How Data is Held

Question 1

What is Binary?

Answer 1

A base 2 number system represented through the digits 1 and 0.

Question 2

How is Binary stored in the Computer?

Answer 2

All data is held using on/ off signals

Question 3

Why is Binary Used in computers?

Answer 3

Computer systems are based on switches, which can only have two states, on or off. Binary numbers use two digits. Binary is high tolerance and robust.

Question 4

What Are Bits?

Answer 4

one binary digit 1 or 0

Question 5

What is a Byte?

Answer 5

a group of 8 bits

Question 6

What is a Nibble?

Answer 6

a group of 4 bits

Question 7

List the place values of a byte in descending order

Answer 7

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

Question 8

How to convert Binary to Denary

Answer 8

Add up the values of all place values where there is a 1

Question 9

How to convert Denary to Binary

Answer 9

Subtract place values from the denary starting with the highest. When you do this, put a 1 in that place value

Question 10

What is Hexadecimal

Answer 10

A base 16 number system. The digits 0-9 are the same as denary, while the digits 10-15 are A-F alphabetically.

Question 11

Why is Hexadecimal used

Answer 11

-easy to convert to and from binary
-easier to understand than binary

Question 12

How to Convert Denary to Hexadecimal

Answer 12

divide the denary number by 16. The quotient goes in the 16s column, the remainder goes in the 1s column.

Question 13

How to Convert Binary to Hexadecimal

Answer 13

Split the number into nibbles and write the matching hexa number under each group of 4.

Question 14

How to convert Hexadecimal to Binary

Answer 14

Write 4 bits under each hexa digit

Question 15

What is ASCII

Answer 15

A character set that represents each keyboard character (265 charas) as 8- bit binary codes.

Question 16

What is Unicode

Answer 16

An extended character code sequence. Old ascii files can still be read with unicode.The first 8 bits of unicode are the same as ascii, but it used 16-32 bits so needs more storage space.

Question 17

What is included in Unicode

Answer 17

• All global alphabets including braille.
• Currency, maths, map, and musical symbols
• Ancient languages eg. hieroglyphics
• Codes for emojis and other pictures
• Control and Formatting signs

Question 18

Who controls unicode

Answer 18

• the unicode consortium
• if you invent a new emoji or code you want to be used, you have to submit it to them . If they agree they will give it a code.

Question 19

How do different processors interpret unicode

Answer 19

Every make of computer / phone may interpret unicode characters slightly differently , eg apple vs android emojis look different.

Question 20

1)how to find the unicode for any character in python
2) how to find the character for any code number in python

Answer 20

(using the example c)
1) ord(“c”)

2) chr(67)

Question 21

how are negative binary numbers stored with sign and magnitude

Answer 21

the most significant bit stores the sign ( 0 for + , 1 for - )

Question 22

how are negative binary numbers stored with two’s compliment

Answer 22

The most signigicant bit is a negative value and the rest are positive

Question 23

what advantage does two’s compliment have over sign and magnitude

Answer 23

it can be used in calculations, whereas sign and magnitude can’t.

Question 24

how to convert a positive binary number to a negative using two’s compliment

Answer 24

flip all the bits, then increment the least significant bit

Question 25

list the four rules of binary addition

Answer 25

0+0 = 0
0+1 = 1
1+1 = 0 and carry 1
1+1+1 = 1 and carry 1

Question 26

how to subtract one binary number from another

Answer 26

turn the subtracted number negative using two’s compliment, then add both numbers together.

Question 27

How to use Binary shift to multiply or divide a binary number

Answer 27

Find the power of 2 for the number eg. x4 would be 2. Shift all the bits that many places to the left if multiplying, to the right if dividing

Question 28

what is overflow in multiplication or addition

Answer 28

if the result is too large, there will be a catty bit with nowhere to go. This is called an overflow and causes an error

Question 29

what is underflow in division

Answer 29

if the result of a division is a bit that “falls off” the right of the number, this is called underflow and causes an error.

Question 30

When is overflow not an error?

Answer 30

In subtraction.
if the subtracted number is smaller , the result will be positive. You will see an overflow bit, but this isn’t an error.

Question 31

What is Bitwise manipulation?

Answer 31

A way of processing binary values by changing the bits using logic rather than maths.

Question 32

What are three uses of bitwise manipulation?

Answer 32

-Encryption (XOR and others)
-Image processing. (OR processing can reconstruct an image from two damaged photos. )
-Noise reduction (AND can compare signal on both receivers)

Question 33

What are the three operators that can be used for bitwise manipulation?

Answer 33

AND = True if both are true
OR = True if at least one is true
XOR = True if the values are different

Question 34

How to perform masking?

Answer 34

The byte is altered by being merged with a second byte (the mask) using logical operations