Unit 2

Question 1

What is a data type?

Answer 1

The kind of values that can be used in a data item

Question 2

what is an arithmetic operator?

Answer 2

a symbol that will perform an operation on numbers

Question 3

Examples of data types

Answer 3

• Integer
• Float/Real
• Character
• String
• Boolean

Question 4

Examples of arithmetic operators

Answer 4

+, -, *, /, ^, MOD, DIV

Question 5

what is a range check?

Answer 5

ensuring that a number or date is within a sensible/allowed range

Question 6

what is a type check?

Answer 6

ensuring that data is of the right type, such as integer, letter or text

Question 7

Length check

Answer 7

Text entered is not too long or too short - for example, a password is between 8 and 15 characters

Question 8

Presence check

Answer 8

Checks that data has been entered i.e. the field has not been left blank

Question 9

Format check

Answer 9

Checks that the format of, for example, a postcode or email address is correct

Question 10

Validation vs Verification

Answer 10

• Validation can only check that the data entered is reasonable
• Verification is used to double-check that the data has been typed in correctly

Question 11

Double-entry verification

Answer 11

• A user setting up a new password may be asked to type it in twice
• If the two passwords don’t match, they will be asked to enter the password again
• This is known as double-entry verification

Question 12

Authentication routines and an example

Answer 12

• Are used to make sure a person is who they claim to be
• Commonly, you are asked to enter a user ID and a password
• Once you have the entered user ID, the website looks up your password in the database
• If the user ID cannot be found, an error message is displayed
• You usually get three attempts to get your password and then you are locked out

Question 13

Syntax errors

Answer 13

• A syntax error is one where the code written doesn’t conform to the rules of the language
• The compiler doesn’t know how to translate the program into machine code so will give the programmer a syntax error
• The program cannot be run until all syntax errors are fixed

Question 14

Examples of syntax errors

Answer 14

• missing a symbol
• misspelling a word
• mixing up capitalisation in variable names

Question 15

Logic errors

Answer 15

Logic errors are from a misunderstanding of what the code is doing - the code will still run, but have unexpected outcomes
- using the wrong Boolean statement (e.g. OR instead of AND)
- using the wrong data type
- writing statements in the wrong sequence

Question 16

Trace tables

Answer 16

• Used for tracking the outputs of a program, and the values of each variable used in a program
• They are useful for for finding logical errors

Question 17

What is an array?

Answer 17

• An array is a data structure that allows you to hold many items of data which is referenced by one identifier
• All items of data in the array must be of the same data type
• Has a fixed length

Question 18

What is a record?

Answer 18

A data structure consisting of a number of fields which can all be of different types

Question 19

What is a subroutine?

Answer 19

A small subsection of the whole program that performs a specific, well-defined task

Question 20

Parameter

Answer 20

A piece of data that is passed into a subroutine in order for that subroutine to do its job

Question 21

Calling

Answer 21

A process where an instruction in one part of the code tells another named part of the code to run

Question 22

Modularisation

Answer 22

The process of breaking a program into smaller parts called modules. A subroutine is a type of module.

Question 23

Return

Answer 23

A command in which a subroutine passes a piece of data back to the line of code from which it was called

Question 24

Authentication

Answer 24

The software process of ensuring that the person accessing a system is the person who is supposed to access that system. The following might be used:
- Usernames and passwords
- Memorable information - prompting for something only the real user should know, such as favourite place or the name of a first pet
- Checking that the user is using their usual computer