CH1: binary system and hexadecimal

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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


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