2.1 Algorithm Design

Question 1

Describe the purpose of validation

Answer 1

To test whether the data entered is reasonable/sensible.

Question 2

State 5 types of validation check

Answer 2

Range check
Type check
Length check
Presence Check
Character check

+ Format check
+ Look up check

Question 3

Describe a length check and give an example

Answer 3

Checks whether the data entered is within a certain number of characters

e.g. Passwords often have a minimum and maximum number of characters

Question 4

Describe a range check and give an example

Answer 4

Checks whether the values entered are within a certain range

e.g. exam percentage must be between 0 and 100

Question 5

Describe a presence check and give an example

Answer 5

Checks that some data has been entered (not left blank)

e.g. you must enter a username when setting up an account

Question 6

Describe a type check and give an example

Answer 6

Check that the correct type of data has been entered

e.g. you must enter an integer when inputting an age

Question 7

Describe a format check and give an example

Answer 7

Check that an appropriate format of letters and numbers has been used

e.g. Date must be in the format DD/MM/YYYY

Question 8

Describe a character check and give an example

Answer 8

Checks that the input contains (or does not contain) specific characters

e.g. Passwords must contain uppercase, lowercase characters and digits

Question 9

Describe the purpose of verification

Answer 9

To check that the data input is the same as the original source (intended input)

Question 10

Describe 2 types of verification

Answer 10

Double Entry - Expects data to be entered twice and compares both entries to check if they are the same.

Visual Check - Data is entered once and then visually compared against the original (or entered value)

Question 11

State 4 different types of test data

Answer 11

Normal (valid)
Abnormal (invalid)
Extreme
Boundary

Question 12

Describe normal/valid test data

Answer 12

Data that should be accepted and has known outcomes

Question 13

Describe abnormal/invalid test data

Answer 13

Data that should be rejected and produce error messages

Question 14

Describe extreme test data

Answer 14

The largest and smallest values that would be accepted

Question 15

Describe boundary test data

Answer 15

Is used to establish where the largest and smallest values occur.
At each boundary 2 values are required: one valid and one invalid

Question 16

A user is asked to enter a valid percentage. It must be a positive whole number between 0 and 100 inclusive.

State 4 different types of test data and for each one give an example of one piece of appropriate data along with a reason

Answer 16

Normal … 23 … the value is within normal range and should be accepted
Abnormal … 3.3 … the value is an invalid data type and should be rejected
Extreme … 100 … the value is the largest value that should be accepted
Boundary … 101 … tests the invalid value at the highest boundary and should be rejected

Question 17

What is an algorithm?

Answer 17

A set of step-by-step instructions to solve a problem of complete a task
It is independent of any programming language
Can be expressed using pseudocode or a flowchart

Question 18

What are the names and shapes of the 5 flowchart symbols you need to know?

Answer 18

Question 19

Convert to a flowchart

Answer 19

Question 20

Convert to a flowchart

Answer 20

Question 21

Convert to a flowchart

Answer 21

Question 22

Convert to a flowchart

Answer 22

Question 23

Convert to a flowchart

Answer 23

Question 24

Convert to a flowchart

Answer 24

Question 25

Convert to a flowchart

Answer 25

Question 26

Convert to a flowchart

Answer 26

Question 27

What is a structure chart?

Answer 27

• A modelling tool used to show the hierarchy of a system/program
• A graphical representation to show how a system is broken into subsystems

Question 28

What are library routines?

Answer 28

A collection of standard programs/routines availaible for immediate use

Question 29

What is a subroutine?

Answer 29

• A self-contained piece of code that that is given a name and can called from within a program
• 2 types of subroutines
  
  • A function - always returns a value
  • A procedure - may or may not return a value

Question 30

What is a procedure?

Answer 30

A subroutine that does not have to return a value

Question 31

What is a function?

Answer 31

A subroutine that always returns a value

Question 32

Describe the use of a subroutine in a program

Answer 32

• It is a block of code within a program that can be called when needed
• It breaks up the program to make it easier to read and understand
• It can be reused by another program

Question 33

What is a library routine?

Answer 33

• A standard subroutine that is available for immediate use
• It can be called from many programs
• It is used often and makes programs easier/faster to write as the code is already written
• They make testing easier as they have already been used and debugged

Question 34

What is top down design?

Answer 34

Breaks down a system into successively smaller pieces/sub systems

Question 35

What are the benefits of top down design?

Answer 35

• allows several programmers to work at the same time on the software
• Development time is faster
• can test each subsystem independently
• Easier to debug