2.1

Question 1

what is abstraction

Answer 1

the process of removing unnecesary details ad only including relevant details

Question 2

what is decomposition

Answer 2

breaking down complex tasks into smaller manageable tasks

Question 3

advantages of abstraction

Answer 3

allows the focus of what is important in problem solving

Question 4

advantages of decomposition

Answer 4

makes tasks easier to manage
different people can work on different tasks at the same time, reducing time
program components can be easily used in other components

Question 5

what is algorithmic thinking

Answer 5

a way of getting to a solution by identifying the individual steps needed

Question 6

what is an input

Answer 6

anything which needs to be supplied to the program to meet its goals

Question 7

what is usually created for an input

Answer 7

an appropriate variable name and data type

Question 8

how does algorithmic thinking work

Answer 8

• it creates sets of rules, an algorithm that follows it precisely leads to its solution
• for example, algorithms for doing multiplications will work 100% of the time if you follow the rules to get the result

Question 9

how are structure diagrams created

Answer 9

• they are produced using the method, step-wise refinement
• the problem is broken down using decomposition into smaller components (some problems will need more decomposition than others)
• the lowest level nodes should achieve a single task
• these can then be coded as a single or sub-program

Question 10

what do outputs do

Answer 10

they consider what the program needs to output
consider what form this output needs to take
consider an appropriate variable name and data type for any output

Question 11

what is a structure diagram

Answer 11

it is a method of designing a solution to a problem by illustrating the problem using decomposition

Question 12

what is pseudocode

Answer 12

an alternate text-based way of representing the sequence of steps in an algorithm

Question 13

advantages of using pseudocode

Answer 13

it allows us to lay down the logic of a problem without worrying about rules of syntax

Question 14

what is the terminal symbol (oval shaped) in a flow diagram

Answer 14

shows the start or end of a process

Question 15

what is the process symbol (rectangular shaped) in a flow diagram

Answer 15

shows that something is initialised, processed or calculated

Question 16

what is the decision symbol (diamond shaped) in a flow diagram

Answer 16

shows yes or no, true or false

Question 17

what is the input/output symbol (rhombus shaped) in a flow diagram

Answer 17

shows an input and output of data to the algorithm

Question 18

what is the subroutine symbol (rectangle with stripes) in a flow diagram

Answer 18

it is used to call a subroutine (separate function)

Question 19

what is the line in a flow diagram

Answer 19

controls passing between connected shapes

Question 20

name the different types of errors

Answer 20

• syntax errors, which are grammatical rules of programming language
• they stop code from being translated
• logic errors, which produce unexpected outputs
• on their own they will not stop programs from running

Question 21

what is tracing execution

Answer 21

• used for testing the accuracy of an algorithm for logic
• it involves examining a printed extract of program code and running through the program

Question 22

what is a trace table

Answer 22

• used for noting down any output the program produces
• each variable present in the program should have its own column in the trace table
• a new row should be added under any column if the state of a variable changes

Question 23

advantages of trace tables

Answer 23

they are a good way to track down logic errors in a problem

Question 24

how does binary search work

Answer 24

• calculate a midpoint in the data set
• check if that is the item to be found
• if not…
• if the item to be found is lower than the midpoint, repeat on the left half of the data set
• repeat until the item is found or there are no items left to check
• requires the data set to be in order of a key field

Question 25

advantages of binary search

Answer 25

more efficient than a linear search on average

Question 26

what is linear search

Answer 26

- starting from the beginning of a data set, each item is checked in turn to see if it is the one being searched for

Question 27

advantages of linear search

Answer 27

- does not require the data set to be in order - will work on any type of storage device - can be efficient for smaller data sets

Question 28

disadvantages of linear search

Answer 28

inefficient for larger sets of data

Question 29

what is bubble sort

Answer 29

it sorts an unordered list of items

Question 30

how does bubble sort work

Answer 30

- it compares each item with the next one and swaps them if they are out of order - the algorithm finishes when no more swaps need to be made - in effect it "bubbles" up the largest or smallest item to the end of the list in successive passes

Question 31

advantages of bubble sort

Answer 31

- it is the most inefficient of the sorting algorithms but is very easy to implement - this makes it a popular choice for very small data sets

Question 32

what is merge sort

Answer 32

uses division and creation of lists within lists to sort a list

Question 33

how does merge sort work

Answer 33

creates two or more identical variables from the original list, and solves them individually by merging separate lists in the correct order

Question 34

advantages of merge sort

Answer 34

- very efficient method of performing a sort - works well with larger data sets

Question 35

what is insertion sort

Answer 35

a sort similar to bubble sort except each variable is sorted into its correct data position one at a time

Question 36

advantages of insertion sort

Answer 36

- it is useful for small data sets - it is useful for inserting items into already sorted lists

Question 37

disadvantages of insertion sort

Answer 37

- usually replaced by more efficient sorting algorithms for larger data sets