A *computer* is a *counter*

Normally was a person that did calculations

Sometimes with the help of mechanical devices

During the 2nd World War people invented *electronic computers*

So, computers are devices handling **numbers**

September 21st, 2017

A *computer* is a *counter*

Normally was a person that did calculations

Sometimes with the help of mechanical devices

During the 2nd World War people invented *electronic computers*

So, computers are devices handling **numbers**

*Don’t worry*

Using numbers we can **represent** other things

In my country kids play this game:

They change vowels **A, E, I, O, U** by the numbers **1, 2, 3, 4, 5**

Then they write *H2LL4*

**Using the same idea** we can represent any text

… that we have represented *sounds* by *signs* for centuries

The key word here is **represent**

There are three things in the Universe

- Matter
- Energy
- Information

Information can be put in digital (numeric) form

- Images
- Audio
- Movies

not yet

- smell
- taste
- tact

Computers handle numbers

Numbers represent information

Computers can transform and transfer information

- Computer
- (English) counter, calculator
- Ordinateur
- (French) sorter, gives order to data, handles data
- Bilgisayar
- (Turkish) Information/Data counter

Who invented computers?

Do you have a computer at home?

What do you use it for?

- calculate formulas
- solve (some) equations
- store
**and retrieve**huge quantities of data - find patterns in data
- find data matching a pattern
- transform data in useful ways
- compress data
- move data at low cost without distortion

First usage of electronic computers was to solve complex equations

This approach enabled landing on the moon

Let’s find the value \(x\) that satisfies \[24x^3-70x^2+19x+15=0\]

Let us put a name to the formula. Let’s call it \(f(x)\). \[f(x) = 24x^3-70x^2+19x+15\]

We want to find \(x\) that makes \(f(x)=0.\) We can write \[f(x) = (24x^2-70x+19)x+15\] or even \[f(x) = ((24x-70)x+19)x+15\]

- Take a piece of paper and
**write**\(x\) in the first line **Write**24**Multiply**the last two numbers**Add**-70**Write**\(x\) (from the first line)**Multiply**the last two numbers**Add**19**Write**\(x\) (from the first line)**Multiply**the last two numbers**Add**15**Compare**to 0

We solved a complex mathematical question using a simple set of rules

- write
- multiply
- add
- compare

This decomposition in simple steps is called **a program**

In this exercise we used

- memory (paper)
- arithmetic/logic units (you: adding, multiplying, deciding)
- input/output (me)

Many different questions can be solved with the same rules

It is just a matter of changing the *program*

First electromechanical computers were like us: A sequence of devices, each one feeding the next

Changing the program required physical change of pieces

John Von Neuman realized that the set of steps can be also stored in memory (coded as numbers, obviously)

We only need to include

- a
*pointer*to the current instruction - a system to decide which arithmetic/logic rule apply

This is called *Central Process Unit* (CPU)

Since old times physical tools are called *hardware*

That includes al the physical parts of the computer (what you can kick)

Programs determine the function of the computer, but they are not “physical”.

That is *software* (what you can only insult)

All cell components are hardware

The sequence of the DNA is the software

Is a *general purpose* device that can

- read, process and write numbers
- (and things that can be represented by numbers)
- to and from the
*memory*

- following a
*program*stored also in the memory- many simple steps

Changing the program changes the purpose of the machine

- How information is coded in numbers
- How these numbers are stored and organized
- How we interact with computers