Representing Data

Question 1

In what Language do computers operate in

Answer 1

Binary, 0s and 1s , everything we need to represent must be transformed in these 0s and 1s

Question 2

What is string concatenation

Answer 2

String contentation occurs when you use an addition operator between two strings to combine them into one.

Question 3

How does the addition operator act in different ways

Answer 3

It can perform addition on strings by combining them directly or it can computer the sum of numbers.

Question 4

Within binary what do the 1 and 0 represent

Answer 4

1 represents that an electrical signal has been read or transmitted whereas a 0 is the privation of an electrical signal

Question 5

What is a 64 bit computer

Answer 5

When the computer handles strings of 64 bits for transferring data. This results in double transfer speeds than previous 32bit machines

Question 6

How many bits did computer utilise in the 1980s when Sonic was released

Answer 6

8 bits

Question 7

What are the basic types of data supported by programming languages

Answer 7

• Integers - whole numbers
• Decimals - fractions
• Strings - sequences of characters

Question 8

How many bits are utilised to represent a character in a string

Answer 8

8 bits represenmting 256 different chracters
* The ASCII dataset uses 8 bits to represent 256 different character

Question 9

What is unicode

Answer 9

An alternative to ASCII useful for other languages and supports more than 8 bits per character allowing much more options

Question 10

What is meant by a denary base number system

Answer 10

A number system that is commonly utilised by humans such that a number 123 = 1 x 100 + 2 * 10 + 3 * 1, it utilises 10^n+1 to move a position with 10 combinations per space

Question 11

What is a base 2 number system

Answer 11

A base 2 number system utilises 2 possibilities per space and 2^n+1 to move each position up. Such that 0110 = 6

Question 12

What are some benefits of utilising binary in a computer system

Answer 12

Much hardware that is used with computers such as HDD and CDs that engrave pits to represent 1 and absence of for 0.
Similarly systems experience a lot of noise which can alter the states, if there are more states this will result in a higher likelihood of errors

Question 13

What is the range of an 8 bit number system

Answer 13

0 - 255

Question 14

What is hexadecimal notation

Answer 14

It is taking each group of four bits and representing it with a single digit

Question 15

Hexadecimal

Answer 15

0000 0 0
0001 1 1
0010 2 2
0011 3 3
0100 4 4
0101 5 5
0110 6 6
0111 7 7
1000 8 8
1001 9 9
1010 10 A
1011 11 B
1100 12 C
1101 13 D
1110 14 E
1111 15 F

Question 16

How do we represent negative numbers in sign bit representation

Answer 16

Utilising the left most bit as a sign bit, 0 indicated positive and 1 indicated a negative.

Question 17

What is the sign magnitude representation

Answer 17

It utilises the left most bit as a sign 0 being positive and 1 being negative, the rest of the bits represent their usual value

Question 18

What are the benefits of using a sign magnitude bit

Answer 18

Allows us to see if a number is negative or positive in value by evaluating the left most bit

Question 19

What happens to the range of bits when implementing sign magnitude bits

Answer 19

overall representation of numbers remains the same however two expressions for 0 and there is positive number impacted
2^8 = 0 -255 = 256 nums
2^8 = 2^8-1 = -127 – 127 = 256 nums
as 1 bit is used for sign magnitude

Question 20

What is a negative implication of using the sign magnitude representation

Answer 20

There are two representations of zero such that positive 0 = 0000 and negative 0 would be expressed as 1000.
Therefore the n bit representation has only ((2^n) -1) different values

Question 21

What is Twos complement

Answer 21

A more modern way of representing negative integers in a computer system such that the left most bit on represents a negative minimum value

Question 22

What is the range in twos complement

Answer 22

The range in twos complement would be (+2^(n-1) -1) to (2^(n-1))
such that in a 4 bit system with twos complement the range would be from 7 to -8

Question 23

What is overflow error?

Answer 23

In the computation of bit strings often there is a remainder bit that is ignored, skewing the result of the calculation.

Question 24

What are floating point numbers?

Answer 24

They are a solution to the problem that computers faced with expressing real numbers, that is continous data expressed in a limitted descrete format ignoring recurring decimals such as 0.3. These finite approximations are utilised instead.

Question 25

How will there be infintely many non represent able reals between any two floating point numbers

Answer 25

take some x and x’ such that they differ by the smalles amount allowed in our systems representation. Between x and x’ there will be a y which is a non representable real. between x and y there is another z and between y and x’ another a. This will result in a recursive issue and an infintely amount of on representable reals between two floating point numbers

Question 25

What is a rounding error

Answer 25

When utilising floating point numbers there is a small remainder often given by the computer rounding due to the previous issue that it cannot truly represent real numbers. If the rounding error becomes too noticeable due to multiple computiations we may actually recieve an unnacceptable result as a computation

Question 26

What is a numerically unstable calculation

Answer 26

When the rounding errors only affect the last few decimal places they can begin to grow during sequences of calculations resulting in the expected result being skewed

Question 27

Why would it be an issue to use floating point data types in an accounting software? What alternatives can we pose

Answer 27

The rounding error, numerically unstable calculations from floating point numbers can result in a level of uncertainty being introduced when it is unnecessary.
As an alternative we may introduce pennies stored as integers, at the end we can divide our results by 100 to limit uncertainty

Question 28

Explain this error posed by the program?
First number? 0.1
Second number? 0.2
Sum is 0.30000000000000004

Answer 28

As the computers do not have an exact representation of 1/10 it will approximate it to the closest value, in this case the value approximated too carries small decimal value which is expressed in the final calculation.

Question 29

What is the string data type in java

Answer 29

It is an array of characters

Question 30

Boolean values

Answer 30

True or False values often represented as a single byte, the smallest sequence of bits that can be fetched from RAM with the quickest efficiency

Question 31

Pigeonhole model of RAM

Answer 31

It is that the slots within the RAM act as slots for storing single bytes that are numbered and locations are noted to fetch and control what is transmitted to and fro them. Each pigeonhole is allocated a permanent number called its address

Question 32

What is a variable declaration

Answer 32

It is denoting the name and datatype of the variable before it is utilised

Question 33

What is a valid identifier

Answer 33

It is the name of the variable and must fit the code that is start with a letter. idenitifiers in java are case sensitive. If more than two words are utilised the second word and subsequent words are capitalised.

Question 34

What is the convention for writing class names?

Answer 34

That they begin with a capital letter

Question 35

What occurs at the declaration stage of a variable when denoting the variables type

Answer 35

It creates a box large enough to store values of the given type. And associates the idenitifier with the box storing a given value.

Question 36

What is the assignment stage of a variable

Answer 36

It is assigning a value of the given data type into the box we initialising, finally this process is known as intialisation, when the variable has been declared and assigned

Question 37

Operator precendence

Answer 37

It is the idea that some operators have precedence in performing over others such that 2 + 5 * 2 = 12 and not 14.

Question 38

What is the general convention when specifying order of calculations in java

Answer 38

Due to the 14 different operator precendence levels it is preferablet to utilise brackets

Question 39

How can you compare the lexicographical ordering of two strings in java

Answer 39

Utilising the first.compareTo(second) whicil will return a negative int if first is less than second, postive if greater and zero if theyre the same

Question 40

What is the difference between | and || in java

Answer 40

acts as a logical OR the || double stroke version represents a short circuit or where the left statement is evaluated first

Question 41

what is the difference between & and && in java

Answer 41

the && acts similarly as a logical AND with a short circuit feature evaualting the left statement first

Question 42

how does a conditional triadic operator work

Answer 42

predicate expression ? then expression: else expression
int b = 20 + ( (a < 0) ? -a : a); intialise b as twenty plus some conditional value

Question 43

What is the result of the assignment operator

Answer 43

It is that the value has been assigned

Question 44

What associative are the assignment operators

Answer 44

They are right associative which means that a string of assignments is evaulated right to left not left to right.

int a, b, c;
a = b = c = 35;
(a = (b = (c = 35)));

Question 45

What is a side effect of an expression

Answer 45

A side effect of an expression is that it appears to be other than it is , such that if we assign a = a +1 we are not mathemetically asserting a is itself plus 1 but a is assigned to the value of (a +1) which is 36 such that a = 36.

Question 46

What are op and becomes operators

Answer 46

They are methods of simplifying recalling a variable when assigning it a value

Question 47

Incrementing have special operators that are included within java

Answer 47

++ – are allowing incrementation and decrementation

Question 48

What is meant by prefix and postfix form

Answer 48

the same operators will act differently dependant upon the position of the operator
++ and –

Question 49

How does the prefix form work as

Answer 49

It will