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essential concepts
lesson 3
Transforming Data
into Information
This lesson includes the following sections:
• How Computers Represent Data
• How Computers Process Data
• Factors Affecting Processing Speed
• Extending the Processor's Power to Other Devices
• CPUs Used in Personal Computers
• Magnetic Storage Devices
• Optical Storage Devices
How Computers Represent Data
• Binary Numbers
• Bits and Bytes
• Text Codes
How Computers Represent Data –
Binary Numbers
•
Computer processing is performed by transistors,
switches that can be on and off.
•
All computer data is converted to a series of binary
numbers – 1 and 0. You see a word as letters; the
computer sees it as a series of 1s and 0s.
•
If a transistor is assigned a value of 1, it is on. If its
value is 0, it is off.
Ten different
symbols in
the decimal
system
Numbers above 9
use more than 1 digit
How Computers Represent Data Bits and Bytes
•
A single unit of data--called a bit--is the value assigned
to one transistor (1 or 0). A bit is the smallest unit of
data a computer can use.
•
Eight bits make up one byte. A byte can store one
alphanumeric character.
•
With one byte, the computer can represent one of 256
different symbols or characters.
.
1 01
10
1 01
01 1 01
How Computers Represent Data Text Codes
A text code is a system that uses binary numbers to
represent characters understood by humans. The
primary text code systems are:
EBCDIC -- an early text code, used mainly in older
mainframe systems.
ASCII
-- assigns each character 1 byte of data, used
in nearly all PCs.
Unicode -- assigns each character 2 bytes of data,
capable of including all the characters of
all the languages in the world.
How Computers Process Data
•
Where Processing Occurs
•
The CPU
•
Memory
How Computers Process Data Where Processing Occurs
•
Processing takes place in the central processing
unit (CPU).
•
The computer’s memory plays a crucial role in
processing data.
•
The CPU and memory are attached to the
motherboard, which connects all the computer’s
devices together.
How Computers Process Data –
The CPU
•
The CPU includes a control unit and an arithmetic logic
unit (ALU).
•
The control unit directs the flow of data through the
CPU, and to and from other devices. The control unit
stores microcode, instructions for all the tasks the CPU
can perform.
•
The actual manipulation of data takes place in the ALU.
The ALU can perform arithmetic and logic operations.
•
The ALU is connected to small memory areas -- called
registers -- that hold data and instructions while they
are processed.
How Computers Process Data –
Memory
•
Random-access memory (RAM) is volatile
(temporary). Programs and data can be written to and
erased from RAM as needed.
•
Read-only memory (ROM) is nonvolatile (permanent).
It holds instructions that run the computer when it is
first turned on.
•
The CPU accesses each location in memory by using a
unique number, called a memory address.
Factors Affecting Processing Speed
•
The size of the CPU’s registers (word size) determines
how much data the computer can process at one time.
•
The more RAM a PC has, the more program
instructions and data can be held in memory.
•
The system clock sets the pace for the CPU. Speed is
measured in Hertz (Hz), or cycles per second.
•
A bus is a path between the components of a computer,
on which data and instructions travel. The wider the
bus, the more data it can carry.
•
Cache memory is high-speed memory that holds the
most recent data and instructions that have been
loaded by the CPU.
More RAM = Better Performance!
Extending the Processor's Power to Other
Devices
•
External devices are connected to the system by
ports on the back of the computer. PCs feature
ports for devices such as a printers and mice.
•
A serial port transmits one bit at a time; a parallel
port transmits one byte at a time.
•
If the PC does not have a port for an external
device, you can install an expansion board into one
of the PC’s empty expansion slots.
Common Ports
CPUs Used in Personal Computers
•
CPU Manufactures
•
RISC and Parallel Processing
CPUs Used in Personal Computers –
CPU Manufacturers
• Intel Corp. is the world’s largest maker of
microprocessors. Intel’s 80x86 processor family
includes the 80286, 80386, 80486, and Pentium models.
• Advanced Micro Devices (AMD) has challenged Intel
in the IBM-compatible market. AMD processors
include the K6 and Athlon lines.
• Cyrix is best known as a maker of low-cost chips for
budget PCs.
• Motorola makes processors for Macintosh and
PowerPC computers. Motorola processors include the
680x0, PowerPC, G3, and G4.
CPUs Used in Personal Computers RISC Processors
•
Nearly all PC processors are called complex
instruction set computing (CISC) processors because
they contain large instruction sets.
•
Reduced instruction set computing (RISC) chips run
faster than CISC chips because they use a smaller
instruction set. RISC chips are used in mainframe
systems, minicomputers, and workstations.
•
Multiple processors can be used in a single system,
sharing processing tasks. This type of system is called
a parallel processing system.
Magnetic Storage Devices
•
How Magnetic Storage Works
•
Formatting
•
Disk Areas
•
Diskettes
•
Hard Disks
Magnetic Storage Devices How Magnetic Storage Works
•
A magnetic disk's medium contains iron particles,
which can be polarized—given a magnetic charge—in
one of two directions.
•
Each particle's direction represents a 1 (on) or 0 (off),
representing each bit of data that the CPU can
recognize.
•
A disk drive uses read/write heads containing
electromagnets to create magnetic charges on the
disk.
Write head
Medium
Random particles
(no data stored)
Current flow
(write operation)
Organized particles
(represent data)
Magnetic Storage Devices Formatting
•
Before a magnetic disk can be used, it must be
formatted—a process that maps the disk's surface and
determines how data will be stored.
•
During formatting, the drive creates circular tracks
around the disk's surface, then divides each track into
sectors.
•
The OS organizes sectors into groups, called clusters,
then tracks each file's location according to the clusters
it occupies.
Formatted Disk
Magnetic Storage Devices Disk Areas
When a disk is formatted, the OS creates four
areas on its surface:
•
Master boot record – an area of the disk containing a
small program that runs when you first start (boot) the
computer
•
File allocation table (FAT) – a log that records each
file's location and each sector's status
•
Root folder – enables the user to store data on the disk
in a logical way
•
Data area – the portion of the disk that actually holds
data
Magnetic Storage Devices Diskettes
•
Diskette drives, also known as floppy disk drives,
read and write to diskettes (called floppy disks or
floppies).
•
Diskettes are used to transfer files between
computers, as a means for distributing software, and
as a backup medium.
•
Diskettes come in two sizes: 5.25-inch and 3.5-inch.
3.5 inch
floppy
and drive
Magnetic Storage Devices Hard Disks
•
Hard disks use multiple platters, stacked on a
spindle. Each platter has two read/write heads, one
for each side.
•
Hard disks use higher-quality media and a faster
rotational speed than diskettes. As a result, a hard
disk can store many times more data than a floppy
disk.
Read/write heads
Optical Storage Devices
•
How Optical Storage Works
•
CD-ROM
•
DVD-ROM
•
Other Optical Storage Devices
Optical Storage Devices –
How Optical Storage Works
• An optical disk is a high-capacity storage medium.
An optical drive uses reflected light to read data.
• To store data, the disk's metal surface is covered with
tiny dents (pits) and flat spots (lands), which cause
light to be reflected differently.
• When an optical drive shines light into a pit, the light
cannot be reflected back. This represents a bit value
of 0 (off). A land reflects light back to its source,
representing a bit value of 1 (on).
1
0
Optical Storage Devices –
CD-ROM
•
In PCs, the most commonly used
optical storage technology is called
Compact Disk Read-Only Memory (CD-ROM).
•
A standard CD-ROM disk can store up to 650
MB of data, or about 70 minutes of audio.
Optical Storage Devices DVD-ROM
• A variation of CD-ROM is called Digital Video Disk
Read-Only Memory (DVD-ROM), and is being used
in place of CD-ROM in many newer PCs.
• Standard DVD disks store up to 9.4 GB of data—
enough to store an entire movie. Dual-layer DVD
disks can store up to 17 GB.
• DVD disks can store so much data because both sides
of the disk are used, along with sophisticated data
compression technologies.
Optical Storage Devices Other Optical Storage Devices
• A CD-Recordable (CD-R) drive lets you record your
own CDs, but data cannot be overwritten once it is
recorded to the disk.
• A CD-Rewritable (CD-RW) drive lets you record a
CD, then write new data over the already recorded
data.
• PhotoCD technology is used to store digital
photographs.
lesson 3 review
Essential concepts
•
Explain why computers use the binary number
system.
•
List the two main parts of the CPU and explain their
function.
•
List three hardware factors that affect processing
speed.
•
List four common types of storage devices.
•
Explain how data is stored on the surface of magnetic
and optical disks.