1. Hardware …and the stupidity of a computer

2. Hardware and software
In order to make a computer do something useful, we need both hardware and software
Hardware: The physical parts of the computer (monitor, keyboard, mouse and whatever is ”inside the box”)
Software: The computer programs (Word, Messenger, Counterstrike, Internet Explorer,…) we use for solving various tasks using the computer
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3. The computer way
In order to understand hardware, you need to know a little about how a computer ”thinks”
A computer does not ”think”, it calculates!
How can you make pieces of metal calculate anything useful…?
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4. On or Off A computer calculates using metal and current
A computer can only ”sense” if a current is ”On” or ”Off”
How can we employ this for doing calculations?
A transistor is used for this exact purpose
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5. Transistor A transistor is a very simple electronic device
Two wires lead into the transistor, one wire leads out
The smart part: The transistor can perform a (sort of) calculation, based on whether or not there is a current in the two input wires
A so-called logical function
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6. A smart (?) transistor So, what calculation is that?
Not so impressive, actually A B Y
Off On
Output
Input
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7. Logical, right…?
The calculation performed by the transistor is an example of a logical function
A logical funtion takes one or more input values, and pro-duces a single output value
BUT these values can only be either true or false
Also know as Boolean logic
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8. Logical functions - example
Two input values
Output A B Y
false
true
Four possible
combinations
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9. Logical functions - exampleB C Y
false
true
Three input values
Eight possible
combinations
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10. Logical functions - transistor
If we put
Off = false
On = true A B Y
false
true
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11. Zeroes and Ones
If we now exchange true with 1 (one), and false with 0 (zero), the previous table becomes: A B Y 1
This is how we usually denote ”On” and ”Off”
A numeral system using only 0 and 1 is also known as a binary numeral system
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12. The binary numeral system
Computers use the binary numeral system (aka base-2), humans (mostly) use the decimal numeral system (aka base-10)
In the context of a base-10 system, 110 means: 1x x10 + 0x1 = 110
In the context of a base-2 system, 110 means: 1x4 + 1x2 + 0x1 = 6
Alternatively:
11010 = 1x x x100 = 110
1102 = 1x22 + 1x21 + 0x20 = 6
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13. The binary numeral system
Even if binary numbers appear a bit strange, the rules for calculation are the same as for base-10
In base-10: = 12
In base-2: = 1100
Using a carry works just as before:
0 + 0 = 0
0 + 1 = 1
1 + 0 = 1
1 + 1 = 0, and 1 to carry
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14. Transistors revisited
The transistor we saw before was not able to do correct binary addition
However, if you are clever enough, you can combine transistors to implement other logical functions
Proper binary addition is just a special logical function
1+1 = ?
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15. Transistors revisited
The original transistor worked like this: A B Y 1
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16. Transistors revisited
If you combine two transistors, you can implement a different logical function A A B Y 1 B Y
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17. Transistors revisited
The combination before was not very useful, but we can of course just build more complex combinations, involving more transistors
Our goals is to be able to do binary addition
Binary addition is ”just” a special logical function, taking three input values and producing two output values
Can be considered to be two separate logical functions
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18. Binary addition A B
Carry in Y
Carry out 1
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19. This should do the trick…
Some clever person found out that the below combination implements proper binary addition
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20. The first building block
We have now found a way to do proper addition, using metal and current
Implementing the other arithmetic operations is then not particularly complicated
This actually forms the foundation for the first electronic computers
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21. ENIAC Built around 1945 Weighs about 30 tons Based on vacuum tubes
Ca transistors
Used for calculating projectile trajectories
Was only operational about half of the time…
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22. 60 years later
Today we do not use individual transistors. A chip contains a (large) number of transistors
Most advanced chips contain a few billion transistors – within an area of perhaps 1 cm2
What if car technology had progressed at the same rate:
Price: 1 $
Gas consumption: km/l
Max speed: km/h
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23. Moore’s law
”Within two years, the number of transistors on a chip will double”
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24. From 0 and 1 to Counterstrike
Even if we can now make metal and current do calcu-lations, there is still a very long way from 0’s and 1’s to Counterstrike…
A computer can handle vast amounts of data, at vast speeds
How fast?
How much data?
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25. Bits and bytes
For a computer, the basic unit for data is an entity which is either 0 or 1
This entity is called a bit
A computer performs operations on bits.
A more practical unit is a sequence of 8 bits; this is known as a byte.
Why 8 bits? Why not 7 or 9? Tradition…
We can for instance define a character set using 8 bits
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26. Bits and bytes How many distinct bytes are there?
One byte is 8 bits, each bit is either 0 or 1
Combinations: 2x2x2x2x2x2x2x2 = 256 (28)
Each combination can now be interpreted as a specific symbol (letter, number, etc), for instance the letter ”H”
With 256 combinations, we have enough combinations for capital letters, small letters, numbers, etc..
Example: ASCII codes
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27. ACSII codes
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28. Amounts of data
Amounts of data are usually measured in bytes (each byte being 8 bits)
For a computer, all kinds of data are just sequences of bits
It requires a program – written by humans – to interpret a bit sequence as e.g. music, video, a Word docu-ment, and so on
How many bytes does each type of data require?
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29. Size of some data types Plain text (no pictures) Music (mp3 format)
Video
(DVD quality)
Kilo-byte
Half a page
--- --
Mega-byte
500-page novel
One minute
One second
Giga-byte
Large book-shelf
16 hours
20 minutes
Tera-byte
Large library
Two years
Two weeks
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30. Speed of calculation
When a computer calculates, it processes many sequences of bits simultaneously
All calculation units must be ”syn-cronized” for this to work properly
A ”conductor” manages when the calculation units should calculate
The speed of the conductor defines the speed of the computer
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31. Speed of calculation
How many ”beats per second” (hertz) can the conductor manage?
Old computer (ENIAC); about beats per second (10 kiloHertz)
Modern PC; about beats per second (3 GigaHertz)
Also known as clock rate
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32. 3.000.000.000 Hertz Three billion beats per second is quite fast…
For every beat, light only travels 10 centimeters
The physical size of the chip begins to matter
Unfortunately, energy consump-tion rises with the clock rate, at a quadratic rate
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33. CPU Where are calculations actually performed?
Calculations are done in a unit called the CPU (Central Processing Unit)
This unit is basically just one large chip, which looks fairly uninteresting…
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34. The CPU and Primary Storage
The job of the CPU is to perform calculations on streams of bits, but who provides these bits?
Somebody has to feed bits to the CPU, and ”consume” the results produced by the CPU
For this task, the computer uses the Primary Storage
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35. Primary Storage A calculation involves the below steps
Input data is moved from primary storage to the CPU
The CPU performs the calculation
The result is moved from the CPU to primary storage
The primary storage is thus just a ”container” for a certain amount of data
The primary storage is ”passive”; no kind of data processing is performed here
Primary storage is usually of the type RAM (Random Access Memory)
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36. Primary Storage What is primary storage physically?
Just some chips, which contains a certain amount of data
A modern PC will typically have 2-8 Gigabytes of primary storage
What could the data represent? For instance data from an mp3-file, for which the CPU must perform some calculation to transform it into music
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37. Primary vs. Secondary
Primary storage (RAM) has a large advantage: transfer of data between the CPU and RAM is quite fast (several Gigabytes pr. second)
Fast – but compared to what?
There are however also several drawbacks:
RAM is expensive (compared to what?)
When power is cut, all data in the primary storage will be lost
We thus also need secondary storage
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38. Secondary storage
Who provides data to the primary storage? That data is provided by secondary storage
What is secondary storage? In principle the same as primary storage – a passive container for data - but
Is much cheaper than RAM (per byte)
Data is preserved when power is turned off
Presently, the most common form of secondary storage in a PC is a hard drive
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39. Quite hard…(old school)
A (traditional) hard drive con-tains a number of magnetic platters, on which individual bits are stored by magnetising a specific area of the platter
A modern hard drive contains 500-2,000 Giga-bytes of data
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40. Quite hard…(new school)
A SSD (Solid-State Drive) hard drive contains a number of memory chips, on which individual bits are stored in transistors (but retained when power is turned off)
A modern SSD contains Giga-bytes of data
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41. Hard drive vs. RAM Hard drive (Traditional) (SSD) RAM
Typical amount in PC GB GB
2-8 GB
Price pr. Gigabyte
≈ 0,5 kr.
≈ 10 kr.
≈ 100 kr.
Data transfer speed
0,1-0,3 GB/sek
0,5-1 GB/sek
4-8 GB/sek
Preserves data without power
Yes No
Technology
Mechanical
Electronic
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42. Harddisk vs. RAM In other words: RAM: Hard drive:
Very fast and stable, BUT
Expensive, does not preserve data without power
Hard drive:
Cheap, large capacity and preser-ves data without power, BUT
Rather slow, mechanical technology (except SSD)
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43. Other types of secondary storage
USB-key
CD, DVD and Blu-ray
Floppy disks
Online
Capacity
(Gigabytes)
2-256
0,7-30
0,0015 (!) ??
Price
(kr pr. GB)
Ca. 10
Ca. 1
>100
Speed
(MB pr. sek)
10-100 25
< 1
Depends on connection
Technology
Electronic
Optical / Mechanical
Magnetic / Mechanical
Internet
Note
Same tech as SSD
Stagnant
Almost extinct
On the rise
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44. Motherboard
A PC contains a board, on which the central components of the PC are mounted – this board is usually denoted the motherboard
The motherboard will (at least) contain
CPU
RAM (primary storage)
Auxiliary components
Sockets/slots for adding ”other components”
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45. Other components Examples of ”other components” are:
Graphics card
Sound card
Network card
TV card
In some PCs, these components are found directly on the motherboard, on others they are found as extra components, inserted into slots on the motherboard
Why…?
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46. Other components
Even though a modern CPU is very fast, it may benefit from being relieved from certain tasks
Graphics card
Specially designed for effective graphics calculations
Takes computational load off CPU
May increase graphical performance by a factor 100
Typical application: GAMES!
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49. Data exchange by bus
All these units and components need to exchange data in order to do their job
How do they do that?
Data exchange is done using so-called data buses
A data bus transports data between two units
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50. Data exchange by bus A data bus sends data:
A number of times pr. second
A certain amount of data each time
Example: a 32-bit bus running at 100 Mhz
Carries 32 bit (4 bytes) each time
Sends 100 million times pr. second
A PC contains a number of buses running at different speeds
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51. Countryside bus
A bus is also used for exchanging data with additional components, like a graphics card
Types of buses for extra components:
PCI (Peripheral Component Interconnect) – those slots in which additional components (such as a graphics card) can be inserted
USB (Universal Serial Bus) – used by many external devices such as printers, USB memory keys, etc..
Fortunately, buses follow a standard
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52. External devices
Devices which enable communication between humans and computers
Typical external devices
Keyboard and mouse
Monitor
Speakers / headset
Printer
But also
Digital camera, phone, USB-key, …
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