flashcards

Question 1

why a queue is used instead of a stack

Answer 1

• queues are first in first out
• so that the data will be stored in the order they arrive

Question 2

why is dequeue() a function and not a procedure

Answer 2

because it returns a value

Question 3

what does best time O(n) complexity mean

Answer 3

• processing time is linear
• directionally proportional to the size of the list

Question 4

what does average and worst tine O(n²) complexity mean

Answer 4

• processing time is proportional to the square of the number of items in the list
• quadratic

Question 5

what does worst space O(1) conplexity mean

Answer 5

constant amount of memories used

Question 6

which direction is breadth and depth in a binary tree

Answer 6

• breadth = horizontal
• depth = vertical

Question 7

backtracking in a binary tree

Answer 7

when the value is found, the algorithm backtracks following the previous nodes

Question 8

explain the difference between branching and iteration

Answer 8

• branching chooses which code is run next
• iteration loops through the same code

Question 9

what does MOD do

Answer 9

returns the remainder

Question 10

what is one benefit and one drawback of using iteration instead or recursion

Answer 10

• benefit = can’t run out of memory
• drawback = code is longer, therefore mode difficult to understand

Question 11

explain how decomposition can aid the design of a program

Answer 11

• breaking down code into subroutines
• in order to make it a more manageable problem which is easier to understand
• can tackle each sub problem independently

Question 12

define pipelining

Answer 12

the result of one process leads to another

Question 13

name 4 features of an IDE and what they do

Answer 13

• syntax highlighting = the IDE can make the text bold, highlighted, coloured etc to highlight accidental syntax errors
• debugging = runs through code and fixes any errors or bugs
• testing = allowes developers to run code locally (without exiting software) before it is implemented in other developers’ code
• variable watch widow = allows a developer to monitor the value of a variable during execution (during debugging)

other marks
* reduce spelling errors
* fewer mistakes
* user friendly for novices
* increase speed of testing/finding errors

Question 14

different examples of how abstraction simplifies visuals

Answer 14

• no actual images shown
• items are names/labeled
• simplified layouts with shapes

Question 15

explain the need for abstraction in the production of a visual

Answer 15

• reduces complexity of design,
  
  • programming
• reduce memory/processing requirements
• could involve a large number of images which take up excessive memory
• reality contains things that aren’t related to a computer program

Question 16

what is meant by problem recognition and decomposition

Answer 16

• recognition = identifying what the problem is(scope)
• decomposition = breaking down problem into smaller parts (subroutines)

Question 17

define the term ‘data mining’

Answer 17

searching through data to find trends, specific information

Question 18

identify 3 pieces of information that data mining could provide a company about sales and how the company could make use of it

Answer 18

• identifying customer trends
  
  • to identify items to sell/offers to send customers
• identify which stores are making the most profit
  
  • to identify what other stores in the area are doing well
• which items are not selling well
  
  • to replace them with other items

Question 19

define ‘performance modelling’ and one way it can be used to test a system

Answer 19

• test the behavious of the system before it is used
• testing it with a large number of customers/items/orders

Question 20

one benefit of creating reusable program components

Answer 20

• components can be used in a future program
• do not need to be rewritten/saves time

Question 21

differences between a graph and a tree

Answer 21

• a graph has cycles
• tree has a hierarchy
• graphs an be directed/undirected

Question 22

2 advantages of how using visualisations

Answer 22

• visualisations benefit humans rather than computers
• present information in a simpler form to understand
• visualisations can best explain complex situations

Question 23

explain why a recursive algorithms use more memory than iterative algorithm (2)

Answer 23

• each recursive call creates new variables
• iteration reuses the same variables

Question 24

describe how a 1D array can be set up and used to push and pop items as a stack

Answer 24

• define the size of the array
• use a pointer to point to the top of the stack
• when an item is pushed the pointer is increased by one
• when an item is popped the poiner decreases by one

Question 25

explain the similarities and differences between a record structure and a class

Answer 25

* both store data of different types * both can have multiple instances * record is a data structure * a class is a template for making data strutures(objects) * class can include visibility of properties / private

Question 26

define 'queue' (2)

Answer 26

* data stucture * that is FIFO

Question 27

define 'stack' (2)

Answer 27

* data structure * that is FILO

Question 28

how does a private attribute improve the integrity of data (3)

Answer 28

* properties are encapsulated and can only be accessed through their mehods * cannot be changed/accessed accidentally * innapropriate data can be caught before entered

Question 29

how could someone amend a program to make sure the items and queue sill exist and are used the next time the program is run (2)

Answer 29

* store the items and queue to an external file when the program closes * load the items and queue from the program when it starts

Question 30

what is a global variable

Answer 30

a variable that is declared in the main program, outside of any subroutines and can be used anywhere in the program

Question 31

what is object oriented programming

Answer 31

a programming paradigm where the system is viewed as a set of objects each with their own data (attributes) and procedured (methods) that can interact with each other.

Question 32

what is a procedure

Answer 32

* a subroutine that is called by simply writing its name in the code * procedures do not have a return a value in the program

Question 33

define recursion

Answer 33

a programming subroutine where a section of code calls itself

Question 34

what are heuristics

Answer 34

a ‘rule of thumb’ algorithm which can produce a sub-optimal solution for a difficult problem as an approximation

Question 35

what is branching

Answer 35

using IF statements

Question 36

describe iteration

Answer 36

* count-controlled code = block of code executed a certain number of times * condition-controlled code = block of code is executed while a condition is met * e.g. for i in range loops * iteration uses FOR, WHILE, REPEAT UNTIL loops.

Question 37

what do push(), pop() and peek() do in stacks

Answer 37

* push = adds an item into the stack * pop = removes the most recently added item into the stack * peek = without modifying the stack, return the value of the last element added

Question 38

what is a sequence

Answer 38

code is executed line-by-line, from top to bottom

Question 39

2 advantages and 2 disadvantages of recursion;’;

Answer 39

*advantages* * can be represented in fewer lines of code * easier to express some functions recursively e.g. factorial *disadvantages* * risk of stack overflow if memory runs out * difficult to trace