Chapter 7: Files & Input

Question 1

Why shouldn’t files be ‘opened’ for too long?

Answer 1

When a file is open, they can easily be corrupted, thus they should be kept open for the shortest time possible.

This is because, if the solution crashes, the file will be corrupted/damaged if the file is open.

Question 2

Why is security required?

Answer 2

As files can contain sensitive user information (usernames & passwords), leaving a file unprotected can be dangerous as someone can access the file DIRECTLY rather than through the solution.

Question 2

What are some security measures to put into place to prevent unauthorised access?

Answer 2

1) Encryption
2) Files can be password protected
3) Files can be placed into folders that are only accessible by the administrator

Question 3

Define archiving

Answer 3

Archiving is simply the process of removing those files that are no longer required to be accessed to another storage medium that can securely store them for a LIMITED period of time.

Question 3

What is involved in performing a backup?

Answer 3

1) Simple as making a copy -> placing it in a secure location

2) The frequency of the backup DEPENDS on
- how much data is there to backup
- facilities available
- how valuable the data is

Question 4

Why is archiving necessary?

Answer 4

Because storage space is LIMITED. It is necessary to remove the files that you no longer need.

Question 5

What are some threats to data?

Answer 5

1) Accidental
2) Event-based
3) Deliberate

Question 5

What is the use of an Uninterrupted Power Supply (UPS)

Answer 5

In the event of a power outage, a UPS can keep a server running for enough time to complete an (up-to-date) backup and for the system to SAFELY SHUTDOWN without damaging any files.

Question 5

What is Version Control Software (VCS)?

Answer 5

Applications that help organisations keep track of their backup versions, which is vital for managing backups.

Question 6

How does a full backup work?

Answer 6

All the Data is copied to the chosen backup media.

Question 7

When should a backup be performed?

Answer 7

Usually at the end of the day. BECAUSE:

-> because the backup can interrupt the procedure

-> it can take a long time to complete, which is why they are generally performed at night

Question 7

Advantage of full backup

Answer 7

A full backup is able to restore the ENTIRE set of data at once.

Question 7

What should you consider when backing up?

Answer 7

The backup media should be able to ACCOMMODATE the size of the backup, without having to swap or change the media in between/during the backup process.

Question 7

Disadvantages of full backup

Answer 7

1) Time consuming if there is a large amount of data to backup

2) Requires a medium (e.g. usb) which can store the combined size of all the files -> EXPENSIVE

Question 8

How does a Differential backup work?

Answer 8

1) A full backup is made
2) Subsequent backups only contain the FILES that have changed

Question 9

Disadvantages of differential backup

Answer 9

1) RESTORING the backup is more complex than restoring a full backup

2) to FULLY RESTORE the backup,
the full backup needs to be restored and also the most recent differential backup

3) When the number of files grow, the size of a differential backup will be too large to handle, and thus will require ANOTHER FULL BACKUP

Question 9

Advantages of differential backup

Answer 9

1) Only 2 backups are made, (the full backup and the most recent differential backup)

2) The process of completing daily backups is more simpler and quick

Question 10

How does an incremental backup work?

Answer 10

1) Full backup is made
2) The Subsequent backups consist of changes to the previous incremental backup.

Question 11

What is the advantage of incremental backup?

Answer 11

The BACKUP process is more efficient

Question 11

What are the disadvantages of using incremental backup?

Answer 11

to RESTORE, it takes longer/is more complicated because the full backup needs to be restored + ALL the incremental backups in order.

Question 12

What does the backup media Cloud Storage involve?

Answer 12

Moving the data to the cloud storage on a regular schedule, or manually, such as Google drive, Onedrive.

Question 13

Advantages of using Cloud Storage of backup media

Answer 13

1) Independent of physical media and only relies on the accessibility of the CLOUD SERVER

2) RETRIEVING the backup just requires you to connect to the cloud server and transferring the required files.

Question 14

Disadvantages of using Cloud Storage

Answer 14

During a power outage, you cannot access the data

Question 15

Advantages of using Tape backup as backup media

Answer 15

1) Holds onto data for a really long time
2) Cheap
3) Portable and small
4) Easy to store compared to other physical media
5) many formats involve encryption

Question 15

Disadvantages of using Tape backup

Answer 15

Time consuming, limited space

Question 16

Advantages of using hard disk as a backup media

Answer 16

1) Performing a backup is quick
2) Large capacity
3) Portable
4) Can be connected to an information system

Question 16

Disadvantages of using a hard disk as a backup media

Answer 16

1) Can be easily damaged
2) Volatility
3) Do not retain data for a long period of time

Question 17

Advantages of using SSD (Solid State Drive)

Answer 17

1) Highly portable
2) Easy to transport
3) Less likely to be physically damaged
4) Speed is relatively good

Question 17

What are the factors you should consider

Answer 17

1) Backups should be easily accessible

2) Despite backups, there will still be a version gap between the data that has been lost and the last backup

3) At least one backup should be kept OFFSITE in the event of a disaster

4) MULTIPLES of backup media should be produced in case a media fails

5) A backup procedure should include a detailed procedure.

Question 18

Advantages and disadvantages of Arrays

Answer 18

Advantages

1) Easy to use
2) Every Language supoorts them

Disadvantages:

1) Array elements need to be of the same type, which is why records can be used

2) The size of an array can make it time consuming to navigate

Question 18

Disadvantages of using SSD (Solid State Drive)

Answer 18

1) Information on their ability to retain data is limited
2) Very expensive
3) Data recovery is difficult if a SSD FAILS

Question 18

What are Data Structures?

Answer 18

The ways that data can be stored to enable efficient algorithms to be used to optimise program execution time.

Question 19

How do arrays work?

Answer 19

A set of data elements under the same name, where they can hold any type of data (SAME TYPE, for instance only strings or only numbers),
Accessed via a index starting from 0

Question 19

What are classes?

Answer 19

Objects that have a number of methods and events associated within it

They can be duplicated as many times as required

You can declare objects within a particular class and it can be referenced on its own

Question 19

What are the advantages/disadvantages of using dictionaries?

Answer 19

Users can access both the key and value, however, only one value is stored per key, which also has to be unique

Question 19

Advantages and disadvantages of classes

Answer 19

1) Useful when a large number of objects needs to be created, or when standard variables would be difficult to use

Shortcoming:
- Can be hard to define initially

Question 20

What is the difference between records and arrays?

Answer 20

Records are structures that can used to group together variables for a particular purpose.

While an array usually contains elements of all the same variable type, the fields within a record may be of different types + sizes.

Question 21

What are stacks and how do they work?

Answer 21

One-dimensional array of values that are accessed in a particular way.

-> Works on the principle First in Last out (FILO)
-> A ‘push’ function adds data to the top of the stack
-> A ‘pop’ function removes data from the top of the stack

THE ELEMENT THAT IS INSERTED FIRST, COMES OUT LAST

Question 22

What are the advantages and disadvantages of using stacks?

Answer 22

As they use FILO, they are useful in executing code and backtracking through “call to functions” once they have been completed.

The disadvantage is that they are limited in size.

Question 23

What are linked lists and how do you create/use them

Answer 23

Data structure that maintains itself in order at all times. (BASICALLY SORTED ARRAYS). The elements are placed in the correct order STRAIGHT AWAY, which is better than using arrays where they are unsorted and you need to use sorting algorithms to sort them in order.

To create a linked list,you need 2 lists:

1) One to store the required information
2) One to store the links which will point to the next array element

Question 24

advantages and disadvantages of using linked lists

Answer 24

Benefits:
1) Very large
2) Elements are added in order

Shortcomings:
1) Maintaining the list can be difficult, but arrays are even harder

Question 25

What are hash tables?

Answer 25

Similar to dictionaries but uses (key, bucket) instead of (key, value) pairs. Is more efficient for searching.