Unit 2.2.1 - Programming Techniques

Question 1

What are the three programming constructs?

Answer 1

• Sequence
• Selection
• Iteration

Question 2

What is sequence?

Answer 2

Instructions in a program are executed in the order they have been written.

Question 3

What is iteration?

Answer 3

It allows sections of code to be repeated.

Question 4

What is selection?

Answer 4

A program that changes direction depending on the outcome of a condition. They are usually shown using Boolean expressions (IF statement).It allows sections of code to be repeated.

Question 5

What are the two types of loops?

Answer 5

• Count - controlled loop (FOR)
• Condition - controlled (DO UNTIL/WHILE)

Question 6

What is a count-controlled loop?

Answer 6

A loop which is used when the required number of iterations is known ahead of execution.

Question 7

What is a condition-controlled loop?

Answer 7

A loop with a condition at the start to determine if the iteration should occur or not. As long as the condition is met the iteration continues.

It is used when the number of required iterations are not known.

Question 8

What is a nested construct?

Answer 8

• A programming construct that is included within another programming construct.
• It enables powerful yet simple programming.
• It reduces the amount of code needed, while making it simple for a programmer to debug and edit

Question 9

What is recursion?

Answer 9

When a subroutine (often a function) calls itself from within its own subroutine.

Question 10

What characteristics should a recursive subroutine exhibit?

Answer 10

• It contains a terminating condition (base case).
• For any input value other than the terminating condition, the subroutine should call itself.
• The base case should be reached within a finite number of times.

Question 11

What would happen if there wasn’t a base case, or the base case cannot be achieved in a finite number of times?

Answer 11

The subroutine would call itself indefinitely, taking up memory and resulting in a stack overflow. This could cause the program to crash.

Question 12

Why is recursion not very efficient?

Answer 12

Every time a recursive function calls itself, the processor must remember the address it must jump back to later and the previous variables by using stacks, which takes up space in memory.

Question 13

When is recursion needed rather than iteration?

Answer 13

• Tree traversal algorithms
• Performing a flood fill in a graphics application

Question 14

What is the scope?

Answer 14

The scope of a variable refers to where it is accessible in the code. The scope is global or local.​

Question 15

What is a local variable?

Answer 15

• Declared inside a subroutine.​
• Only accessible by that subroutine.​
• Created when the subroutine is called.​
• Destroyed when the subroutine ends.​

Question 16

What is a global variable?

Answer 16

• Declared at the top of a program, outside of any subroutine.​
• Accessible throughout the program.​
• Created when the program starts.​
• Destroyed when the program ends.​

Question 17

What are the advantages of local variables?

Answer 17

• Memory efficient
• Avoiding naming conflicts and errors
• Easier to debug

Question 18

What are the disadvantages of local variables?

Answer 18

• Limited scope
• Difficult to reuse/share data between different parts of a program
• More difficult to debug (difficult to identify and fix errors)
• May slow execution

Question 19

What are the advantages of global variables?

Answer 19

• Can be accessed from anywhere in a program
• Can share data between functions
• Stores persistent data
• Accessed from any function

Question 20

What are the disadvantages of global variables?

Answer 20

• Any change in a global variable is propagated throughout the program
• Make the code less modular, flexible and scalable
• Name collisions
• Logic errors by modifying global variable in one function
• Takes up memory space

Question 21

What is a procedure?

Answer 21

A block of code that takes in zero, 1 or more parameters and performs a set task.

Question 22

What is a function?

Answer 22

A block of code that takes in zero, 1 or more parameters; performs a set task and returns a value.

Question 23

What is modularity?

Answer 23

The concept of breaking down a large problem/program into smaller parts.

The goal is to design the program in such a way that each module carries out a single specific task.

Question 24

Why are functions used in modular programming?

Answer 24

• Performs data on input data (parameters) and return a result.
• Can be called numerous times, reducing duplicated code
• Enable larger programs to e written using reusable code
• Stores in libraries for other programmers to use in their programs

Question 25

Why are procedures used in modular programming?

Answer 25

- Used to break a program into manageable sections - Easier to read and debug - Uses local variables - Enables different programmers to work out different parts of the code - Allows routines to be reused in other programs

Question 26

What are the three types of sub routines?

Answer 26

- Methods - Functions - Procedures

Question 27

Why are library functions used in modular programming?

Answer 27

- They are already tested - Make use of other programmers' expertise - Can be written in other languages as they're already compiled

Question 28

What does the interface (first line) of a subroutine specify?

Answer 28

- Name of subroutine - List of parameters required when it's called - Order of parameters - Data type for these parameters

Question 29

What is Object Oriented Programming (OOP)?

Answer 29

A paradigm, involving the attempt to capture or group information, data and related functionality into structure items known as objects.​

Question 30

What is an IDE (Integrated Development Environment)?

Answer 30

A software application that provides a set of tools and related functionality to maximise the programmer's productivity. It is designed to allow the programmer to modify, compile and debug their program.

Question 31

What are the common features of an IDE?

Answer 31

- Code editors​ - Error diagnostics​ - Runtime environments​ - Translators​ - Auto-documentation​ - Syntax highlighting​ - Autocompletion​

Question 32

What is a class?

Answer 32

A template for creating objects. It defines the attributes and behaviours that the instantiated objects will have. Classes act as user-defined data types in OOP.

Question 33

What is an object?

Answer 33

An instance of a class which represents a real-world entity, combining data (attributes) and the actions (methods) that can be performed on that data.

Question 34

What is an attribute?

Answer 34

A specific item of data for a class/object.

Question 35

What is a method?

Answer 35

A subroutine defined within a class.

Question 36

What is a Private method?

Answer 36

An access modifier which can only be accessed within the class.

Question 36

What is encapsulation?

Answer 36

Data held within a class (attributes) that can only be accessed via its methods. They cannot be accessed directly, thus promoting data hiding and the principle of information hiding.

Question 37

What is a Public method?

Answer 37

An access modifier which can be accessed anywhere from the scope of the class.

Question 38

What is Instantiation?

Answer 38

The process of creating an instance (object) of a class. It involves allocating memory and initializing the object based on the structure and behaviour defined by the class.

Question 39

What is Inheritance?

Answer 39

A mechanism that allows a new class (subclass or derived class) to inherit attributes and behaviours from an existing class (base class) and add further functionality to it. It promotes code reuse and the creation of a hierarchy of classes.

Question 40

What is a Base (Super) Class?

Answer 40

The class from which a subclass inherits its attributes and behaviours. It is higher in the class hierarchy and provides a common set of features that multiple subclasses can share.

Question 41

What is abstraction (in OOP)?

Answer 41

The ability to represent a real-world object as a simplified representation in code.

Question 42

What is a constructor?

Answer 42

A special method which creates an object from a class.

Question 43

What is Overloading?

Answer 43

The ability for different methods to have the same names but different number of parameters which therefore exhibit different behaviours.

Question 44

What is Polymorphism?

Answer 44

The ability for methods of the same name to be used in inherited classes with different behaviours exhibited.

Question 45

What is the purpose of a code editor in an IDE?

Answer 45

- A text area for programmers to enter code directly into the IDE - Often supports additional features like syntax highlighting, autocomplete and automatic indentation

Question 46

What is the purpose of error diagnostics in an IDE?

Answer 46

- Reports errors (mainly syntax) in the code and where they can be found - Often suggests possible fixes

Question 47

What is the purpose of a run-time environments in an IDE?

Answer 47

- Software that supports the execution and running of programs - Allows programmers to easily run code during development

Question 48

What is the purpose of translators in an IDE?

Answer 48

A program that converts high-level code into executable machine code.​

Question 49

What is the purpose of auto-documentation in an IDE?

Answer 49

Tracks variables declared by the programmer, modules and other special programmer comments with a view to producing documentation that aids in program maintenance, debugging and support.​

Question 50

What does it mean to 'Pass by value'?

Answer 50

- When a function is called, a copy of the actual parameter’s value is passed to the function - The original parameter remains unchanged outside the function - Suitable when you only need to use the parameter for computation within the function without altering it for the client program

Question 51

What does it mean to 'Pass by reference (address)'?

Answer 51

- A copy of the address (reference) of the actual parameter is stored - Any changes made to the parameter within the function directly affect the original parameter outside the function - Used when you intend to modify the parameter passed in by the client program