Fundamentals of programming

Question 1

What is the && operator?

Answer 1

Called Logical AND operator. If both the operands are non zero then condition becomes true.

e.g. (A && B) is false.

Question 2

What is the || operator?

Answer 2

Called Logical OR Operator. If any of the two operands is non zero then condition becomes true.

e.g. (A || B) is true.

Question 3

What is the ! operator?

Answer 3

Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false.

!(A && B) is true.

Question 4

What is the difference between the For, While and Do While loop? When should you use each?

Answer 4

While Loop:
- Used when you know you need to loop
- But don’t know how many times
- Remember checks condition first
- So may never run if condition not met at the start
- Need additional variables to control or count

For Loop:
- Use when you know how many times to run
- Or you can work out how many times
- Good for traversing a table or structure
- The variable declared can be used in the code

Do While
- Used when you don’t know how many times
- But you do know it is at least once
- Need additional variables to control or count

Question 5

How do you change between Upper and Lower case?

Answer 5

string word = “crystal”;
Console.WriteLine(word.ToUpper());
Console.WriteLine(word.ToLower());
output=
CRYSTAL
crystal

Question 6

How do you create a substring from a string?

Answer 6

string word = “crystal”;

Console.WriteLine(word.Substring(3, 3));
Console.WriteLine(word.Substring(1, 4));
//first number is index, second is length

output=
STA
RYST

Question 7

How do you find the index of something within a string? How do you check if a string is contained within another?

Answer 7

string word = “crystal”;

Console.WriteLine(word.IndexOf(“sta”));
Console.WriteLine(word.Contains(“cry”));

output=
3
TRUE

Question 8

How do you insert one string into another?

Answer 8

word.Insert(index, “”)

Question 9

What are the Math operations?

Answer 9

Math.Abs - returns the absolute value
Math.Truncate - cut off any fractional part e.g. 14.56 -> 14
Math.Round - round to nearest whole number
Math.Floor - round down
Math.Pow - raise a number to the power of
Math.Sqrt - returns the squre root

Question 10

What is a function?

Answer 10

A subroutine that returns a value

Question 11

How does passing parameters into a function work?

Answer 11

• Subroutines can accept variables
  1. Data types must be specified within brackets, 2. The same order of specifying variables must be used when calling the function

Question 12

What does reference (ref) do for a value in a subroutine?

Answer 12

Any changes made to the value within the subroutine are retained, without this, they are not.

Question 13

What is one benefit of using reference?

Answer 13

It removes the need for global variables

Question 14

What is an exception?

Answer 14

An exception is an event, which occurs during the execution of a program, that disrupts the normal flow of the program’s instructions

Question 15

How does try, catch work?

Answer 15

• If an exception occurs, instead of erroring, the code at risk of causing an error can be wrapped in a ‘try{}’, if it does cause an exception the ‘catch{}’ block will be run.
• If no exception occurs, the catch block is ignored

Question 16

What is a base case?

Answer 16

• Any recursive subroutine must meet have a stopping
  condition (called a base case) which must be met at some
  point in the execution of the program.

Question 17

What is a Local Variable?

Answer 17

• A local variable is a variable that can only be accessed from the subroutine within which it is declared.
• They only exist in the computer’s memory when their parent subroutine is
  executing.
• More memory efficient way of storing data than using global variables,

Question 18

What is a Global Variable?

Answer 18

• Can be accessed from any part of a program
• Exists in memory for the entire duration of the program’s execution.
• Local variables can be given the same identifier name as global variables -
  generally considered bad practice.
• When the local variable’s value is changed, the global
  variable’s value remains the same.

Question 19

What is Object Oriented Programming?

Answer 19

A programming paradigm based on objects:
Object: An instance of a class
Class: Blueprint/template for an object

Question 20

What does an object contain?

Answer 20

• Attributes (properties) e.g. size, shape, colour
• Methods (actions) e.g. changeSize(), changeShape(), changeColour()

Question 21

What is an object defined as?

Answer 21

An instance of a class, contains both attributes and methods

Question 22

What is a class defined as?

Answer 22

A template for creation of objects, an object is built from a class and you can have many instances of the same class

Question 23

What is a Method defined as?

Answer 23

• A program routine within an object
• Carries out a particular task on an object
• Can be inherited from a superclass (Parent)

Question 24

What is procedural programming?

Answer 24

Where programs are formed from sequences of instructions which are executed in the order in which they appear.

Question 25

What are some problems with procedural programming?

list 2

Answer 25

Data and procedures that operate on said data are kept separate, therefore:

• Relationships between data item and code operating on it may not always seem obvious
• Errors would be difficult to find

Question 26

What is inheritance defined as?

Answer 26

Inheritance is where a child class takes on attributes and methods from a parent class, it is efficient as code can be re used and organised

Question 27

What is encapsulation defined as?

Answer 27

The process of packaging an objects data together with its new methods. It is a hidden technical implementation within the object. They cannot be directly other objects
Uses public (+), private(-) and protected(#) access modifiers

Question 28

Benefits of encapsulation?

Answer 28

• Prevents users from gaining access to certain data
• Any modifications to the internal code will not cause problems elsewhere, object can be maintained independently

Question 29

What is Polymorphism? What can it be used for?

Answer 29

Polymorphism allows many similar versions of a method (with the same name)
It can be used to:

• Provide several versions of a method in once class, with different parameters
• Override a method inherited from a parent class

Question 30

How would you define Composition?

Answer 30

• Creating an object containing other objects, that will cease to exist if the containing object is destroyed
• e.g. Workforce contains manager, employee – manager and employee will cease to exist if workforce is destroyed
• filled diamond defines composition

Question 31

How would you define Aggregation?

Answer 31

• Creating an object that would contain other objects, but the objects will continue to exist even if the containing object is destroyed
• e.g. House has parent and children contained within, but if House is destroyed, parent and children continue to exist
• empty diamond defines aggregation

Question 32

What is a ‘Static’ method?

Answer 32

• Static means the method can be used without creating an instance, as it does not change

Question 33

What is a ‘Virtual’ method?

Answer 33

• Virtual means the method is defined in the base class, but can be overriden by a method in the subclass

Question 34

What is an ‘Abstract’ method?

Answer 34

• The actual method is not supplied by the base class, and must be provided by the sub class. The object is used as an interface between the method and the data.