Algorithms 2.1 Flowcharts, Pseudocode, structure diagrams

Question 1

Define flowchart

Answer 1

A flowchart is a method of representing the sequences of steps in an algorithm in the form of a diagram

Question 2

State the different symbols that make up a flowchart and draw what they look like

Answer 2

Terminal
Process
Decision
Input/Output
Sub routine
Line

Question 3

What does the Terminal symbol in a flowchart represent

Answer 3

Terminal symbol – represents the start of end of a process

Question 4

What does the Process symbol in a flowchart represent

Answer 4

Process symbol – represents something being initialized, processed or calculated.

Question 5

What does the Decision symbol in a flowchart represent

Answer 5

Decision symbol – represents the decision. It will have a yes or no, true or false outcomes which will be represented by two separate lines or paths exiting the shape.

Question 6

What does the Input/Output symbol in a flowchart represent

Answer 6

Input/Output symbol – represents the input and output of data to the algorithm

Question 7

What does the Sub routing symbol in a flowchart represent

Answer 7

Sub routing symbol – representing a call to a sub routine. A sub routine will have its own flowchart, but when you call it from the main program, you need to express that call using this symbol

Question 8

What does the Line symbol in a flowchart represent

Answer 8

Line (with an arrow) - represents the control passing between connected shapes. It is the flow of the algorithm

Question 9

Define pseudocode

Answer 9

Pseudocode is an alternative, text-based way of representing the sequence of steps in an algorithm

Question 10

What does the prefix, pseudo mean

Answer 10

The prefix ‘pseudo’ means false or not genuine

Question 11

State an advantage of pseudocode

Answer 11

Pseudocode allows us to lay down the logic of a problem in an almost-like-real-code way without worrying about the actual rules and syntax of a particular language

Question 12

Create a flowchart asking the user to input two numbers, and display to the screen the larger number

Answer 12

file:///C:/Users/44748/Documents/flowcharts%20and%20pseudocode.pdf

Question 13

Create an algorithm in pseudocode, equivalent to the flowchart
file:///C:/Users/44748/Documents/flowcharts%20and%20pseudocode.pdf

Answer 13

number1 = INPUT ()
number2 = INPUT ()

if number 1 > number 2 then
print(“The largest number is” + number1)
else
print(“The largest number is” + number2)
endif

Question 14

When refining an algorithm what do you need to do

Answer 14

Step 1) Identify the areas of existing algorithm which need modifying

Question 15

QUESTION: Refine this algorithm to output the largest of the three numbers entered by the user.

file:///C:/Users/44748/Documents/flowcharts%20and%20pseudocode.pdf

Answer 15

file:///C:/Users/44748/Documents/flowcharts%20and%20pseudocode.pdf

Question 16

Create a flowchart which calculates how much carbon to dose into a fish tank to keep nitrate levels safe. If the nitrate level is above 10 dose 3ml of carbon. If the nitrate level is above 2.5 and smaller than 10 dose 2ml, if the nitrate level is above 1 but smaller than 2.5 dose 1ml is the nitrate level is below 1, dose 0.5ml

Answer 16

file:///C:/Users/44748/Documents/flowcharts%20and%20pseudocode.pdf

Question 17

Create an algorithm in pseudocode, equivalent to the flowchart

Answer 17

file:///C:/Users/44748/Documents/flowcharts%20and%20pseudocode.pdf

Question 18

Describe the pseudocode/flow char fish algorithm
file:///C:/Users/44748/Documents/flowcharts%20and%20pseudocode.pdf

Answer 18

This is a comment to explain the purpose of the program
The user is asked to enter the nitrate level, this value is stored in the variable:nitrate
If nitrate is greater than 10 then Then does 3ml
Otherwise if nitrate is greater than 2.5, Dose 2ml
Otherwise if nitrate is greater than 1 Dose 1ml
Otherwise dose 0.5ml

Question 19

What does 6 MOD 2 mean

Answer 19

6/2 = 3, there is no remainder, therefore the modulus of 6 MOD 2 would equal 0

Question 20

What does 7 DIV 2 mean

Answer 20

DIV – Quotient (integer division) e.g. 7 DIV 2 = 3. It disregards any decimal places that are a result of the division.

Question 21

What is the method, Structure diagrams are produced by called?

Answer 21

Structure diagrams are produced using a method known as step-wise refinement

Question 22

Describe step-wise refinement

Answer 22

We break the problem down using decomposition into smaller and smaller components

Some areas of the program will need breaking down more than others

The lowest level nodes should achieve a single task

These can be then be coded as a single module or sub-program

Question 23

What do structure diagrams look like

Answer 23

file:///C:/Users/44748/Documents/structure%20diagram.pdf