2.2.1 Programming Techniques

Question 1

What is a variable?

Answer 1

• Identifier of a memory location used to store data
• Used to store a value which can change during execution

Question 2

What are the global variables?

Answer 2

• The variable can be accessed throughout the scope of the program (visible throughout a program)
• Using passing by reference is an equivalent of a global variable.

Question 3

What are the negatives of global variables?

Answer 3

• Uses more memory - memory is declared when the program starts and remains in use throughout.
• Testing more difficult - it is difficult to test an individual block of code.
• Reduces data accuracy - Changing a global variable may have an impact on another module.

Question 4

What are the positives of global variables?

Answer 4

• Simpler to program - values do not need to be passed between different subroutines.
• Do not need to worry about returning values - all parts of the program can access the value.

Question 5

What is a local variable?

Answer 5

Can only be accessed within the scope of the sub-program where it is created

A parameter that is passed into a subroutine becomes a local variable in the subroutine e.g. LoadLevel(Difficulty)

Question 6

What is an IDE?

Answer 6

Integrated Development Environment (IDE) - A program used for developing programs, made from several components.

Question 7

What tools are provided by an IDE to develop software?

Answer 7

• Auto-complete – Will predict variable and built-in functions and finish off the word. Can avoid spelling mistakes and speed up development
• Syntax highlighting (colour coding text) - Can distinguish between different features quickly to check code is correct
• Auto Indent – Indents code automatically within structures to avoid errors

Question 8

What tools are provided by an IDE to debug software?

Answer 8

• Error highlighting - Syntax errors highlight dynamically so they can be corrected before running the program (saving time)
• Variable Watch window – Display the values of the variables during running of the program
• Break points- Stop the program at set points to check the values of variables. Developer can add multiple breakpoints.
• Error message list- Tells you where errors are and suggests corrections
• Stepping - Executes program one line at a time to watch variable values and program pathways
• Traces - Printouts of variable values for each statement execution

Question 9

What are the three programming constructs?

Answer 9

• Sequence
• Selection / Branching
• Iteration

Question 10

What is an example of a count controlled loop?

Answer 10

FOR Loop - Will run for a set number of predetermined times.

Question 11

What is an example of a condition controlled loop?

Answer 11

WHILE / DO WHILE - Will run whilst a condition is true or false

Question 12

What are parameters?

Answer 12

Parameters are the variables listed between the brackets, after the procedure/function name e.g.

They become local variables in the routines that they are passed to.

characterMovement(inputKey, characterx, charactery)

Question 13

What does passing by value mean?

Answer 13

By Value (ByVal)
* Does not override the original data
* A local copy of the data is used
* Data is discarded when the subprogram exits

Question 14

What does passing by reference mean?

Answer 14

By Reference (ByRef)
* Changes are made to the original data
* Memory location of data is sent
* Changes remain after the subprogram exits
* Uses less memory

Question 15

What is a function?

Answer 15

• A named block of code which always returns a value
• Uses the keyword return
• Assigns the returned value to a variable (e.g. y)

Question 16

What is a procedure?

Answer 16

• A named block of code which does not return a value
• Does not use the keyword return
• Is called by writing its name but not assigning the result to a variable

Question 17

What are the benefits of modularity in coding?

Answer 17

Breaking code down into functions / procedures / scripts

• Write once and call repeated times - Avoids repeated code.
• Can be tested individually and then added to the main program.
• Can be reused in other programs - No need to reprogram so saves time
• Can give sub-routines to different programmers to build concurrently
• Breaks problems into smaller areas. Small sub-programs are easier to read / understand / modify