Hardware Basics:

Inside the

Box

2

 2001 Prentice Hall

2.2

Chapter Outline

“There is
no
invention
– only
discovery.
”

Thomas J. Watson,

Sr.



What Computers Do



A Bit About Bits



The Computer’s Core:
CPU and Memory

 2001 Prentice Hall

2.3

What Computers Do

Receive input

Process

Information

Produce Output

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2.4

What Computer Do

Store

Information

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2.5

Input Devices

• Computers accept

information from the

outside world

• The keyboard is the

most common input

device

• Pointing devices like

the mouse also

receive input

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2.6

Output Devices

• Computers produce

information and send it

to the outside world.

• A video monitor is a

common output device.

• Printers also produce

output.

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2.7

Process Information

• The processor, or

central processing
unit (CPU), processes
information and
performs all the
necessary arithmetic
calculations.



The CPU is like the
“brain” of the
computer.

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2.8

Store Information

• Memory and storage

devices are used to
store information



Primary storage is
the computer’s
main memory



Secondary storage
uses disks or other
media

Inp

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es

Ou

tpu

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dev

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s

Processo

rs

Storag
e

Hardware

 2001 Prentice Hall

2.10

Information

Information comes in many forms



Words . . . Numbers . . .
Pictures . . . Sounds



Computers only understand
information in digital form



Information must be
broken into bits

 2001 Prentice Hall

2.11

A Bit About Bits

• A bit (binary digit)

– is the smallest unit of

information

– can have two values
– can represent numbers,

codes, or instructions



Think of these values as
switches: yes and no, black
and white, high and low, or
onand of

Of

On

“

Even the

most
sophisticate
d ocmputer
is really
only a large
well-
organized
volume of
bits.”

David Harel

 2001 Prentice Hall

2.12

More about Bits

• Each switch can be used to store a

tiny amount of information, such as:

– An answer to a yes/no question
– A signal to turn on a light

• Larger chunks of information are

stored by grouping bits as units

– 8 bits (byte) = 256 diferent

messages

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2.13

Bits as Codes

• ASCII - American

Standard Code for
Information
Interchange

– most widely used

code, represents each
character as a unique
8-bit code.

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2.14

Bits as Instructions

• The computer stores programs as

collections of bits.

– For instance, 01101010 might instruct

the computer to add two numbers.

• Other bit instructions might include

where to find numbers stored in
memory or where to store them.

 2001 Prentice Hall

2.15

Bits, Bytes, and

Buzzwords

• Common terms might describe file

size or memory size:

– Bit: smallest unit of information
– Byte: a grouping of eight bits of

information

– K: (kilobyte); about 1,000 bytes

of information - technically
1024 bytes equals 1K of storage.

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2.16

Bits, Bytes, and

Buzzwords

MB: (megabyte): about 1 million
bytes of information

GB: (gigabyte): about 1 billion
bytes of information

TB: (terabyte): about 1 million
megabytes of information

 2001 Prentice Hall

2.17

The Computer’s Core:

The CPU and Memory

• The transformations

are performed by the
CPU - the central
processing unit or
processor.

• The microprocessor,

which is a silicon
chip, is located on
the motherboard.

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2.18

The CPU:

The Real Computer

When purchasing a computer,

selecting a CPU is very important.
The two most critical factors are:

Compatibility

Speed

 2001 Prentice Hall

2.19

Compatibility

• Not all software is compatible with any

given CPU. Each computer has a unique
instruction set - a vocabulary of
instructions the processor can execute.

• New microprocessors can usually run

older software, but new software is not
usually compatible with old
microprocessors.

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2.20

Speed

• The computer’s speed is

measured by the speed
of its internal clock - a
device to synchronize
the electric pulses.



Speed is measured in units
called megahertz (mHz).

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2.21

Speed

• A computer’s speed cannot be judged

by megahertz alone.



Speed is also determined by the
architecture of the processor – how
individual components of the CPU are put
together on the chip.



Newer chips can manipulate more bits

simultaneously than older chips.



Typically a CPU can process between 16 to 64

bits.

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2.22

Speed



Manufacturers have switched from

CISC

to

RISC

processors so tasks

can be performed faster.



CISC

- complex instruction set

computer



RISC

- reduced instruction set

computer

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2.23

Speed

•

Parallel processing

places multiple

processors in a

computer.

• Most supercomputers

have multiple

processors that divide

jobs into pieces and

work in parallel on the

pieces.

 2001 Prentice Hall

2.24

The Computer’s Memory

RAM

(random access memory):

– is the most common type of primary

storage, or computer memory

– is used to store program instructions and

data temporarily

– unique addresses and can be stored in any

location

– can quickly retrieve information
– will not remain if power goes of (volatile)

 2001 Prentice Hall

2.25

The Computer’s Memory

•

ROM

(read-only memory):

– information is

stored permanently
on a chip.

– contains startup

instructions and
other permanent
data.

 2001 Prentice Hall

2.26

Buses, Ports, and

Peripherals

• Information travels

between
components through
groups of wires
called buses.



Buses

connect to

storage devices in
open areas in the
box called bays.

 2001 Prentice Hall

2.27

Buses, Ports, and

Peripherals

• Busses also connect

to slots inside the

computer as well as

sockets on the

outside of the
computer called

ports

.

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2.28

Buses, Ports, and

Peripherals

• Slots and ports also allow external

devices called

peripherals

to be

added to the system (keyboard,
monitor, and mouse).



Without

peripherals

, the CPU and

memory are like a brain without a
body.