Five Key Computer ComponentsFive Key Computer Components

Central Processing UnitCentral Processing Unit Memory Memory Input/Output (I/O) DevicesInput/Output (I/O) Devices Disk StorageDisk Storage ProgramsPrograms

Central Processing UnitCentral Processing Unit

Executes instructions (programs)Executes instructions (programs) To do this the CPU can:To do this the CPU can:

– read/write information in memoryread/write information in memory– recognize difference between instruction and recognize difference between instruction and

datadata– control I/O devicescontrol I/O devices

MemoryMemory

Also known as Primary StorageAlso known as Primary Storage Provides temporary storage of programs Provides temporary storage of programs

and dataand data Can be accessed directly by CPU or through Can be accessed directly by CPU or through

I/O devicesI/O devices

Input/Output DevicesInput/Output Devices

MouseMouse KeyboardKeyboard Video DisplayVideo Display PrinterPrinter ModemModem Communication Lines (Networks)Communication Lines (Networks)

Disk StorageDisk Storage

Also known as secondary storageAlso known as secondary storage Provides permanent (non-volatile) storage Provides permanent (non-volatile) storage

of programs or data.of programs or data.

ProgramsPrograms

System SoftwareSystem Software– BIOS- Basis Input/Output Services (ROM)BIOS- Basis Input/Output Services (ROM)– Operating System - DOS, Windows, UnixOperating System - DOS, Windows, Unix

Application SoftwareApplication Software– Word ProcessorsWord Processors– DatabaseDatabase– etcetc

More PC Hardware TermsMore PC Hardware Terms

serial - all information goes one bit at a time serial - all information goes one bit at a time over the same wire.over the same wire.

parallel - bits go over many wires running parallel - bits go over many wires running side by side.side by side.

clock - sends pulses to synchronize the CPU clock - sends pulses to synchronize the CPU and other hardware.and other hardware.

MHz - megahertz, one million clock pulses MHz - megahertz, one million clock pulses per second.per second.

Main Hardware ComponentsMain Hardware Components

System UnitSystem Unit Display Display KeyboardKeyboard MouseMouse

System UnitSystem Unit

System Board (Mother board)System Board (Mother board)– Central Processing Unit (CPU)Central Processing Unit (CPU)– Memory (RAM - Random Access Memory)Memory (RAM - Random Access Memory)– ROM (Read-only Memory)ROM (Read-only Memory)– Expansion SlotsExpansion Slots– Math Co-processor Math Co-processor

» 486 and 586 CPU has integrated Math co-processor.486 and 586 CPU has integrated Math co-processor.

PC Expansion BusPC Expansion Bus

Connects CPU to circuit boards which Connects CPU to circuit boards which control devices such as disk drives, printer, control devices such as disk drives, printer, display, modems, etcdisplay, modems, etc

ISA: Industry Standard Arch.ISA: Industry Standard Arch.

Commonly known as AT bus.Commonly known as AT bus. 8 or 16 bit data bus, 98-pin expansion 8 or 16 bit data bus, 98-pin expansion

connector.connector. Can access up to 16 MB of memory.Can access up to 16 MB of memory. Common and cheap but very slow (8Mhz).Common and cheap but very slow (8Mhz).

MCAMCA

Micro Channel ArchitectureMicro Channel Architecture Designed by IBM to replace ISA in PS/2 Designed by IBM to replace ISA in PS/2

system.system. not compatible with ISA bus boards.not compatible with ISA bus boards. 16 and 32 bit versions.16 and 32 bit versions. Not seen much anymore.Not seen much anymore.

EISAEISA

Extended Industry Standard ArchitectureExtended Industry Standard Architecture designed by Compaq and other clone designed by Compaq and other clone

companies as alternative to MCAcompanies as alternative to MCA Allows use of ISA bus boards in new Allows use of ISA bus boards in new

computers.computers.

Local BusLocal Bus

Communicates at system speedCommunicates at system speed Memory, display, disk drives all can use Memory, display, disk drives all can use

local bus.local bus. Provides 32 or 64 bit data access.Provides 32 or 64 bit data access.

Local Bus StandardsLocal Bus Standards

VESA VL Bus - (Video Electronics Standards VESA VL Bus - (Video Electronics Standards Association)Association)– First to gain popularityFirst to gain popularity

– 32 bit bus running at 33 MHz can handle up to 107 32 bit bus running at 33 MHz can handle up to 107 Mbytes/secondMbytes/second

PCI (Peripheral Component Interconnect)PCI (Peripheral Component Interconnect)– 32 bit bus running at 33 MHz can handle up to 132 32 bit bus running at 33 MHz can handle up to 132

Mbytes/secondMbytes/second

– faster and more easily expanded than VESA busfaster and more easily expanded than VESA bus

SCSISCSI

pronounced “scuzzy”pronounced “scuzzy” used with printers, hard disks, tape drives.used with printers, hard disks, tape drives. excellent for high-speed data transfer in excellent for high-speed data transfer in

multi-user systems or file servers.multi-user systems or file servers. Can handle up to 7 devices on one adaptor Can handle up to 7 devices on one adaptor

card.card.

GatesGates

Fundamental building block of all digital logic circuits. Logic functions are implemented by the interconnection of gates. An electronic circuit that produces an output signal that is a simple

Boolean operation on the input signals. The basic gates are: AND, OR, NOT, NAND, NOR.

Basic gates have either one or two input lines and a single output line.

When the signals on the input lines change, the correct output signal is generated by the gate, almost simultaneously, delayed only by the propagation time of the signals through the gate (called gate delay).

Name Graphic Symbol Algebraic Function Truth Table

A B F

0 0 0

0 1 0

1 0 0AND

F = A B

also F = AB

1 1 1

A B F

0 0 0

0 1 1

1 0 1

OR F = A + B

1 1 1

A F

0 1NOT

F = A

also F = A’ and F = A

1 0

A B F

0 0 1

0 1 1

1 0 1

NANDF = (AB)

1 1 0

A B F

0 0 1

0 1 0

1 0 0

NOR F = (A + B)

1 1 0

Boolean OperationsBoolean Operations

MultiplexersMultiplexers

A multiplexer connects multiple inputs to a single output. At any A multiplexer connects multiple inputs to a single output. At any given time, one of the inputs is selected and is passed directly to the given time, one of the inputs is selected and is passed directly to the output. Multiplexers are used in digital circuits to control signal and output. Multiplexers are used in digital circuits to control signal and data routing. Shown below is a block diagram of a 4-to-1 multiplexer. data routing. Shown below is a block diagram of a 4-to-1 multiplexer. There are four input lines labeled D0, D1, D2, and D3 of which one is There are four input lines labeled D0, D1, D2, and D3 of which one is selected to provide the output signal F. To select one of the four input selected to provide the output signal F. To select one of the four input signals, a 2-bit selection code is required and this is implemented as signals, a 2-bit selection code is required and this is implemented as the two select lines labeled S1, and S2.the two select lines labeled S1, and S2.

MultiplexersMultiplexers

DecodersDecoders

A decoder is a combinational circuit which has a number of output lines, of which only one is valid (asserted) at any time, dependent upon the pattern on the input lines. In general, a decoder has n input lines and 2n output lines. Decoders are heavily used in digital computers for address decoding.

DecodersDecoders