Section 6, 7, 8 Data Types

Question 1

Integer

Answer 1

● A whole number
● Zero is an integer
● Negative numbers are integers
● Can’t have a fractional part
● Useful for counting things

Question 2

Real

Answer 2

Positive or negative numbers
Can, but do not necessarily, have a fractional
part
Useful for measuring things
All integers are real numbers

Question 3

Character

Answer 3

● A single symbol used by a computer
● The letters A to Z
● The numbers 0​ to 9
● Symbols like %, £

Question 4

String

Answer 4

A collection of characters
● Can be used to store a single character
● Can also be used to store many characters in
succession
● Useful for storing text
● Don’t cut off leading 0​s like numeric type

Question 5

Boolean

Answer 5

● Restricted to True​ and False
● Useful for recording data that can only take two
values

Question 6

Least significant bit

Answer 6

furthest to right

Question 7

most significant bit

Answer 7

furthest to left

Question 8

-ve number sign and magnitude

Answer 8

Leading 1 is like adding a - sign
0 is a + sign

Question 9

Two’s Complement

Answer 9

● Has the added advantage of making binary arithmetic with negative numbers much
more simple
● Works by making the most significant bit negative
● Converting to two’s complement is as simple as flipping all of the bits in the positive
version of a binary number and adding one

Question 10

Two’s complement, subtraction in binary

Answer 10

● Two’s complement makes subtraction in binary easy
● Subtracting a number from another is the same as adding a negative number
● To subtract in binary, use binary addition with a negative two’s complement number

Question 11

Floating point numbers can be split into two parts:

Answer 11

○ Mantissa
○ Exponent

Question 12

Normalisation

Answer 12

● Maximises precision in a given number of bits
● To normalise a binary number:
○ Adjust the mantissa so that it starts 01​ for a positive number of 10​ for a
negative number

Question 13

Character Sets for Representing Text

Answer 13

● A published collection of codes and corresponding characters
● Can be used by computers for representing text
● Two widely used character sets are ASCII and Unicode

Question 14

ASCII

Answer 14

American Standard Code for Information Interchange
● The leading character set before Unicode
● Uses 7 bits to represent 27
= 128 different characters
● ASCII soon came into trouble when computers needed to represent other
languages with different characters

Question 15

ASCII

Answer 15

American Standard Code for Information Interchange
● The leading character set before Unicode
● Uses 7 bits to represent 27
= 128 different characters
● ASCII soon came into trouble when computers needed to represent other
languages with different characters

Question 16

Unicode

Answer 16

● Solves the problem of ASCII’s limited character set
● Uses a varying number of bits allowing for over 1 million different characters
● Many characters have yet to be allocated
● Enough capacity to represent a wealth of different languages, symbols and emoji

Question 17

Arrays

Answer 17

An array is an ordered, finite set of elements of a single type.
● A 1D (one- dimensional) array is a linear array.
● A 2D (two-dimensional) array can be visualised as a table/spreadsheet.
● When searching an array, first go down the rows and then across the columns.
● A 3D (three-dimensional) array can be visualised as a multi-page spreadsheet
○ An element in a 3D array using: threeDimensionalArray[z,y,x]
z = array number, y = row number, x = column number.

Question 18

Records

Answer 18

● More commonly referred to as a row in a file,
● A record is made up of fields, and is widely used in database

Question 19

lists

Answer 19

● Consists of a number of items, where items can occur more than once.
● Data can be stored in non-contiguous locations and be of more than one data type.

Question 20

Tuples

Answer 20

● An ordered set of values of any data type .
● Cannot be changed: elements cannot be added, edited or removed once initialised.
● Initialised with regular brackets rather than square brackets

Question 21

Stacks

Answer 21

● Last in first out (LIFO) data structure:
○ Items can only be added to/ removed from the top of the stack.
● Used to reverse actions, eg. back buttons and undo buttons use stacks
● Can be implemented as a static or dynamic structure.

Question 22

Queues

Answer 22

● First in first out (FIFO) data structure:
○ Items are added to the end and are removed from the front of the queue.
● Used in printers, keyboards and simulators.
● Linear queue: items are added into the next available space, starting from the front.
○ Items are removed from the front of the queue
○ Uses two pointers: pointing to the front and back of the queue.
○ Use space inefficiently, as positions from which data has been removed
cannot be reused

Circular queues have a rear pointer that can loop back to the front of the queue and
utilise empty space at the front.
○ Are harder to implement.

Question 23

6 stack operations

Answer 23

isEmpty() Checks if the stack is empty
push(value) Adds a new value to the top of the stack
peek() Returns the top value of the stack without removing it
pop() Returns and removes the top value of the stack
size() Returns the size of the stack
isFull() Checks if the stack if full

Question 24

4 queue operations

Answer 24

enQueue(value) Adds a new item to the end of the queue
deQueue() Removes the item from the end of the queue
isEmpty() Checks if the queue if empty
isFull() Checks if the queue is full

Question 25

Inputs to truth tables are called

Answer 25

literals

Question 26

Karnaugh maps headings

Answer 26

00
01
11
10

Question 27

Karnaugh map usage