Transcript Document 7708142

COMMON COMPUTER HARDWARE
The Monitor is the display screen, similar to a television screen.
The Keyboard is what you type on, similar to a typewriter
The Mouse is the small hand held device that attaches to the computer. It may
have two or three buttons. The mouse is used to move the cursor (pointer) on the
computer screen.
The Computer, tower, or case is the heart of the system. This is a box
that contains all the parts that make the computer work. It can be
identified by the fact that it does not seem to do anything. It also has
slots to put computer disks in.
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Our PCs are data processors
The PC's function is simple: to process data, and the processing is done electronically
inside the CPU and between the other components.
That sounds simple, but what is data, and how is it processed electronically in a PC?
ANALOG DATA :
the type of data we use in our everyday life :
photos, sound, letters, numbers ….
these can vary in type – unusable for PCs
DIGITAL DATA :
PC is an electrical unit
therefore can only deal with simple electrical data:
electric switches : ON / OFF
OFF
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ON
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The PC is filled with these switches (computers first had vacuum tubes – computers
today have transistors).
DATA PROCESSING = understanding these 1’s and 0’s …
Each 0 or 1 is called a bit.
Bit is an abbreviation of the expression BInary digiT.
It is called binary, since it is derived from the binary number system:
0
1 bit
1
1 bit
0110
4 bits
01101011
8 bits : 1 Byte
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How does the computer process this data?
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DATA PROCESSING
The most basic data processing is word processing.
When we do word processing, we work at a keyboard similar to a typewriter.
There are 101 keys, where we find the entire alphabet A, B, C, etc. We also find the
digits from 0 to 9 and all the other characters we need:,.-;():_?!"#*%&etc..
All these characters must be digitized = They must be expressed in 0s and 1s.
Bits are organized in groups of 8. A group of 8 bits is called a byte.
Why 8???
2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 256 different bytes are possible !
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Character
Bit pattern
Byte
number
Character
Bit pattern
Byte
number
A
01000001
65
¼
10111100
188
B
01000010
66
.
00101110
46
C
01000011
67
:
00111010
58
a
01100001
97
$
00100100
36
b
01100010
98
\
01011100
92
o
01101111
111
~
01111110
126
p
01110000
112
1
00110001
49
q
01110001
113
2
00110010
50
r
01110010
114
9
00111001
57
x
01111000
120
©
10101001
169
y
01111001
121
>
00111110
62
z
01111010
122
‰
10001001
137
ASCII means American Standard Code for Information Interchange.
(originally 7-bit)
ANSI is the 8-bit encoding system developed by the American National
Standards Institute.
It is an industry standard, which assigns letters, numbers, and other characters within
the 256 slots available in the 8 bit code.
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The ASCII table is divided in 3 sections:
1) Non printable system codes between 0 and 31.
2) "Lower ASCII" between 32 and 127. This part of the table originates from older,
American systems, which worked on 7 bit character tables. Foreign letters, like Ø
and Ü were not available then.
3) "Higher ASCII" between 128 and 255. This part is programmable, in that you can
exchange characters, based on which language you want to write in. Foreign letters
are placed in this part.
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Number systems

Decimal


385 = 3*10² + 8*10¹ + 5*10º
Hexadecimal 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F



0,1,2,3,4,5,6,7,8,9
3AF = 3*16² + 10*16¹ + 15*16º
3AF = 768 + 160 + 15 = 943 in decimal
Binary


0,1
1111 = 1*2³ +1*2² +1*2¹ +1*2º = 15 (dec)
10011010= 1*128+0*64+0*32+1*16+1*8+0*4+1*2+0*1

=128+16+8+2 = 154
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Conversion to Binary: Integer

Method: divide the number and each successive
quotient by 2, noting the remainders.

Decimal
Divisions
Quotients
Binary
Remainders
137/2
68/2
34/2
17/2
8/2
4/2
2/2
1/2
68
34
17
8
4
2
1
0
1
0
0
1
0
0
0
1
Result
(10001001)2
=
least significant bit
most significant bit
(137)10
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Conversion to Binary: Floating Point

Method: Multiply the number and each successive
fractional by 2, noting the integral part of product.
Dec
Multiplications
0.78125 * 2 =
0.5625 * 2 =
0.125 *2 =
0.25 * 2 =
0.5 * 2 =
Result
(0.11001)2
=
Product
Binary
Integral part
1.56250
1.1250
0.250
0.50
1.0
1
1
0
0
1
most significant bit
least significant bit
(0.78125)10
Note: Stop when 1.0 or repeating itself reached after substraction of integral part. (try 0.6)
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Example

Floating point numbers
1101.1101
2-4 = 0.0625
0*2-3 = 0*0.125 = 0
2-2 = 0.25
2-1 = 0.5
0.8125
23
22
21
20
(8+4+0+1)=13
13.8125
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Example
Remainders
Integral part
13.6875 conversion into binary form
13/2
0.685
6/2
1
x2
3/2
0
1.3750
1
1
x2
0.7500
x2
1.5000
x2
1.0000
Result: 101.1011

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Binary operations

Addition
(71)10 =
+ (36)10 =
(107)10 =
1
1000111
0100100
1101011
Carries (Onhand)
Addend
Augend
1*2º = 1
1*2¹ = 2
1*2³ = 8
1*25 = 32
1*26 = 64
107
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Binary operations

Subtraction
02
02
(13)10
- (7)10
(6)10
=
=
=
Borrowings
1101
0111
0110
Minuend
Subtrahend
Difference
1*2¹ = 2
1*2² = 4
6
Example:
00110 01
1100101001
- 110110110
101110011
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Binary operations

Multiplication
(10)10 =
x (5)10 =
(50)10 =
+
1010
0101
1010
0000
1010
0000
0110010
= 32+16+2 = 50
multiplier
product
Note: Addition of each two sub lines are prefferred to prevent potential misstakes.
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Binary operations

Division
1010001/11
2
110010 / 1010
- 1010
00101
1010
- 001010
- 1010
- 0000
11011
= 101
quotient
11) 1010001
11
100
11
100
11
11
11
00
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Binary operations

Subtraction by “addition with complement”
B -A = B+Ā9 –10n +1
878
- 539
339
where n: number’s power
correction
complement
878
+ 460
1338
- 1000
(103)
(Truncate)
338
+
1
339
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Binary operations

Subtraction by “addition with complement”
Complement : 2-1 = 1
(13)
1101
1101
- (7)
0111
1000
(6)
0110
10101
+
1
0110
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(Truncate/Shift left)
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There are 2 fundamental types of data:
•Program code, which is data, that allows the PC to function.
•User data, like text, graphics, sound.
The fact is, that the CPU must have instructions to function.
An instruction is a string of data, of 0s and 1s. The CPU is designed to
recognize these instructions, which arrive together with the user input data to
be processed.
The program code is thus a collection of instructions, which are executed one
by one, when the program runs. Each time you click the mouse, or hit a key on
the keyboard, instructions are sent from your software (program) to the CPU,
telling it what to do next.
User data are those data, which tells the software how to respond. The letters,
illustrations, home pages, etc., which you and I produce, are created with
appropriate software.
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Both program code and user data are saved as files on the hard disk.
Often, you can recognize the type of file by its suffix. Here are some
examples:
Content
File name
Program code
START.EXE, WIN.COM, HELP.DLL, VMM32.VXD
User data
LETTER.DOC, HOUSE.BMP, INDEX.HTM
BUT HOW DOES THE COMPUTER RECOGNIZE THESE DATA,
OR WHAT TO DO WITH THEM ???
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A drive is the name for several types of storage media.
Common to drive medium is:
A file system can be assigned to them.
They are recognized by the operating system and they are assigned a drive letter.
During start up, drives are typically recognized by the PC system software (ROM BIOS
+ operating system).
Thus, the PC knows which drives are installed.
At the end of this configuration, the appropriate drive letter is identified with each
drive.
If a drive is not "seen" during start up, it will not be accessible to the operating
system.
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Storage media
Drive letter
Floppy disks
A: B:
Hard disk
C: D: E:
CDROM/DVD
F:
MO drive
G:
Network drive
M:
RAM disk
O:
Data on any drive are digitized. That means that they are expressed as myriads of
0s and 1s. However, the storage of these bits is done in any of three principles:
The physical drive principle
Disk types
Magnetic
Floppy disks
Hard disk
Syquest disks
Zip drive
LS-120 disks
Optic
CD-ROM
DVD
Magneto optic
High end drives
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HARD DISKS
Invented in the 1950s, they were initially capable of storing about 1 Megabyte of data
Name
Abbr.
Size
Kilo
K
2^10 = 1,024
Mega
M
2^20 = 1,048,576
Giga
G
2^30 = 1,073,741,824
Tera
T
2^40 = 1,099,511,627,776
Peta
P
2^50 = 1,125,899,906,842,624
Exa
E
2^60 = 1,152,921,504,606,846,976
Zetta
Z
2^70 = 1,180,591,620,717,411,303,424
Yotta
Y
2^80 = 1,208,925,819,614,629,174,706,176
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HARD DISKS
At the simplest level, a hard disk is not that different from a cassette tape. Both
hard disks and cassette tapes use the same magnetic recording techniques.
Hard disks and cassette tapes also share the major benefits of magnetic storage -the magnetic medium can be easily erased and rewritten, and it will "remember"
the magnetic flux patterns stored onto the medium for many years.
IBM introduced the first hard disk in 1957, when
data usually was stored on tapes. The first 305
RAMAC (Random Access Method of Accounting and
Control) consisted of 50 platters, 24 inch diameter,
with a total capacity of 5 MB, a huge storage
medium for its time. It cost $35,000 annually in
leasing fees (IBM would not sell it outright) and was
twice the size of a refrigerator.
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There are two ways to measure the performance of a hard disk:
Data rate - The data rate is the number of bytes per second that the drive can
deliver to the CPU. Rates between 5 and 40 megabytes per second are common.
Seek time - The seek time is the amount of time between when the CPU
requests a file and when the first byte of the file is sent to the CPU. Times
between 10 and 20 milliseconds are common.
The other important parameter is the capacity of the drive, which is the
number of bytes it can hold.
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INSIDE A HARD DISK
OPENING A HARD DISK RUINS IT, so this is not
something to try at home unless you have a defunctional
drive.
It is a sealed aluminum box with controller
electronics attached to one side.
The electronics control the read/write
mechanism and the motor that spins the
platters.
The electronics also assemble the magnetic
domains on the drive into bytes (reading) and
turn bytes into magnetic domains (writing).
The electronics are all contained on a small
board that detaches from the rest of the drive.
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The platters, which typically spin at 3,600 or
7,200 rpm when the drive is operating. These
platters are manufactured to amazing tolerances
and are mirror-smooth…
The arm that holds the read/write heads is
controlled by the mechanism in the upper-left
corner, and is able to move the heads from the hub
to the edge of the drive.
The arm on a typical hard-disk drive can move
from hub to edge and back up to 50 times per
second.
In order to increase the amount of information the
drive can store, most hard disks have multiple
platters.
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Data is stored on the surface of a platter in
sectors and tracks.
Tracks are concentric circles, and sectors are
pie-shaped wedges on a track.
4 sides
300 tracks/side
40 sectors/track
512 bytes/sector
5,400 rpm rotational speed
1 ms track-to-track step time
The process of low-level formatting a drive establishes the tracks and sectors on
the platter. The starting and ending points of each sector are written onto the platter.
This process prepares the drive to hold blocks of bytes.
High-level formatting then writes the file-storage structures, like the file-allocation
table, into the sectors. This process prepares the drive to hold files.
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FLOPPY DISK AND FLOPPY DISK DRIVE
The floppy disk drive (FDD) was invented at IBM by Alan Shugart in 1967.
The first floppy drives used an 8-inch disk that evolved into the 5.25-inch disk that was
used on the first IBM Personal Computer in August 1981.
The 5.25-inch disk held 360 kilobytes compared to the 1.44 megabyte capacity of
today's 3.5-inch diskette.
The 5.25-inch disks were dubbed "floppy" because the diskette packaging was a very
flexible plastic envelope, unlike the rigid case used to hold today's 3.5-inch diskettes.
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Floppy Disk Drive Terminology
Floppy disk - Also called diskette. The common size is 3.5 inches.
Floppy disk drive - The electromechanical device that reads and
writes floppy disks.
Track - Concentric ring of data on a side of a disk.
Sector - A subset of a track, similar to wedge or a slice of pie.
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The major parts of a FDD include:
Read/Write Heads: Located on both sides of a diskette, they move together on the
same assembly. The heads are not directly opposite each other in an effort to prevent
interaction between write operations on each of the two media surfaces. The same head
is used for reading and writing, while a second, wider head is used for erasing a track
just prior to it being written. This allows the data to be written on a wider "clean slate,"
without interfering with the analog data on an adjacent track.
Drive Motor: A very small spindle motor engages the metal hub at the center of the
diskette, spinning it at either 300 or 360 rotations per minute (RPM).
Stepper Motor: This motor makes a precise number of stepped revolutions to move the
read/write head assembly to the proper track position. The read/write head assembly is
fastened to the stepper motor shaft.
Mechanical Frame: A system of levers that opens the little protective window on the
diskette to allow the read/write heads to touch the dual-sided diskette media. An external
button allows the diskette to be ejected, at which point the spring-loaded protective
window on the diskette closes.
Circuit Board: Contains all of the electronics to handle the data read from or written to
the diskette. It also controls the stepper-motor control circuits used to move the
read/write heads to each track, as well as the movement of the read/write heads toward
the diskette surface.
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WRITING DATA TO A FLOPPY DISK
The computer program passes an instruction to the computer hardware to write a data file on a
floppy disk.
The computer hardware and the floppy-disk-drive controller start the motor in the diskette drive to
spin the floppy disk.
The stepper motor rotates a worm-gear shaft in minute increments that match the spacing
between tracks.
The time it takes to get to the correct track is called "access time."
The read/write heads stop at the track. The read head checks the prewritten address on the
formatted diskette to be sure it is using the correct side of the diskette and is at the proper track.
Before the data from the program is written to the diskette, an erase coil (on the same read/write
head assembly) is energized to "clear" a wide, "clean slate" sector prior to writing the sector data
with the write head.
The erased sector is wider than the written sector -- this way, no signals from sectors in adjacent
tracks will interfere with the sector in the track being written.
The energized write head puts data on the diskette by magnetizing minute, iron, bar-magnet
particles embedded in the diskette surface.
The diskette stops spinning. The floppy disk drive waits for the next command.
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OPTICAL STORAGE MEDIA
Drive type
Name
The drive can
CD-ROM
Compact Disk Read Only
Memory
Read CD-ROM and CD-R
CD-ROM
multiread
--''--
Read CD-ROM, CD-R and CD-E
CD-R
Compact Disk Recordable
Read CD-ROM and CD-R. Write once on
special disks named CD R
CD-RW
Compact Disk ReWritable
Read CD-ROMs and CD-R. Write and re-write
on special disks (CD-RW).
DVD RAM
Digital Versatile Disk Random
Access Memory
Reads all CD formats. Reads DVD ROM.
Reads and writes DVD disks
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The CD-ROM can be compared to a floppy drive, because the disks are removable. It
can also be compared with a hard drive, because of similar data storage capacity.
Actually, a CD-ROM disk can hold up to 680 MB of data. This equals the capacity of 470
floppy disks. However, the CD-ROM is neither a floppy nor a hard disk!
In the optic readable CD-ROM, the data storage consists of millions of indentations burnt into
the lacquer coated, light reflecting silver surface. The burnt dents reflect less light than the
shiny surface. A weak laser beam is sent to the disk through a two-way mirror and the sensor
registers the difference in light reflection from the burnt and shiny areas as zeros and ones.
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The CD-ROM holds one long track, running from the
center outwards
A 5 km long spiral track holds up to 650 MB data in
about 5.5 billion dots (each is one bit).
The CD-ROM disk has to read in random pattern.
The read head must jump frequently to different parts of the disk. It causes pauses in
the read function. That is a disadvantage of the CD-ROM media. Also the faster drives
can be rather noisy.
CD-ROM type
Data transfer rate
Revolutions per minute outermost - innermost
track
1X
150 KB/sec
200 - 530
2X
300 KB/sec
400-1060
4X
600 KB/sec
800 - 2,120
8X
1.2 MB/sec
1,600 - 4,240
40X CAV
2.6 - 6 MB/sec
8,900 (constant)
40X40 multibeam
6 MB/sec
1,400 (constant)
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CD-R
To make your own CD-ROMs, you use a drive (a
“burner”), which can write on special CD-ROM disks.
These disks have a temperature sensing layer, which can
be changed by writing. You can only write on any given
part of these disks once.
This CD-R disk is also called a WORM disk (Write Once
Read Many).
CD-RW
The CD-ReWritable (CD-RW) is another type of CD, where you can write multiple
times on the same disk surface.
However, not all CD drives can read these CDs. To work with CD-RW you need special
software (eg Adaptecs).
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MEMORY STORAGE
The capacities of RAM, cache and other memories are desribed in terms of the
number of bytes they can store.
RAM :
Random Access Memory
ROM :
Read-Only Memory
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Sequential file
1
2
3
4
5
6
(like a magnetic tape)
Direct Access / Random Access File
(need addressing scheme)
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