1. Basics of computer Franck Theeten CABIN training, June 2013 Royal Museum for Central Africa, Tervuren

2. History 1937: Turing Machine: abstract representation of a computer (tape recorder) that can automatically solves any problem represented in its own alphabet 1941-1945 (WWII) first computers (Z1, Mark I, ENIAC) Circa 1980: development of the personnal computer (IBM PC) Circa 1997: development of the INTERNET (via the HTTP protocols) Circa 2005: development of the smartphones

3. Source: Wikipedia 1: screen 2: motherboard (intenal) 3: Central Processing Unit 4: Random Access Memory 5: Expansion connectors 6: Power supply 7: CD Reader 8: Hard disk drive 9: keyboard 10: mouse

4. The Motherboard Processing the information No permanent storage RAM CPU Bus (exchange circuit) Hard disk drive RAM: Temporary copy of the information (closer from the CPU)

5. Binary (I) Assembly is the fundamental language of the CPU Only 2 signs: 0 and 1 2 operations: addition and substraction Computer doesn’t count on base 10 but on base 2 (binary)

6. Binary (II) BIT: basic storage unit (‘0’ or ‘1’) Byte: word of 8 bit (for signs) 00000010 =>3 00000011 =>4 00000000 =>0 00000001 =>2 00000100 =>5

7. Binary (III) BIT: (‘0’ or ‘1’) Byte: word of 8 bits => basic storage unit 11111111 1 24 8 16 3264 128

8. Binary (IV) 11111111 1 24 8 16 3264 128 11111111 =>128+64+32+16+8+4+2+1 =255 00101011 =>32+8+2+1 =43 00010010 =>?

9. Alphabetical characters (I) Everything has to be translated to binary numbers Including letters ans signs –ASCII: transposition table of 7 bits=> only 128 characters (non accented) –ASCII with extension (8 bits)=> 128 signs from ASCII + 127 extensions (codepages) for several alphabets (different extensions) –Compatibility problems between the extensions –Non european characters not taken into account

10. Alphabetical characters (II) –Unicode: transposition table of 2 bytes (255*255 characters = 65 025 possibles characters) eg: ﻍ ♂♀  ĭ –UTF-8: unicode where the most current unaccented european characters are stored on 1 byte (win space!), the others characters on 2 bytes

11. Alphabetical characters (III) Note: The Windows notepad can easily convert documents from ascii to unicode o UTF-8 when clicking on « save as » Very useful for converting documents between software and platforms raw text documents only, not Word!.

12. Networks

13. Network : IP address A computer in a network is identified by an IP (‘Internet Protocol) address –32 bits/4 bytes : eg: 255.255.255.0 192.168.0.1 32 bits range (IPv4) is becoming too small at global scale: IPv6 next protocol with 128 bits/8 bytes

14. Network : IP address How to know your own ip adress? Windows: –open «cmd » –write ‘ipconfig’ Linux: –open «shell » –write ‘ifconfig’

15. Networks : IP address

16. Networks : address resolving On the Internet, as an individual customer, you more than likely have a temporary IP adress DHCP (Dynamic Host Configuration Protocol) server: the service of a provider allocating and changing the IP address of a single station (average duration lease : 3 days)

17. Networks : address resolving Most of time you don’t use an IP address, but a « textual » HTTP address (Hyper text transfer protocol) to acces resource: e.g: http://cabin.cybertaxonomy.africamuseum.be/page/cabin_call_2013 Reponse:

18. Networks : address resolving http://cabin.cybertaxonomy.africamuseum.be/ page/cabin_call_2013 The Server address The first « / » The page on the server

19. Networks : address resolving http://cabin.cybertaxonomy.africamuseum.be/ The Server address

20. Networks : address resolving http://cabin.cybertaxonomy.africamuseum.be This server address actually corresponds to an IP address: 193.190.223.52 The Server address

21. Networks : address resolving Inserting the IP in the browser also retrieves a page from the same server

22. Networks : address resolving Domain Name Server (‘DNS’): Service establishing the correspondance between the IP adress (193.190.223.52) and the domain name adress http://cabin.cybertaxonomy.africamuseu m.be http://cabin.cybertaxonomy.africamuseu m.be

23. Networks: address resolving http://cabin.cybertaxonomy.africamuseum.be Resolving an adress: from right to left (global to specific) –.be => service in Belgium –.africamuseum.be => server at the Royal Museum for Central Africa –cybertaxonomy.africamuseum.be => website from the cybertaxonomy service –cabin.cybertaxonomy.africamuseum.be => cabin part of the cybertaxonomy website => Several cascading DNS servers are used (first a global one to get the domain of country: «..be », and finally an internal one for the service inside of the museum

24. Networks: address resolving Resolving an adress: by cascading DNS –.be –.africamuseum.be –cybertaxonomy.africamuseum.be –cabin.cybertaxonomy.africamuseum.be

25. Networks: DNS On the Internet, an institution having his own websites probably uses a permanent Internet Address and DNS entry (≠ individual temporary DHCP address) –Commercial service from the Internet Sevice Provider or address available from public authorities

26. Network:nslookup How to know the ip adress of a website? Windows: –open «cmd » –write ‘nslookup ’ Linux: –open «shell » –write ‘nslookup ’

27. Network: nslookup Example of ‘nslookup’ query

28. Network: Port A computer in a network is identified by an IP (‘Internet Protocol) address 32 bits/4 bytes : eg: 255.255.255.0 A service in a computer is identified by a port number Eg. http://193.190.223.52:80 Port number for web page (enabled by default) Server adress

29. Network: port Port numbers, examples: – http://193.190.223.52:80 (web pages, can be omitted) – http://193.190.223.52:16 (FTP: service to directly uload or download files that can handle deconnection) – http://193.190.223.52:22 (secured FTP) – http://193.190.223.52:3306 (MySQL database) –…

30. Network: firewall firewallA firewall –Can disallow network traffic from/to a specific IP address (to block a server) Domain (to block a domain) Port (to block a software) –Can disallow Incoming traffic to prevent the installation of malicious programs ( spyware; trojan, worms) Outgoing traffic (to prevent already installed viruses to dispatch information of infect others-