CH1: binary system and hexadecimal
How many hexadecimal digits are in a MAC Address
48 bits 6 pairs of hexadecimal digits NN-NN-NN-DD-DD-DD NN:NN:NN:DD:DD:DD
byte
8 bits
Denary System
Number system with base 10
memory dump
Output of memory contents onto the printer or screen. Usually represented in hexadecimal, for *debugging*. *powerful fault-tracing tool*
URL
Uniform Resource Locator
what is a register
a group of bits (when microprcessors are used to control devices like robots , *register are used as apart of the control system*)
binary system
a number system that has just two unique digits, *0 and 1*, called bits 2⁷,2⁶,2⁵,2⁴,2³,2²,2¹,2⁰ 128,64,32,16,8,4,2,1
why MAC addresses are used
allows all devices to be *uniquely* identified
Binary digits is also referred as
bit
what is the smallest unit memory in the computer
byte (*are always multiples of 8*)
how to add hexadecimal numbers
change to binary (n.b you carry when you overflow from 1)
% denotes that------- is used
hexadecimal
what is the advantage of typing the web address as hexadecimal
higher security unlikely to fall into fake addresses
where is the MAC address located
in the NIC network interface card
what does the *first half* of the mac address represent
manufacturer of the device
why some big problems may happen if changed the MAC address
may be not unique, so clashes will happen
how to convert from binary to denary
multiply the 0 or 1 with the column value
example use of binary
register
what does the *second half* of the mac address respresnt
serial number
HTML
used when writing or developing web pages (not a programming language, it is a mark-up language) - specify the color of text -#RGB
11101110
128+64+32+8+4+2= 238
1 Megabyte (MB)
2²⁰ 1,048,576 bytes
1 Gigabyte (GB)
2³⁰ 1,073,741,824 bytes
1 Kilobyte (KB)
2¹⁰ 1024 bytes
1 Terabyte (TB)
2⁴⁰ 1,099,511,627,776 bytes
1 pentabyte (PB)
2⁵⁰ 1,125,899,906,842,624
ASCII code
(american standard code for information interchange) -each key on the keyboard is given a binary value -can be represented as hexadecimal values
how to convert from denary to binary
*1)trial and error* subtract the number with the smallest nearest number from the column values *2)successive division of 2* remainders are then read from BOTTOM to TOP
how to convert from denary to hexadecimal (most difficult)
*1- trial and error* placing hexadecimal digits in the appropriate position so that the total is equal to the number *2- repetitive division of 16* reminder are the read from BOTTOM to TOP *3- Change it to binary then to denary*
explain what the hexadecimal code in MAC address represents
- hardware address - unique address found in the NIC -48/64 bits -- 12/16 hexadecimal digits - first 6/8: manufacturer code - second 6/8: serial number
what are the two types of MAC addresses
-*UAA* Universally administered MAC address -*LAA* locally administered MAC address
examples of low-level languages used by software developers
-Machine code -Assembly code
uses for binary numbers stored in register
-data -ASCII value -number -part of image -sound -instruction
why better to use hexadecimal rather than binary in assembly code and machine code
-easier -faster -less error prone to write the codes
Mark up language is used in
-processing -definition -presentation of text
describe the problem that could be caused if the binary number is shifted (five) places to the *right*
-run out of places to the right of the register -right-most 1 would be lost -loss of precision
UAA
-set by the manufacturer in the factory
table of 16
1) 16 2) 32 3) 48 4) 64 5) 80 6) 96 7) 112 8) 128 9) 144 10) 160 11) 176 12) 192
benefits of hexadecimal *in computer science*
1- can represent *16 bit* word in only *4 hex digits* 2-it is easier to *convert back* to binary if necessary
explain why programmers would prefer to see the contents of the locations displayed as hexadecimal rather than binary, when debugging his program that reads the key presses
1- easier to identify values 2- easier to spot errors
why programmers prefer hex over binary
1- easier to understand 2- easier to debug 3- shorter, so less space on the screen
describe how other colors are created
1- hex values from 0 to F are combined together to create a hex code 2- different combinations in hex codes will create different shades
Describe how the microprocessor can determine when to sound the clock alarm
1- read value in the register of the *present time* 2- microprocessor checks the value *against the alarm timing* stored in the register 3- if values in corresponding registers are the same 4- the microprocessor sends a *signal* to sound the alarm
how to convert from binary to hexadecimal
1- split the binary number into groups of 4 bits 2- take each group of 4 bits and convert it into the equivalent hexdecimal
how to convert from hexadecimal to binary
1- take each hexadecimal digit 2- write it down the 4-bit code which corresponds to the digit
why MAC address needs to be changed using *LAA*
1-certain software in the *mainframe system* needs all the MAC addresses of devices to fall into a *restricted format*, --necessary to change MAC addresses to ensure follows the correct format 2- *bypass a MAC address filter* on a router of *firewall* (only allows certain format, so to stop it from blocking it) 3-*get past certain types of network restrictions* (it may be necessary to emulate unrestricted MAC address, hence it may require the MAC address to be changed on certain devices connected to the network)
uses of the hexadecimal system
1-memory dumps 2-Hypertext Mark-up Language (HTML) 3-Media Access Control (MAC) 4-Web addresses 5-Assembly code and machine code
how to convert from hexadecimal to denary
1-take each hexadecimal digit and multiply it by its place value 2-add the totals together
Hexadecimal Number System
A number system consisting of 16 distinct symbols — 0-9 and A-F — which can occur in each place value. 65,536 4,096 256 16 1 16⁴, 16³, 16², 16¹, 16⁰
web addresses and URL can be represented by
ASCII code
MAC address
Media Access Control Address - number *uniquely* identifies a device on the internet
