System Unit Types Desktop System Units Media Center System Units Notebook System Units Tablet PC System Units Handheld Computer System Units Six basic types of system units Desktop – electronic components and selected secondary storage Horizontal models Vertical models or tower models Media center – use powerful desktop system hardware with specialized graphic cards Notebook – components, secondary devices, and input devices – often called laptop computers (Key Term) Netbook – like notebooks, but less powerful and less expensive Tablet PC (Key Term) – supports the use of a stylus or pen to input commands and data Convertible tablet PC (Key Term) – notebook computer with monitor that swivels/folds Slate tablet PC– similar to notebook but monitor is attached to the system unit and does not have an integrated keyboard Hand-held computer systems Personal digital assistant (Key Term) (PDA) – electronic components, secondary storage, input/output devices Palm computers - contain an entire computer system System unit is also referred to as the system cabinet (Key Term)

System Unit Also known as the system cabinet is a container that houses most of the electrical components that make up a computer system. System Chassis, System Board (Motherboard), Microprocessor, Memory, Socket, Bus Lines, and Expansion Slots

Electronic Data and Instructions Data and instructions are represented electronically Two-state system or Binary System Off/On electrical states Characters represented by 0’s (off) and 1’s (on) Bits Bytes Our voices recognize analog (Key Term) signals Continuous signals Computers only recognize digital (Key Term) signals Electrical On/off state The binary system consists of two digits – 0 and 1 Each 0 or 1 is called a bit – short for binary digit Bits are combined into groups of eight bits called bytes Smallest character = bit; eight bits = 1 byte or one character

Character Coding Schemes Three types of binary coding schemes ASCII - American Standard Code for Information Exchange EBCDIC - Extended Binary Coded Decimal Interchange Code Unicode - handles languages with large numbers of characters Knowing this information helps understand what takes place when data entered into computer – why it takes “so long” for the data to get transformed Three basic schemes of coding ASCII – primarily desktop EBCDIC – primarily mainframe and super Unicode – to handle languages with large numbers of characters

System Board Connects all components Allows communication between devices Main board or motherboard Circuit board components Sockets Slots Bus lines Connects all system components and allows input and output devices to communicate with system unit Other names: main board; motherboard Located in the system unit, consists of a large flat circuit board with sockets and chips (Key Term) Chips contain numerous circuits etched on a small wafer of layers of silicon and other materials Chips are mounted on carrier packages (Key Term) Chips are also referred to as a silicon chip (Key Term), semiconductor (Key Term), or integrated circuit (Key Term)

Microprocessor Chips Central Processing Unit (CPU) Measurement units for processing speed (shown here) Two Basic Components Control unit Arithmetic-logic unit (ALU) Located on the microprocessor chip and has two components - the control unit and the arithmetic-logic unit Control Unit Program instructions Directs flow between memory and Arithmetic-Logic Unit Directs flow between CPU and I/O devices Arithmetic-Logic Unit - ALU Two types of operations Arithmetic operation (Key Term) Logical operation (Key Term) Microprocessor Chips Word size Smart Card (Key Term)

Microprocessor Chips Chip capacities are expressed in word sizes Two significant developments 64-bit processors Have become standard for most of today’s desktop and laptop computers Multi-Core Chips Can provide two separate and independent CPUs Parallel Processing A word (Key Term) is the number of bits that can be accessed at one time by the CPU Older computers process data and instructions in millionths of a second – microseconds Newer computers Nanoseconds– microcomputers Picoseconds– supercomputers

Specialty Processors Coprocessors Designed to improve specific computing operations Graphics coprocessors Smart cards Credit card sized with an embedded chip Used by many universities Specialty processors in cars As many as 70 Used to control features RFID tags Information chips Used for tracking purposes Specialty processors are designed to handle special functions Graphics Displaying and manipulating 2-D and 3-D graphics images Smart cards (and readers) Plastic cards that have an embedded chip Can store 80 times the information stored on the magnetic strip of a regular credit card RFID tags Used by luxury car manufacturers for fuel efficiency, tracking, and satellite entertainment

Memory Holding area for data, instructions, and information Memory is contained on chips connected to the system board Types of memory chips RAM – Programs and data ROM – Fixed start-up instructions Flash – Flexible start-up instructions RAM (Random-access memory) (Key Term) Frequently accessed Acts as high-speed, temporary holding area Faster processing results Temporarily holds data and programs being processed by the CPU Volatile - when power shuts off, contents of RAM are emptied Exception - flash RAM can retain data when power disrupted, used in high end portable computers Cache (pronounced: “cash”) Area in RAM set aside to store information frequently accessed Acts as a high-speed, temporary holding area for parts of programs and data Results in faster processing results for the user ROM (Read-only memory) (Key Term) Nonvolatile; CPU retrieves programs written on the ROM chip Typical user does not go in and change information on ROM Also called firmware Flash Flash (Key Term) memory offers a combination of the features of RAM and ROM. Like RAM, it can be updated to store new information. Like ROM, it does not lose that information when power to the computer system is turned off.

RAM Random Access Memory (RAM) chips hold the program and data Cache memory or RAM cache Flash RAM or flash memory Other types of RAM DRAM SDRAM DDR Direct RDRAM Cache memory – improves processing by acting as a temporary high-speed holding area between the memory and CPU Flash memory – can retain data even if the power is disrupted Most expensive type of RAM Used for digital telephones, digital video cameras, and portable computers Virtual Memory (Key Term) – large programs are divided into parts and the parts are stored on a secondary device, usually a hard disk. Each part is then read into RAM only when needed RAM is also referred to as temporary or volatile storage It is a good idea to save your work in progress to a second a secondary storage device. which is permanent or nonvolatile storage Return

ROM Read-only memory (ROM) chips are not volatile and cannot be changed by the user CPU can read, or retrieve data and programs but the computer cannot write Contain special instructions Needed to start a computer Give keyboard keys their special capabilities Put characters on screen ROMs are also called firmware Return

Flash Flash memory offers a combination of the features of RAM and ROM. Flash memory is used for a wide of range of applications. If changes are made to the computer system, these changes are reflected in flash memory. Return

Expansion Slots and Cards Allows for new devices to be added Open architecture Slots provide for expansion Expansion cards are also called Plug-in boards Controller cards Adapter cards Interface cards Expansion slots provide an open architecture Expansion cards provide network connections, PC/TV combinations, and more This open architecture allows users to expand and update their systems Devices to meet these needs, expansion cards, are inserted into the expansion slots A closed architecture card relies on a proprietary add-on, often at more expensive prices

Commonly Used Expansion Cards Graphics cards Sound cards Network interface cards (NIC) Wireless network cards PC cards & Express cards TV tuner cards Graphics cards - connect the system board to the monitor; convert internal electronic signals to video signals Sound cards – convert electronic signals to audio signals and accept audio input from microphones Modem cards – allow distant computers to communicate with each other by converting computer electronic signals to travel over phone lines Network adapter cards (Key Term) (NICs or Network Interface Cards) - connect system unit to a cable (Key Term) attached to a network TV turner cards (Key Term) - PC/TV combination cards led to high audio quality systems called home PCs TV tuner converts video signal for viewing on computer monitor PC cards - credit card-sized expansion cards for portable computers, also known as PCMCIA (Personal Computer Memory Card International Association) cards

Bus Lines Connect parts of the CPU to each other Data roadway for traveling bits Measured as bus width More lanes, faster traffic Two basic categories System buses Expansion buses Bus lines provide data pathways that connect various system components A bus line is also called a bus (Key Term) It is a pathway for bits representing data and instructions Every computer has two basic categories of buses System – connects the CPU to memory on the system board Expansion – connects the CPU to slots on the system board

Expansion Buses Connects the CPU to other components on the system board, including expansion slots Principal types Peripheral Component Interconnect (PCI) Universal serial bus (USB) FireWire buses Serial Advanced Technology Attachment (SATA) PCI Express (PCIe) Remember that architecture determines whether or not new devices can be easily added Industry Standard Architecture (ISA) – developed for IBM PC 8 bits then expanded to 16 bits, although slow, still widely used Peripheral Component Interconnect (PCI) – originally for video demands of GUI (graphical user interfaces); widely used to connect CPU, memory, and expansion boards; either 32 or 64 bit, more than twenty times faster than an ISA Universal serial bus (USB) – gradually replacing serial and parallel ports (Key Term) Faster than AGP bus New version is USB 2.0 FireWire buses – High-performance serial bus (HPSB) – operate much like the USB buses and perform at speeds comparable to USB 2.0 Used with digital camcorders Used with video editing software SATA - - newest bus; It is much faster than USB 2.0 and FireWire buses and is now widely used to connect high-speed storage devices to the system board. PCI Express – widely used I many of today’s most powerful computers; provides a single dedicated path for each connected device; now replacing the PCI bus.

Ports Socket for connecting external devices Ports can connect directly to the system board or they can connect to cards that are inserted into slots on the system board Three Types Standard Ports Legacy Ports Specialized Ports Ports are connecting sockets on the outside of a system unit Ports are often standard features of computer systems and others are more specialized

Standard Ports Four common ports VGA USB ports FireWire ports Ethernet ports Four common ports USB ports (universal serial bus) – gradually replacing serial and parallel ports; can connect multiple devices; faster than parallel FireWire ports also known as high performance serial bus (HPSB) ports – for high-speed printers and video cameras; as fast as USB 2.0 Return

Legacy Ports Serial ports Parallel ports Keyboard and mouse ports Infrared data association (IrDA) Game ports Serial ports – data transported one bit at a time; mouse, keyboard, modem, etc. Parallel ports – for external devices needing lots of data over short distances, like printers, scanners, external Zip drives Keyboard and mouse IrDA – were used to provide wireless mechanisms for transferring data between devices; for example, transferring data from a handheld to a desktop Return

Specialized Ports Three specialized ports Musical Instrument digital interface (MIDI) Sony/Philips Digital Interconnect Format (S/PDIF) High Definition Multimedia Interface (HDMI) MIDI – special type of serial port for connecting musical instruments S/PDIF – also known as optical audio connections; these ports are used to integrate computers into high-end audio and hone theatre systems HDIM – provide high definition video and audio Return

Cables Used to connect external devices to the system unit via the ports One end of the cable is attached to the device and the other end has a connector that is attached to a matching connector on the port

Power Supply Computers require direct current (DC) DC power provided by converting alternating current (AC) from wall outlets or batteries Desktop computers use power supply units Notebooks and handhelds use AC adapters Cables are used to connect exterior devices to the system unit via the ports Direct current (DC) powers computers Desktop computers have a power supply unit located within the system unit Notebook computers use AC adapters that are located outside the system unit