Transcript computersystems

Computer Systems
TexPREP Summer Camp
Computer Science
Computer System
Hardware
Computer System
All those parts of a computer that you
can see and touch.
Software
Programs (set of instructions) and
data.
www.coolnerds.com/Newbies/Hardware/hardware.htm
Hardware
Computer
http://www.antonine-education.co.uk/ict_as/ict_module_2/topic_8/computer_architecture.htm
Hardware
The two most important components of a
computer are:
• CPU: Central Processing Unit
• Memory: typically RAM (Random Access
Memory)
They are connected by the system bus and are
located on the motherboard.
CPU
The CPU is the “brain” of the computer.
• It gets an instruction from main memory and then executes
it.
• If the instruction needs some data, it gets the data from
main memory in order to process it.
• After executing the instruction, if there is a result that
needs to be saved, it stores the result on main memory.
These steps are repeated for each instruction in the program.
The speed of the processor is expressed in Gigahertz (GHz).
Memory
There are different types of memory in a computer system.
• Main memory (RAM): where programs and data must be
loaded in order to be processed.
• ROM: where the boot (startup) program is stored.
• Cache: very high speed memory used to improve the
performance of the system.
The amount of memory is typically expressed in Megabytes (MB),
Gigabytes (GB), or Terabytes (TB).
RAM and Cache are volatile, that is, they lose their content when the power is
turned off. ROM is not volatile.
Their access time is in the order of nanoseconds (0.000000001 seconds)
System Clock
The components of the computer must interact
in a synchronized way.
A system clock is used to control the timing of all
computer operations.
It generates regular “ticks” (electronic pulses)
that set the operating pace of the
components.
Its speed is expressed in Megahertz (MHz) or
Gigahertz (GHz).
Peripheral devices
• Storage devices: used to store data and programs
permanently (non volatile). For example: hard drive,
flash drive, cd drive, etc.
• Input devices: used to enter data and instructions
(programs, commands, etc.) into the computer. For
example: keyboard, mouse, microphone, scanner,
etc.
• Output devices: used to get information from the
computer. For example: monitor, printer, speakers,
etc.
Storage devices
The three main technologies are:
• Magnetic: used on hard disks, tape, etc.
• Optical: used on CDs (ROM, R, RW), DVDs (R, RW,
RAM), etc.
• Solid state: used on flash drives, memory cards,
etc.
Hard drive
http://www.pctechguide.com/31HardDisk_Construction.htm
Optical Discs
disc label
lens
pit
lens
land
Step 3.
0
prism
Step 1.
Laser diode
shines a light
beam toward
disc.
Step 2.
If light strikes
a pit, it scatters.
If light strikes a
land, it is
light- reflected back
sensing toward diode.
1
prism
lightsensing
diode
diode
laser
diode
laser
diode
Discovering Computers 2006, Course Technology, p. 367 Fig. 7-20
Reflected light is
deflected to a
light-sensing diode,
which sends digital
signals of 1 to
computer. Absence
of reflected light is
read as digital
signal of 0.
Adapter Cards
Also known as expansion boards, are used to
increase the capabilities of a computer.
They must be inserted in expansion slots and
their respective device drivers installed before
they can be accessed by the system.
There are different technologies: PCI, AGP, etc.
Motherboard
http://www.washington.edu/lst/help/computing_fundamentals/troubleshootingxp/hardware
Adapter Cards examples
• video adapters
• graphics accelerators
• sound cards
• accelerator boards
• NIC - network interface card
Graphics Adapter Card
http://salestores.com/stores/images/images_747/P65MDDE128LPUF.jpg
Units of measurement
KILO: 1,000 or 103
MEGA: 1,000,000 or 106
GIGA: 1,000,000,000 or 109
TERA: 1,000,000,000,000 or 1012
Digital Representation
Inside the computer…
Everything is discrete (digital), not
continuous (analog) – i.e, it must be
represented using a discrete (number)
value
Problem: How do we put the analog
world “inside” the digital computer?
Solution: Devise ways to represent
real-world, analog data in digital forms
What do computers work with
internally?
Computers have storage units called binary digits or bits
The computer operates with voltage through what
amounts to microscopic switches that are either “On” (1)
or “Off” (0)
Low Voltage = 0
High Voltage = 1
all bits have value 0 or 1
Representing Numbers
Binary number system
Representing Characters
ASCII (American Standard Code for Information
Interchange) and Unicode