SYSTEM UNIT

RAM

It is a type of computer memory that provides direct access to any single location (any byte). RAM chips are "byte addressable." The contents of any byte can be read or written without regard to the bytes before or after it. The term generally refers to main memory, which is the computer's workspace, and the most common type of RAM is the DRAM chip. RAM read and write speeds are generally the same, taking no longer to write a byte than it does to read one.

CACHE MEMORY

Cache is the small amount of memory that is normally less then 1MB that resides on the CPU so that the time to access the main memory is reduced. Cache memory stores the copies of the most frequently used data and when the user requests to access a certain portion of the maim memory, the computer will check cache memory first and load it immediately if it is resent in the cache memory thereby reducing the access time. If it is not present in cache then it will load from the main memory and this involves latency.

ROM

Form of computer memory that does not lose its contents when the power supply is cut off and that is not rewritable once it is manufactured or written. It is generally employed for programs designed for repeated use without modification, such as the start-up procedures of a pc, the ROM is used for storing the program used in the control unit of the computer.

FLASH MEMORY

A very popular non-volatile, rewritable memory chip used for storage. Extremely durable, flash memory is used in myriad portable devices, including digital cameras, digital music players, smartphones and tablet computers. USB drives "are" flash memory chips, and the solid state drives (SSDs), which are increasingly replacing hard disks in laptops, are also flash memory chips.

GRAPHIC CARD

Graphics cards are PCBs (printed circuit boards) that perform the dual role of sending pixels to the display and providing a specific type of processing using a GPU (graphical processing unit).
One of the main features of a graphics card is the ability to draw 3D graphics in realtime using a technique called rasterization. This involves converting 3D coordinates into areas of pixels and filling the areas with either a transformed image called a texture or a flat surface.

Most graphics cards can perform a technique called "Hardware Transform and Lighting", which means the 3D movement and illumination of triangle surfaces is handled by the card rather than using the CPU and making frequent use of buses.
A more recent addition to the capabilities of graphics cards is shader processing, which allows a game programmer to write special programs called shaders that have control over the way the GPU transforms coordinates and images.

When buying a graphics card, common indications of performance are triangles per second, texture fill rate, shader cores, GPU clock speed and memory clock speed. Other attributes that are likely to dictate which card to buy are form factor and power consumption.
Graphics cards follow standard interfaces, such as PCI-E, PCI or AGP, meaning they are common attachments for desktop computer motherboards.

SOUND CARD

Also called a "sound board" or "audio adapter," it is a plug-in card that records and plays back sound. Supporting both digital audio and MIDI, sound cards provide an input port for a microphone or other sound source and output ports to speakers and amplifiers. Sound circuits are typically built into the chipset on the motherboard, but can be disabled if a separate sound card is installed.

Digital audio files contain soundwaves converted into digital form. Sound cards convert the digital samples back into analog waves for the speakers using digital signal processing (DSP).

MIDI files contain a coded representation of the notes of musical instruments such as middle C on the piano. Taking considerably less space than digital audio, MIDI files require a wavetable synthesizer on the card, which holds digitized samples of the instruments.

NETWORK INTERFACE CARD

Pronounced "nick," this is the card that physically makes the connection between the computer and the network cable. These cards typically use an Ethernet connection and are available in 10, 100, and 1000 Base-T configurations. A 100 Base-T card can transfer data at 100 Mbps. The cards come in ISA and PCI versions and are made by companies like 3Com and LinkSys. So if you want to connect your computer to a network, you better get yourself a NIC.

PLUG AND PLAY

The ability to add a new component to a system and have it work automatically without having to do any technical analysis or manual configuration. A standard from Intel for peripheral expansion on a PC. On starting up the computer, Plug and Play (PnP) recognizes the attached peripheral devices and adjusts the appropriate internal settings, namely configuring the IRQ, DMA and I/O address.

SERIAL PORT

The serial port is a type of connection on PCs that is used for peripherals such as mice, gaming controllers, modems, and older printers. It is sometimes called a COM port or an RS-232 port, which is its technical name. If that's not enough to confuse you, there are two types of serial ports -- DB9 and DB25. DB9 is a 9-pin connection, and DB25 is, you guessed it, a 25-pin connection.

A serial port can only transmit one bit of data at a time, whereas a parallel port can transmit many bits at once. The serial port is typically the slowest port you'll find on a PC, if you find one at all. Most newer computers have replaced serial ports with much faster and more compatible USB ports.

PARALLEL PORT

A hardware interface that transfers one or more bytes simultaneously. A socket on a computer used to connect a printer or other device via a parallel interface (eight data bits transferring simultaneously). In the past, the parallel port was widely used for printers and occasionally for connecting other devices externally, but was superseded by USB.

UNIVERSAL SERIAL BUS PORT (USB)

The most widely used hardware interface for attaching peripherals to a computer. There are typically at least two USB ports on laptops and four on desktop computers, while USB "hubs" allow many more connections (see below). After appearing on PCs in 1997, USB quickly became popular for connecting keyboards, mice, printers and hard drives, eventually replacing the PC's serial and parallel ports.

USB devices are "hot swappable;" they can be plugged in and unplugged while the computer is on. This feature, combined with easy-to-reach ports on the front of the computer case, gave rise to the ubiquitous flash drive for backup and data transport

FIREWALL PORT

A firewall port, directly relates to an IP port. Sometimes you will need to ‘open a port’ in your firewall protection or router for a program to operate. Most programmers these days are aware that people use firewalls and routers so they try to make their software fully compatible with them. There are occasionally still programs that need some manual configuration. This is most often the case when you try to run a ‘server’ on your home network. Some of the most common servers that people like to run are game servers.

ETHERNET PORT

it's the same thing as a network port. looks like a telephone jack, but bigger. should be in the back of the system, and will probably have a symbol above it that looks like 3 boxes with lines connecting them.

HIGH DEFINITION MULTIMEDIA INTERFACE

It is a specification that combines video and audio into a single digital interface for use with digital versatile disc (DVD) players, digital television (DVT) players, set-top boxes, and other audiovisual devices. The basis for HDMI is High Bandwidth Digital Content Protection (HDCP) and the core technology of Digital Visual Interface (DVI). HDCP is an Intel specification used to protect digital content transmitted and received by DVI-compliant displays.