U2b - Programming techniques

Question 1

Examples of subroutines

Answer 1

Functions, procedures

Question 2

What’s the difference between a function and a procedure?

Answer 2

Procedures execute code in a subroutine but they don’t return anything. Functions will return a value after processing has taken place e.g. input returns what the user typed in, random returns a number

Question 3

Define parameters

Answer 3

Values that you can pass through a subroutine

Question 4

Advantages of subroutines (4)

Answer 4

• Each subroutine can be tested separately to make sure it works correctly
• Many programmers can work on a large program at the same time which cuts down development time
• Subroutines can be re-used in other programs
• Program maintenance is easier - if you make a mistake, then you only have to modify the subroutines affected

Question 5

Difference between global and local variables

Answer 5

Global variables are outside of the subroutine, whereas local variables can only be seen and used inside the subroutine

Question 6

What are global variables?

Answer 6

Variables that are accessible anywhere in the program. They’re written in pseudocode using the global keyword

Question 7

What are local variables?

Answer 7

Variables that only exist while the subroutine is executing. They are only accessible within the subroutine.

Question 8

Advantage of using local variables

Answer 8

They keep a subroutine self-contained, so they can be used in any program without variable names conflicting with those used in the calling program

Question 9

Advantages of using structured programming techniques (2)

Answer 9

• The modularised approach of using subroutines breaks down programs into manageable chunks of code, and this helps to decompose larger problems
• By using structured programming techniques, programs will have fewer bugs and be easier to maintain

Question 10

Define scope

Answer 10

The area of a program where an item is recognised

Question 11

Define subroutine

Answer 11

A selection of code that can be grouped together under a name, and then called later in the program

Question 12

Define data validation

Answer 12

Routines that ensure that data entered is of the right type

Question 13

Define range check

Answer 13

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

Question 14

Define type check

Answer 14

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

Question 15

Define length check

Answer 15

Ensures that text entered is not too long or too short e.g. a password between 8 and 15 characters

Question 16

Define presence check

Answer 16

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

Question 17

Define format check

Answer 17

Ensures that the format of something is correct e.g. DD/MM/YY and not MM/DD/YYYY

Question 18

What’s the difference between validation and verification

Answer 18

Validation can only check that the data entered is reasonable, but verification checks that the data entered is correct

Question 19

Give an example of double-entry verification

Answer 19

A user setting a new password being asked to type it in twice. If the two passwords don’t match, they will be asked to enter the password again

Question 20

Define authentication

Answer 20

A routine used to make sure a person is who they claim to be e.g. username and password

Question 21

Ways to make code easier to understand and maintain (5)

Answer 21

• Write comments at the top to show who wrote the program and when they wrote it
• Comments to explain what harder parts of the code do
• Each subroutine should have comments to explain their functionality
• Using meaningful identifiers
• Using a modular structure

Question 22

Why is a trace table useful (3)

Answer 22

• For determining the purpose of an algorithm
• For finding the output of an algorithm
• For finding errors in an algorithm

Question 23

Define syntax error

Answer 23

An error where the code written doesn’t conform to the rules of the language. The program cannot be run until all syntax errors are fixed

Question 24

Define logical error

Answer 24

An error where the program will run, but it won’t work as the programmer intended

Question 25

Examples of test data

Answer 25

Normal, boundary and erroneous