2.2 Problem solving and programming

Question 1

What are the three types of programming constructs?

Answer 1

sequence
branching
iteration

Question 2

Explain what we mean by sequence as a programming construct

Answer 2

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

Question 3

Explain what we mean by branching as a programming construct

Answer 3

when a particular block of code is met if a specific condition is met

examples are if and else statements

Question 4

Explain what we mean by iteration as a programming construct

Answer 4

blocks of code which loop

can be either:
count controlled- blocks of code looping over a certain number of times
condition controlled- blocks of code looping until a specific condition is met

examples are DO, WHILE, FOR loops

Question 5

Explain recursion

Answer 5

When a subroutine calls upon itself during its execution
-continues until a stopping condition is met

Question 6

What are some advantages to using recursion? (2)

Answer 6

-code can be represented in fewer number of lines
-easier to express some functions recursively e.g. factorial

Question 7

What are some disadvantages to using recursion (2)

Answer 7

-risk of stack overflow if memory runs out
-difficult to trace

Question 8

What is a scope and how is this related to variables?

Answer 8

-variables can be defined with a global or local scope
-a scope is the section of code where the variable can be accessed

Question 9

Explain what local variables are and their characteristics

Answer 9

variables which can only be accessed within the subroutine where they were defined

Question 10

Explain what global variables are and their characteristics

Answer 10

variables which can be accessed through the whole program

Question 11

What are some +/- of using local variables? (3, 1)

Answer 11

+won’t affect other sections of code
+deleted once subroutine ends so doesn’t take up lots of memory
+multiple local variables with same names but in different subroutines can exist

-need to keep declaring in different sections of code if needed there

Question 12

What are some +/- of using global variables? (1, 3)

Answer 12

+useful for values that need to be used by multiple parts of the program

-if changed, it will affect other areas of code where it has been called upon
-can unintentionally edit it
-not deleted until program terminates so requires more memory

Question 13

What is modular programming?

Answer 13

a technique used to split large/complex programs into smaller, self-contained modules

Question 14

Why is modular programming useful? (3)

Answer 14

-easier to divide tasks between a team and manage projects
-simplifies the process of testing and maintenance (each component can be tested individually
-improves reusability of components

Question 15

Explain a top down design/modules

Answer 15

-technique to modularise programs
-problem is broken down into subproblems until each is is represented into individual, self-contained modules which perform a specific task
-modules form blocks of code called subroutines

Question 16

Explain functions

Answer 16

-blocks of code which perform a specific task
-functions return a value
-can pass parameters by value or by reference

Question 17

Explain procedures

Answer 17

-blocks of code which perform a specific tasks
-procedures output values
-can pass parameters by value or by reference

Question 18

What do we mean by passing a value by reference?

Answer 18

-address of parameter is given to the subroutine
-value of parameter will be updated at the given address
-changes the original data stored

Question 19

What do we mean by passing a value by value?

Answer 19

-a copy of the value is passed to the subroutine and discarded at the end
-the original value stored is unaffected

Question 20

What is an IDE?

Answer 20

integrated development environment
-provides a set of tools to make it easier for programmers to write, develop and bug code

Question 21

What are some features of IDEs? (7)

Answer 21

-stepping (executes line by line to see how each line effects program)
-variable watch (observes the contents of variable and how they change in real time through execution)
-debugging tools (provides errors in lines during run-time)
-autocompletion
-syntax highlighting
-breakpoints

Question 22

What is a class?

Answer 22

a template for an object
-defines state and behaviour for an object

Question 23

How can we define the state and behaviour of an object?

Answer 23

state- using attributes
behaviour- methods

Question 24

What is an object?

Answer 24

a particular instance of a class

Question 25

What is encapsulation?

Answer 25

when attributes cannot be directly edited (declared as private)
-can only be altered by public methods
-makes the program less complex by protected data from being edited

Question 26

How do top down designs use encapsulation?

Answer 26

each module is designed to be self-contained

Question 27

What do we mean by divide and conquer? Where could this be used?

Answer 27

problem solving technique
simplifies complex problems quickly

three parts:
-divide (problem in 1/2 with every iteration)
-conquer (each subproblem is solved, often recursively)
-merge (solutions to subproblems are recombined)

examples: quick sort, merge sort, binary search

Question 28

What are the various problem solving strategies? (7)

Answer 28

-backtracking
-visualisation
-data mining
-heuristics
-performance modelling
-pipelining
-divide and conquer

Question 29

Explain backtracking

Answer 29

-problem solving technique implemented using algorithms, often recursively
-methodically builds a solution based on visited pathways found to be correct
-if a pathway is found to be invalid, algorithm backtracks to previous stage

Question 30

Explain data mining

Answer 30

-technique used to identify patterns or outliers in large data sets collected from a variety of sources (also known as big data)
-trends spotted can aids predictions about the future

Question 31

Explain heuristics and give an example of where this may be used

Answer 31

-non-optimal, ‘rule-of-thumb’ approach to problem solving
-used to find an approximate solution when the standard solution takes too long to find
-isn’t perfectly accurate/complete

example: A* pathfinding algorithm

Question 32

Explain performance modelling

Answer 32

-mathematical methods used to test various loads on different OS
-provides cheaper, less time-consuming or safer method of testing applications

Question 33

Explain visualisation

Answer 33

-data can be presented in a way that is easier for us to understand using graphs, trees, charts etc.
-makes it possible to identify trends that were not otherwise obvious