Lesson

Binary data is base 2 as in 1's or 0's

a bit is 1 number, 4 bits are a nibble and 8 bits are a byte

Kilobyte=1024 bytes because it is 2^10

          128,64,32,16,8,4,2,1

132=      10000100

96=        01100000

10=        00001010

254=      11111110

67 =       01000011

102=      01100110

59 =       00111011

            128,64,32,16,8,4,2,1

00101111 = 47

01111110 = 126

11111111 = 255

11011101 = 29+192 = 223

11001000 = 8 + 192 = 200

           8,4,2,1

0101+         1010+       0010+   1100+       1110+

0110            0100        0011      0001         0010

_____           ____         _____     ____          ____

1011 = 11   1110=14   0101=5 1101=13  10000=16 (stack overflow)

1                                     1                          111

128,64,32,16,8,4,2,1

10000000+            00111110+         011000010+

00100000              00110010           000000100

_________              _________          ___________

10100000    =160  01110000=112  011000110=102

                                 11111          

8,4,2,1  012346789ABCDEF

01101010 =   6A

11111110 =    FE

00100000 =   20

00100010 =    22

A1= 161

DF= 208+15= 223

79= 112+9=121

33= 51

C4= 196

7B=123

Gigabyte=1024^2 kilobytes

Petabyte=8*1024^5

Yotta=8*1024^6

6). What is base 10 base 2 and base 16? Denary, binary, hexadecimal

7). Hexadecimal is used to convert binary because each character represents a nibble

8). Write a simple Python program that works out bits/bytes or converts binary to denary or hexadecimal

 

Domain name system

The DNS server would convert the domain name into the IP adresses that your computer uses to transfer data on the website so you can use it. The domain name may seem unnecessary because it is just the IP adress that is needed but it means that people who use the sight regularly can remember the domain name and access the site more easily. It also means that search engines can find the sites related to what you want to find because IP adresses don't give any information about the sight.

However, the domain name system has some problems, it means that the Internet is centralised around the DNS servers so if the DNS breaks down like it almost did a few years ago then the whole internet could crash.

As a company controls it, it can be controlled by the laws of the countries it is based in so could mean that not everyone can share information online which was what the Internet was made for.

Powtoons

http://e.customeriomail.com/e/c/eyJlbWFpbF9pZCI6Ik1qQTNORG9XQW5JQ1pBQUNjd0FYSlZMbUdnRkxBNmNFRUJWV0dGUy1yWUFCWlRvek1URTVORFppT1MxaE1HUmlMVEV4WlRRdE9HSmpOaTAwWWpGa1l6WTVNRFF6WXpnNk9EazROemdBIiwicG9zaXRpb24iOjIsImhyZWYiOiJodHRwczovL3d3dy5wb3d0b29uLmNvbS9zaG93L2RCeklBeHo2cmlUL2NvbXB1dGluZy1rZXl3b3Jkcy8ifQ==

Databases

Databases: are permanent (persistent), Related, Organized and Usually stored for a organisation 

External view - what user sees, designed to be helpful for task

Conceptual view - how data is organised

Physical view - how data is actually stored

Flat file - single table, suitable for simple data requirements

Hierarchical - for when data relate to each other like branches on a tree

Serial file - one after the other, stored adjacently

Sequential - data stored in order of important keys values

Exam corrections

For question 2, it was bus topology because there was one linking cable connecting all the devices.

The device was a 

The functions are to share data between workstations, restrict data use for individual accounts

Internet

Internet: worldwide network of networks, use TCP/IP to control data exchange.

WWW: World Wide Web, is all the public web sites on the internet.

TCP/IP: Transmission Control Protocol - makes sure the correct data is delivered from client to server, detects error.  IP - moves data between networks.

Redundancy:   A backup system if something fails

Digital and analogue internet: was made of phone system so used analogue system, analogues have to be decoded so digital ones are better as they don't need to be decoded.

bandwidth:  speed of data transmission normally in bit rate

Broadband:  high speed data transmission that carries large amount of data at once through a cable.

Networks

LAN:

    Local area network, connected set of computers and other devices, each device is called a node.

    Advantages-

        Allows communication between workers, data sharing, sharing peripherals, upgrade easier,

        distributing processing.

    Disadvantages-

        Expertise needed to set up, strong passwords

    Hardware-

        NIC-network interface card, every node needs one to connect with LAN produce electrical signals

        HUB-a device that connects nodes together, makes them act as one unit, all data packets are                           transmitted

    A router forwards data packages between computer networks

    Switches allow nodes to communicate with each other 

    Wireless access point, means no building work needed, flexible, visitors can access but has a       

    Low performance and security issues.

Peer to peer:   Could be slow because of data collisions and shared processor power.

Client server:   One or more computers are the server and they have software, data and peripheral access that it shares, in control of what they can do, records what is used for, extra security and requires a log in.

Topology: physical layout of network

Star topology: shared link to a server, few data collisions, fast and can have independent sections.

Ring topology: all connected by one cable, fast and no collisions as one way traffic but any problems would affect all of them.

Bus topolgy: one linking cable with nodes coming of it, cheap but lots of data collision, slows down in heavy traffic, any problems affect all.

WAN: wide area network, structure could be telecoms companies

VPN: virtual private network, better security, uses Internet.

Protocols: rules for device communication

   DNS: translates domain names into IP adresses

   TS/SSL: secure communications

   FTP: copy files from another host

   Gopher: early way of searching on internet

   HTTP: for web pages

   IMAP: method for accessing emails

   POP3: another way to access emails

   Telnet: text communications on a network

IP adresses: code that identifies the node

MAC: communicate with physical layer of network

Packets: data is put into packets when it needs to go to another adress

Security

   Access levels: uses log in names to grant privileges

   Passwords: must be something that people couldn't guess and should be changed often

   Encryption

Policies: tell users what is expected from them