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Microsoft PowerPoint - 561 -fundamentals of computing II.ppt [Read-Only] 15.561
Information Technology Essentials
Session 2
Fundamentals of Computing II
Acknowledgments:. Copyright � 2003 Thomas Malone, Chris Dellarocas
Adapted from slides by Chris Dellarocas, U. Md..
Outline:
Fundamentals of Computing

Computer architecture
Hardware Components � CPU, Memory, I/O, Buses Understanding PC specs

Operating Systems
What is an OS?
OS Functions
� Multitasking, Virtual Memory, File Systems, Window systems
Microcomputer operating systems Bl
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The Little Man Computer
ackboard
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Input Conveyor
Ca cu ator
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Contents
100
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304
408
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521
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Output Conveyor
CD BASIC FACTS TO ASK ABOUT ANY COMPUTER LMC ANSWERS
1.
MEMORY
(A) BASIC UNIT
3 DECIMAL DIGIT NUMBER
(B) MAXIMUM SIZE 100 LOCATIONS
2.
REGISTERS
(A) HOW MANY
1
(B) NUMBERS
3 DECIMAL DIGIT NUMBER
3.
INSTRUCTIONS
(A) NUMBER
7 INSTRUCTIONS
S
M i
i
Cl
i
i
A Real Computer
CPU
Memory
0101
1101
Reg sters
001
Instruct on
Counter
ock
Keyboard
Mon tor
Mouse
Laser pr nter INTEL PENTIUM 4 ANSWERS 1. MEMORY (A) INDUSTRY
8 BINARY DIGITS (BITS) = 1 BYTE
BASIC UNIT
8 BITS 0 0 1 0 1 1 0 1 (B) BASIC UNIT
32 BITS = 4 BYTES
(C) TYPICAL SIZE MEMORY RAM: 128 MB 1GB
2. REGISTERS
(A) HOW MANY
ABOUT 50 REGISTERS
(B) NUMBERS
VARIOUS TYPES
3. INSTRUCTIONS
(A) NUMBER
ABOUT 500
SM Binary Computers

Real computers don't store and calculate with 3-digit decimal
numbers

A bit (binary digit) distinguishes between two states
TRUE and FALSE
1 and 0

Bits are easier to implement in machines
Light bulb on or off
High vs. low voltage (on wires)
Magnetized or not (computer hard disks, floppies, tapes)
Pit or no pit detected by a laser (compact discs) Interpretation of a decimal number
3 7 9 3x100 + 7x10 + 9x1 3x10
2
+ 7x10
1
+ 9x10
0
Interpretation of a binary number
1 1 0 1 1 1x2
4
+ 1x2
3
+ 0x2
2
+ 1x2
1
+ 1x2
0 1x16 + 1x8 + 0x4 + 1x2 + 1x1 27
The CPU

CPU = Central Processing Unit

Internal clock ticks very fast (e.g., 1.6 GHz = 1.6 billion ticks per
second)
activities are synchronized to start on a clock tick
some activities take more than one clock tick

Instruction execution is automatic
(tick) find memory address of next instruction
(tick) retrieve instruction from memory
(tick) decode the instruction
(tick) fetch argument from memory if necessary
(tick) execute instruction
(tick) store result in memory if necessary li
i
CPU and Memory Interaction
CPU
Address nes
Data L nes
...
...
MEMORY li
i
CPU Issues an Address
CPU
Address nes
00101010
Data L nes
...
...
MEMORY
CPU: I need the contents of memory location 50 !
li
i
Memory makes the data available
CPU
Address nes
00101010
Data L nes
01111111
...
...
MEMORY
Memory: Location 50 contains the number 127
CPU Characteristics
Family: Determines the set of instructions it understands
� Intel 80386, 80486, Pentium, Pentium II,
� Motorola: 68030, 68040
Clock Speed
� Pentium: 500 MHz 2.2 GHz
Data bus width: Size of data that can be manipulated at one time
� 80486: 32 bits, Pentium: 64 bits
Address bus width: Limits the amount of memory that can be
installed in the computer
� LMC: 3 decimal digits. Locations _______
� Pentium: 32 bits. Locations ________

� Itanium: 64 bits. Locations _________
Expressing Memory Capacity

Measured in bytes (=groups of 8 bits)

Each byte can store a binary number from 00000000 to
11111111 (255 = 2
8
-1)

More generally: n binary digits can store numbers
from 0 to 2
n
-1

Frequently used multiples:
Kilobyte (KB) = 1,024 (2
10
) bytes
Megabyte (MB) = 1,024 KB = 1,048,576 (2
20
) bytes
Gigabyte (GB) = 1,024 MB ~ 1 billion (2
30
) bytes Semiconductor Memory

RAM (Random Access Memory)
Can access any location equally fast
Loses contents without power
Two main types
� Static (SRAM): Faster, expensive
� Dynamic (DRAM): Slower, cheaper, consumes less power and
space

ROM (Read Only Memory)
Retains memory even without power
Useful to store programs executed upon system start-up (e.g. BIOS) Hard Disks and Floppies

Slower than main memory

Bits stored as magnetic field of different polarity

Magnetized surface of disk rotates under a magnetized head
(read/write mechanism)

Disk divided into tracks, each at different radius from center

Tracks are divided into sectors Hard Disk Geometry

Head moves back and forth

To read/write some data:
1. Head moves over desired track
2. System waits until desired
sector passes under head
3. Data is read/written
TRACK
CYLINDER
SECTOR
Figure by MIT OCW. CD-ROMs

Slower than hard disks

Data is encoded by burning miniature pits on a
photoreflective surface; read by laser

CDs can hold up to 650MB of data.

CD-ROM drive maximum transfer speed is expressed
in multiples of 150KB/sec
4X drive --> 600KB/sec
20X drive --> 3000KB/sec (
)
DVD Digital Video Disk

New, improved CD-ROM
smaller, denser pits
two layers of pits recorded on the same disk

DVDs can hold up to 17GB of data.
1.6 �m spacing
0.83 �m
minimum
0.4 �m
minimum
0.74 �m minimum
Figures by MIT OCW. Keychain drives

Hold 16 MB 2 GB

Attach to USB (Universal Serial Bus) port

Usually use flash memory
A special kind of ROM that can be rapidly erased and re-recorded I/O Devices

Input
Keyboard
Mouse
Hard Disk
Floppy Disk


Output
Printer
Screen
Speakers
Computer Displays

Computer screen divided into small dots (pixels)

Each pixel can be displayed in a different color

Screen resolution: Number of pixels per screen
640x480
1024x768

Color information for each pixel stored in memory, read and
converted to video signal 60 times per second
To store information for a 1024x768 screen with 256 possible colors for
each pixel we need _______ bytes /
Buses: Connecting I O to CPU

One set of wires connect all devices and CPU
Transport of information is shared (public)
Hence called a bus (public transportation)

Nearly all computers use a bus to connect CPU and
I/O Devices

Buses allow easy addition/replacement of I/O
Devices
Modern PCs come equipped with expansion slots, directly
connected to the bus
I/O Device controllers implemented as expansion cards
Examples: ISA, PCI, PCMCIA, IEEE 1394 (FireWire) li
i
A simple bus architecture
CPU
Address nes
Data L nes
BUS ...
...
...
...
...
...
...
...
...
...
...
...
MEMORY
DISK
VIDEO Cache Memory: Motivation

Cheap main memory is slower than CPU
Example: Pentium PCs � CPU 2ns (500MHZ)

� Main memory (100MHZ SDRAM) 10ns Instructions that access main memory take many more clock ticks
than those that don't

Solution:
automatically keep copies of most frequently used memory locations
in fast (but expensive) memory = cache memory (
)
A modern PC architecture
simplified
RAM
Cache
CPU
BUS Vi ll
Di
ll
Fl i
Dii
l
Sl
l
Di
deo
Contro er
VRAM
sk Contro er
oppy
Dr ve
sk
Dr ve
Faster Channe
ower Channe
sk
Cache Summary: A modern PC
Processor: Pentium (500 MHz 3.6 GHz)
Main Memory: 64 MB - 4 GB
Floppy Drive: 1.44MB (3.5-inch disks)
Hard Drive: 10 - 500GB
Graphics: 640x480 2048x1536, 256 to 16 million colors
Video Memory: 32 - 256MB Types of software

System software
Operating systems
Programming languages
Database systems

Application software
General office tasks (word processing, etc.)
Accounting
Design
Factory automation
Operating systems - Exa