Lecture 2 (1)

Computer
general purpose device that can be programmed to carry out a set of arithmetic or logical operations
(Examples: cameras, phones)
Two main parts of computer:
Hardware refers to the physical parts of the computer
Example: piano is a hardware
Software refers to the code that runs on the computer
Example: the music is the software

"Computer" word's history
The term "computer", in use from the early 17th century , meant "one who computes": a person performing mathematical calculations, before electronic computers became commercially available.
"The human computer is supposed to be following fixed rules; he has no authority to deviate from them in any detail."

US Census 1890
US Census 1880 has taken 8 years to summarize data.
Hollerith invented "Tabulating machine" electromechanical machine that was made for summarization of census

Mechanical relay
Light turns on if coil was turned on

Before transistors
Vacuum tubes:

Transistors
Transistor is a “solid state” device, meaning it has no moving parts
works as a sort of amplifying valve for a flow of electrons
It is a basic building block used to construct more complex electronic components
Nowadays transistors are made of silicon
silicone (rubber) and silicon (chips, кремний) are different

When B is ON current goes through C to E
When B is OFF current doesn't go through C to E

Water analogy
We can apply water tube analogy to transistors

What we can do with transistors?

AND gate
When A is OFF and B is OFF current can’t pass A gate, Out is OFF When A is OFF and B is ON current can’t pass A gate, Out is OFF
When A is ON and B is OFF current pass A gate, but can’t pass B gate, Out is OFF
When A is ON and B is ON current pass A gate, and B gate, Out is ON

AND logic table
Instead of OFF we can use FALSE
Instead of ON we can use TRUE

Schemes that perform logical operations
OR
NAND
NOR

Basic Logic gates
AND
OR
XOR
NOT

Basic Logic gates (2)
NAND
NOR
XNOR

How to add two numbers by logic gates
Let's create simplest ever calculator It adds two binary numbers
So let's find what should it output, on specific inputs Output is XOR gates, and Carry is AND gate

Binary adder (half adder)
+ 1
1
1 0

Scheme for adding two 4-bit numbers, input switches are A3, A2, A1, A0 and B3, B2, B1, B0, sum is outputted into S3, S2, S1, S0

Full adder

What does this scheme do?

Memory using logic gates
Flip-flops are used to save information, when S is 1, Q is equal to R, when S

Chips
Computer contains millions of chips
Chip- fingernail sized silicon
Chip can contain billions of transistors
Chips in plastic package with metal pins
CPU chips , memory chips, flash chips

Whole picture
Transistors are switches
Logic gates are created from Transistors
Logical and arithmetical units are created from Logic gates Chips consist of many logical and arithmetical units

Moore’s law
Transistors get smaller about every 18-24 months
Can fit twice as many per chip
It is observation, not law
In effect, transistors/computers get cheaper (powerful)
Why computers are now in cars, thermostats
$50 MP3 player bigger every couple years: 2GB, 4GB, 8GB
Exponential - 10 doublings, about 1000 x
Moore's law ... computers cheap, everywhere

Computer hardware
There are 3 major parts that make up a computer: CPU, RAM, Persistent Storage

CPU
CPU- Central Processing Unit
CPU is big chip with many different logical and arithmetical units
The brains of computer
Performs simple operations
e.g. Add two numbers, copies data from one memory to other
Run button… code “runs” on the CPU

RAM - (Random Access Memory)
RAM- Memory, Random Access Memory
It is called Random Access, because any needed memory can be accessed immediately, whereas in magnetic hard disk, it takes time to rotate disc to specified place Temporary, working storage bytes
e.g. typing text in MS Word before saving document, text is stored in RAM
e.g. while playing game, the units location and life is stored in RAM RAM is “volatile”, not “persistent”,..gone when power goes out

What does RAM do?
"In simple terms, RAM is to Disk Memory as Pockets is to your bag. When you are going about your usual day(processing) you keep things needed frequently to you in your pocket and the remaining stuff in your bag. The reason you do this is you can access your pockets with less time compared to opening your bag and getting things out of it.
The computer does the same thing with memory. It has everything it needs in the Disk Space
but accessing that memory takes a lot of time. So it keeps the most frequently used data(currently and predictably) in the RAM which is constructed using a transistor and a capacitor connected in a matrix of word and bit lines, as it is faster to access compared to the drive which is a spinning physical disk."
Quora (Akshay Sharma)

Persistent Storage: Hard Drive, Flash Drive
Hard Drive
Stores bytes as a magnetic pattern on a spinning disk
Fragrant
Heavy
Flash Drive
Stores bytes as electrons in a chip
No moving parts
More expensive
Uses less power
e.g. usb key, SD card in camera, flash chips built into a phone or tablet

Persistent Storage, Hard drive, Flash drive
Nowadays most laptops use hard drive, the only reason for using hard drive is they are cheap.
But flash drive’s cost is got cheap, from year to year, and it is expected in next 5 years that most laptop will contain flash drives instead of hard drives.

Whole picture
Any program makes arithmetic and logical operations with some data. Data that needs to be saved for long time is stored in hard drive
Data that is operated by CPU and is used very frequently is stored RAM

Measurements
Hertz - operations per second
Hz is abbreviation of Hertz
CPU’s performance is measured in hertzes
Bit - is measurement of memory. Bit’s value can be 1 or 0.
Byte consists of 8 bits
Hard drive’s, flash drive’s and RAM’s are measured by bits
Kilo - 10^3
Mega - 10^6
Giga - 10^9
Tera - 10^12
Peta - 10^15

Ǫuestion???
You have written code for strategy game. Any warrior has 10 different values presenting his skills, abilities, life and etc. All of them are saved in int typed variable. Each int variable takes 12 bytes in memory. If you have created an army of 100000 warriors.
What is the minimum size of necessary RAM memory?
You type some document of size 10000 symbols. Each symbol takes 1 byte of memory.
What is the minimum size of necessary hard drive’s memory?

Arduino
Arduino is programmable microcontroller
You can program it
It receives input signals processes it and output signals
You can design your own gadgets
Lots of compatible devices and sensors
Costs ~20$

Arduino: what can we do?
http://www.makeuseof.com/tag/arduino-technology-explained/ :
it’s like a little computer you can program to do things, and it interacts with the world through electronic sensors, lights, and motors. In essence, it makes some truly hardcore electronics projects accessible to anyone – so artists and creative types can concentrate on making their ideas a reality. It’s the ultimate tinkering tool

Evolution of computers
1940 - 1945: computers used mostly for deciphering messages
Took place of 100 square meters or more
1946 ENIAC computer has been completed
Speed: 5,000 operations per second (5 kHz)
Input/output: cards, lights, switches, plugs
Floor space: 1000 square feet (about 100 square meters)
1951 UNIVAC. First commercial computer
Speed: 1,905 operations per second (2 kHz)
Input/output: magnetic tape, unityper, printer
Memory: 1,000 12-digit words. (1.5 KB) (delay lines, magnetic tape)
Floor space: 26 cubic meters
Cost: F.O.B. factory $750,000 plus $185,000 for a high speed printer

Evolution of computers (2)
1956 first computer build with transistors
1950s - 1970s beginning of commercial computers’ era
computers were bought by companies, universities and army
They become small and more productive
1977 first personal computers were sold. Whose main characteristics were:
Price: 600$
4 kilobytes of memory
cassette storage
1984 apple’s Macintosh computer (http://www.youtube.com/watch?v=2B-XwPjn9YY)
Price: 2500$
Graphical interface
Mouse

Evolution of computers (3)
1990s - 2000s: Era of personal computers
2000s - 2008s:Laptops, get smaller and cheaper
2004 - now: Phones got smarter
2008 - now: Tablets get more popular
in 2012 tablets and smartphones were sold more than personal computers

Evolution of input devices
switches
punched cards (перфокарты)
keyboard
mouse
screen

Punch card
https://www.youtube.com/watch?v=KG2M4ttzBnY

Evolution of output devices
Punched cards
Printer
Monitor

Evolution of storage devices
Magnetic tapes
Magnetic disks
1961 IBM’s magnetic disk
Capacity 28 million characters (28 MB)
cost: $2100 per month, or purchased for $115000
1994: Floppy disks
size: 1.4 MB
Optical CD
Blu-ray disks
Flash storage

The 350 Disk Storage Unit consisted of the magnetic disk memory unit with its access mechanism, the electronic and pneumatic controls for the access mechanism, and a small air compressor. Assembled with covers, the 350 was 60 inches long, 68 inches high and 29 inches deep. It was configured with 50 magnetic disks containing 50,000 sectors, each of which held 100 alphanumeric characters, for a capacity of 5 million characters.
Disks rotated at 1,200 rpm, tracks (20 to the inch) were recorded at up to 100 bits per inch, and typical head-to-disk spacing was 800 microinches. The execution of a "seek" instruction positioned a read-write head to the track that contained the desired sector and selected the sector for a later read or write operation. Seek time averaged about 600 milliseconds.
With storage capacities of 5 million and 10 million digits, and the capability to be installed either singly or in pairs, the 350 provided the 305 system with storage capacities of 5, 10, 15 or 20 million characters.
An IBM RAMAC 305 with a 350 disk storage unit leased for about $3,200 per month back in 1957. Over a thousand of the 305 systems (one of IBM's last vacuum tube units) were manufactured before production ended in 1961, and the 305 was withdrawn in 1969.

Evolution of computer usage
First generation - science, army needs; Arithmetical calculations Second generation - government, big business needs; Storing data
Third generation - small and medium business needs; Useful Input and Output, smaller size Fourth generation - personal computers.

Extra information
http://www.stanford.edu/class/cs101/hardware-1.html
http://www.youtube.com/watch?v=IcrBqCFLHIY