1. Introduction to computer science - Lecture 1
The subject of computer science, history, positional systems

2. The subject of computer science
What is computer science? Is it science or engineering?
Who is a computer scientist and what does this person do?
What is information technology (IT)?

3. The subject of computer science
The subject of computer science is information.
Computer science deals with storing, transferring and processing information.

4. What is information?
[łac. informatio ‘idea’, ‘explanation’, ‘message’]
Encyklopedia PWN
A feature of some objects.
Klemens Szaniawski, hasło Informacja w: Filozofia a nauka, 1987, s (own translation)
A relation between the elements of the sets of some objects, whose main purpose is decreasing of the unsureness (undefinedness)
Grzegorz Lissowski, hasło Informacja, w: Wielka Encyklopedia Powszechna, 2002, s (own translation)

5. Information vs data
Information is an abstract object, which encoded as data can be stored, transferred and processed. Data can also be used for controlling the behaviour of various system.
Data is formal representation of specific content.
Source: Wykład z Podstaw Informatyki, dr Jan Kaczmarek

6. Who is a computer scientist?
programmer
administrator
graphic designer
...

7. Programmer

8. Network administrator (Cisco)

9. Can a computer scientist leave his desk?
system analyst
system designer
implementation manager
tests coordinator
...

10. Very brief history of computer science (lecutres of Dr. Jan Kaczmarek)
ca. 2600BC - counting devices called “abacus”
IV century BC - Euklides formulates the first algorithm (greatest common divisor)
IX century AD - Persian mathematician Muhammed Alchwarizmi (Muhammed ibn Musa al-Chorezmi) - gave the rules for adding, subtracting and multiplying numbers. His name in latin is ALGORISMUS.

11. Very brief history of computer science
Wilhelm Schickard ( ) counting machine (4 basic operations)
Blaise Pascal ( ) summing machine (Pascalina)
ca Gottfried Wilhelm Leibnitz ( ) – counting machine, rediscovery of Chinese binary system
Charles Babbage ( ) differential machine, plans for an analytic machine, programmable by perforated cards.

12. Very brief history of computer science
Ada Augusta King, countess Lovelace ( ), translated the dissertation about the analytic machine and formulated the rules of computing Bernoulli numbers with the help of that machine - first computer program.
1887 r - Herman Hollerith ( ) counting machine for statistical data (census).

13. Very brief history of computer science
1946 – John von Neumann ( ) - architecture of modern computer
– Konrad Zuse ( ) - Z1, Z2, Z3 - first calculators
Atanasoff-Berry Computer - a machine for solving systems of linear equations.
– ENIAC (Electronic Numerical Integrator And Computer) - electronic calculator.

14. Very brief history of computer science
– the computers EDSAC (UK) and UNIVAC
New companies:
IBM (International Business Machines )
ACM (Association for Computing Machinery ), a professional association.
1947 – the invention of a transistor
1950 – Polish computer of the 0-th generation
1955 – transistors replaced the electron lamps
1958 – the invention of a chip
1958 – XYZ - first computer built and operated in Poland
1960 – first mini-computer PDP-1

15. Very brief history of computer science
1964 – computers IBM/360
1971 – Intel 4004 processor (2300 transistors, speed 740 kHz) serial production of microprocessors
1974 – processor Intel 8080 (4800 transistors, speed 2 MHz)
1975 – first home microcomputer Altair 8800 (firma MITS)
processor Intel 8080, 256B RAM, speed 2 MHz
1977 – computer Apple II
1981 – first microcomputers IBM PC

16. Numeral systems
The decimal system is not as obvious, as we might think.
Egyptians were writing numbers in an additive system:
Source: discoveringegypt.com

17. Numeral systems Romans also used an additive system:
Source: wikihow.com

18. First positional systems
The first positional system was used by Babylonians. It was a 60-based system. The Babylonians were the inventors of a “0”.
The decimal positional system was introduced in India. However, the numerals were coded as words, which formed whole sentences or even poems.

19. Converting between positional systems
A number c1c2...cn in a system with the base p has the value:
c1pn-1+c2pn cn
Let’s try to compute the value of a number 251 in a 6-based system.

20. Converting between the decimal and binary system
Division
remainder
72:2
36:2
18:2
9:2 1
4:2
2:2
(72)10=( )2

21. Converting between binary and octal
In order to quickly convert a binary number to the octal system, one should group the binary digits in groups of three, starting from the right side:
( )2=(1|101|010|101|011)2
Next, one should convert the groups into the octal digits: (15253)8
How to convert from octal to binary?
How to convert between binary and hexadecimal?

22. Thank you for your attention!