Algorithms

Question 1

Define algorithm

Answer 1

A set of rules to solve a specific problem

Question 2

Why are algorithms designed with no specific programming language

Answer 2

So that the algorithm can be implemented in whichever programming language the developer chooses to use later

Question 3

Give 3 types of algorithm

Answer 3

Pseudocode
Structured English
Flowcharts

Question 4

What is the difference between a variable and a constant

Answer 4

Variable
Value can change

Constant
Given one value which stays the same throughout a program

Question 5

What are constants used for

Answer 5

Improve readability of code
save having to re-enter values in multiple places

Question 6

Outline 5 ways in which a programmer may make a program easier to understand

Answer 6

• self documenting identifiers;
  Variables, procedures, constants, buttons,
  Code can be followed and reduces need for additional annotation

Annotation-
Comments can be added to record developmental process and logic

Layout-
Indentation to make nesting easier, iteration
Improved quality of software, maintain standards

Constants

Avoid using global variables where possible-

Question 7

Outline the meaning behind a scope and lifetime of variables

Answer 7

Scope
The parts of the program in which the variable can be accessed

Lifetime
The duration of time for which the variable holds the value of the execution of a program

Question 8

Describe the advantages of using subroutines

Answer 8

• makes program easier to understand by splitting into smaller chunks
• easier to test each procedure in isolation before using with the rest

-allows team working

• procedures can be re-used in future programs
• compile procedures and put them in subroutine libraries so they can be called from other programs

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Question 9

What is a parameter

Answer 9

Values that can be sent to a procedure and/or received from a procedure

Question 10

Describe value parameters

Answer 10

Used to pass information into a procedure but don’t receive information

Sending a copy of the parameter to the procedure so any changes made are to the copy and not original

Question 11

Outline 7 validation techniques

Answer 11

Range check- between min and max
Presence check- has been entered
Length check
Type check- correct type
Format check- m/yyy
Lookup check- confirmed
Check-digits- coded numbers for identification

Question 12

Describe verification

Answer 12

Checking to see if the data entered is consistent

Question 13

What is a factorial

Answer 13

Recursion
Factorial(n) = n x Factorial(n-1)

Question 14

State 3 ways to identify a recursion

Answer 14

Calls itself
Has a terminating condition
When it calls itself it passes one or more parameters

Question 15

Outline As and Ds for recursion

Answer 15

Requires less code and therefore more elegant
A natural way of thinking about the program

When it runs, it can use more memory bc it needs to keep track of each of the multiple calls to the procedures
Debugging can be more difficult because when an error occurs, it’s not easy to work out which level the error occurred