Unit 1 Review

Which of the following best describe examples of abstraction

• A developer writing a program for calculating properties of shapes uses a variable pi to store a decimal approximation of the number π (~3.14159). They use this variable whenever they need to use the number π to calculate an area or volume.

• A series of steps for creating a model aeroplane is laid out in a clear order, with specific instructions in great detail for completing each step.

• Several developers are working on a program together. In order to complete the work efficiently, they split the program up into several parts, and each work on a section, testing as they proceed. When code is complete they add it to a master program.

Answer explanation

This is correct. The constant π, which has an infinite decimal expansion, is represented by a simple variable name of pi. This is therefore an example of abstraction, where a complex system is replaced with a simplified representation.

Rick is in charge of a team developing a program which will be used by businesses to control stock. The team has already consulted with potential clients and developed an idea of what inputs will be required and the likely outputs that will be produced from these inputs. Which of the following should Rick and his team do next?

Correct Answer

• Write segments of code in different languages to see which language will be most suitable for the job

• Plan the structure of the program and determine how the major algorithms will work

• Make a list of bugs which will occur during development and propose ways these could be fixed

• Decide on the schedule for updates and maintenance of the code

Answer explanation

This is correct. When the initial planning and ideas phase of the development cycle is complete, the next step should be to consider the overall design of the program and how it will implement the desired functionality.

Jama is creating a program which calculates the square roots of whole numbers. The program will store the results of each square-root as a variable. Which of the following data-types would be best used for this variable?

• int

• string

• bool

• float

Answer explanation

This is correct. The square root of an integer may be another integer or a non-integer number (e.g. the square root of 2 is 1.4142…). Since the floating point number (float) data type stores decimal numbers, this makes it an ideal data-type for this variable.

Which of the following describes algorithmic solutions to problems:

I. A set of step by step instructions for assembling a piece of furniture.

II. A flowchart used to make important decisions on which actions to take in an emergency situation

III. A recipe for baking a cake with detailed numbered steps to follow

• I, II and III

• I and III only

• I and II only

• II and III only

Answer explanation

This is correct. Each of the problems described (assembling a piece of furniture, dealing with an emergency situation and baking a cake) are solved through a set of logically ordered, precise instructions. These solutions can therefore be thought of as being algorithmic in nature.

Which of the following statements about variables in programming are true?

I. Variables allow a value to be stored for future use

II. Once the value of a variable is set it cannot be changed

III. The name given to a variable is important for human comprehension, but not for the computer.

• II only

• I and III only

• I only

• I, II and III

Answer explanation

This is correct. The use of a variable is primarily to store values which can be used later. It is important to name variables so that code is comprehensible to people reading it (including the original programmer) and its purpose and function can be quickly determined. Despite this, it makes no difference to the running of the program by the computer what variable names are used.

Erin has written a program which presents a user with multiple-choice quiz questions to answer and calculates a percent score based on the number the user got right or wrong. Each question has 5 possible answers, and scores presented are from 0 to 100 percent inclusive. Which of the following could be represented by a boolean variable?

• The correct answer choice for a particular question.

• The percent score of the user

• Whether a user got a specific question right or not

• The number of questions in the quiz.

Answer explanation

This is correct. A boolean variable can have two possible values - true or false. This makes ideal for determining if a user got an individual question right (true) or not (false).

Which of the following statements are NOT true about high level programming languages? Select one answer:

• Code written using high level languages is relatively easy for humans to read, write and parse

• Code written using high level languages usually requires compiling before it can be run

• Code written using high level languages is guaranteed to be ambiguous

Answer explanation

This is correct. This is a false statement as programming languages are unambiguous (when properly documented), meaning a program only has one possible way of being interpreted.

The following algorithm is presented for assembling a piece of furniture from 12 individually numbered parts.

Parts 1, 5, and 11

Parts 2 and 10

Part 12

Parts 6 to 9 inclusive

Parts 3 and 4

Which of the following correctly describe issues with the way these instructions are presented?

I. There instructions lack the required descriptive qualifiers

II. The instructions lack the required imperative statements

III. The order in which the instructions should be performed is unclear

• II only

• I and II

• I only

• I, II and III

Answer explanation

This is correct. The order of instructions is clear, as is which parts should be used for each instruction. Imperative statements (e.g. attach, place together, fasten to) however are required in order for someone following the algorithm to understand what actions they actually have to perform with the parts listed.

Which of the following variable types is characterized by allowing only two possible values to be stored?

• String

• Float

• Boolean

• Array

Answer explanation

This is correct. A boolean can take a true or false value, so is useful for storing variables which can only take 2 possible values.

Marta is writing a program for a home-automation system.

Three of the variables in her program are as follows:

light - A variable which determines whether the lights in a room are switched on or off

temp - A variable which records the temperature of the room to the nearest whole degree Fahrenheit

name - A variable which records the name the user has set for the room (e.g. “kitchen”)

Which of the following correctly describes the types which would be best used for each of these variables?

• light - boolean, temp - integer, name - string

• light - integer, temp - boolean, name - string

• light - string, temp - integer, name - boolean

• light - boolean, temp - string, name - integer

Answer explanation

This is correct. A boolean should be used for light as it can only have two possible value (on/off or true/false). An integer should be used for temp, as it can take many different possible values which are whole numbers. A string should be used for name since it can contain a combination of letters (and/or numbers).