the system is powered on -It is located in ROM chips on the system board -Computers may also include other devices that have their own BIOS to control their functions

Unified Extensible Firmware Interface (UEFI)

*a standard firmware interface for PCs that was designed to improve software interoperability and address the limitations in BIOSs* Providing legacy support for BIOS services, this can *support remote diagnostics and repair of computers*, even *without an operating system being installed*

peripheral devices

*provide alternative input or output methods or additional data storage* Also called external devices -enhances the functionality of practically any personal computer by connecting different types of these devices to the system unit -You connect these devices to the system unit via cable or a wireless connection Some devices have their own power source, while others draw power from the system (*examples:* microphones, cameras, speakers, scanners, printers, and external drives)

nonvolatile memory

*retains the information stored on it whether or not electrical current is available* ROM is an example of non-volatile memory

firmware

*specialized software stored in memory chips that stores OS-specific information whether or not power to the computer is on* most often written on an electronically reprogrammable chip so that it can be updated with a special program to fix any errors that might be discovered after a computer is purchased, or to support updated hardware components *flashing*: Updating firmware electronically

volatile memory

*stores data temporarily and requires a constant source of electricity to keep track of the data stored in it* When the power is no longer available, the data stored in volatile memory is lost -The computer can both read the data stored in RAM and write different data into the same RAM *Any byte of data can be accessed without disturbing other data, so the computer has random access to the data in RAM*

memory

*the computer system component that provides a temporary workspace for the processor* -refers to modules of computer chips that store data in a digital electronic format, which is faster to read from and write to than tape or hard drives Memory chips each contain millions of transistors etched on one sliver of a semiconductor *Transistors*: switches that can be opened or closed -When a transistor is *closed*, it conducts electricity, representing the binary *number 1* -When it is *opened*, it does not, representing the binary *number 0*

computer cases

*the enclosure that holds all of the components of your computer* comes in several sizes and arrangements -Some are designed to hold many internal components and have a lot of room to work around those components. Other cases are designed to use a minimum amount of space The trade-off is that the interior of the case is often cramped, with little room for adding additional components