Week 5 - Complex Data Types & Memory

Question 1

What is a primitive data type?

Answer 1

The basic types of data which come default with the programming language.

Eg: boolean, float/real, int, string etc.

Question 2

What’s the difference between an array and a class/record?

Answer 2

A class/record is used to define the blueprint of a general things. This doesn’t contain any actual values.

However, an array is used for storing multiple variables and values.

Question 3

Pass by Value

Answer 3

Takes a copy of the variable and passes it to the called function or procedure.
Passes only the value of the variable.

Like downloading Word Doc to edit on your own. Changes made are independent of the main doc.

Question 4

Pass by Reference

Answer 4

Takes a copy of the link to the content passes it to the called function or procedure.
Passes the actual variable and value.

Like emailing a link to a Google Docs which allows for everyone to make changes to the main document.

Question 5

What are the main parts of memory?

Answer 5

The code area, global variables, the stack and the heap.

Question 6

What are pointers and references used for?

Answer 6

Pointers/references are found on the stack, and link to a value or variable on the heap.

Question 7

Can you assign values to fields once you define a type?

Answer 7

No. Because you need to first initialise the values.

This is where you have the placeholder values, so that you can then pass values into that class/function.

Question 8

What are the main ways of using complex and custom data types in Ruby?

Answer 8

Classes/records, structs & modules/enumerations.

Question 9

The Stack

Answer 9

A part of the computer memory responsible for storing function calls and local variables.

Question 10

The Heap

Answer 10

It’s a large pool of memory where the running program can request chunks of memory.
This is typically used alongside pointers and references on the stack to point to memory on the heap.

This is typically called dynamic allocation.

Question 11

Code Area

Answer 11

Where class definitions go and main code goes.

This area of memory is fixed.

Question 12

Global Variables

Answer 12

Where all global variables and constants accessible to all functions are stored in the computer memory.

This area of memory is fixed.

Question 13

What’s the difference between the stack and the heap?

Answer 13

The stack is a linear data structure, whereas the heap is a hierarchical data structure.

The stack is fixed, whereas the heap is dynamic and can change throughout the runtime of a program.

Question 14

Enumerations

Answer 14

Modules define an enumeration which is a custom data type.

They are not not like classes or structs because they are created as a set of constants.

Question 15

Attributes

Answer 15

Used to define data/special characteristics of a class/record. They make up the blueprint of our class.

Question 16

Methods

Answer 16

Functions/procedures used to handle the behaviour.

Question 17

Instance/Object

Answer 17

Is a concrete occurrence of any object. This is the same thing as a token.

Eg: a program may have a class/object named Animal, but there could be many instances of Animal, such as lion, cat, and dog.

Question 18

What’s the difference between instance and class?

Answer 18

Class is the blueprint for an object, whereas the instance is a specific token of that class.

If our class is animals, then an instance could be dog.

Question 19

How do we access enumerations?

Answer 19

Access by using ‘Class name here’::’value’

Question 20

How do we add values onto the end of an array?

Answer 20

Use: Array &laquo_space;value

Question 21

Stack Overflow

Answer 21

Occurs when the space on the stack has exceeded and the operating system will stop and complain to fix this issue.

Question 22

What does .new() do?

Answer 22

Allows for a programmer to allocate memory on the heap.

Question 23

Objects

Answer 23

An abstraction used to represent objects in the real world such as cars, birds, trees etc.

Objects have 2 features which are data & behaviour.

Eg: colour, name, speed
Eg: drive, stop, accelerate

Question 24

Why do we need to use the heap?

Answer 24

It allows for programmers to have more control over the computer memory being used.

Question 25

What’s the difference between a pointer and a reference?

Answer 25

A pointer has the freedom to be assigned to the location of a variable.

References are directly put onto a variable, meaning that you can now call the variable two ways, by the variable name or the reference name.