questions on paper 1 Flashcards
(94 cards)
1
Q
Boolean algebra - Order of precidence
A
Brackets
Not
And, Nand
Or, Nor, Xor
2
Q
Defence against malware
A
High code quality Code reviews Patching Penetration testing Network forensics Network policies and user access levels Anti-malware software Firewalls Passwords Encryption Educating users in best practices
3
Q
Code quality
A
Poorly written code
- might leave data in memory to be stolen later
- or contain debugging code that exposes sensitive info
- might contain faulty memory handling e.g. buffer overflow
4
Q
Code reviews
A
Test thoroughly
Explore all possible code branches and input values
- Not all bugs can be found via routine testing
Programmers review each others code
5
Q
Patching
A
Needs to be done regularly
Open source communities release updates or patches to fix bugs all the time
6
Q
Penetration testing
A
aka ethical hacking
Hackers who work with good intent, attempt to break into a network to identify possible security breaches
- Flaws found can then be fixed
7
Q
Network forensics
A
Analysing the packets being transmitted on a network to find out:
- where the hack came from
- how they achieved it
- what data they may have stolen
During or after attack
Can also be used to try to identify any unusual patterns that might indicate that the network is being hacked
8
Q
Network policies and user access levels
A
NPs = rules/settings that are controlled by the network administrator
Control:
- who can access network
- which files/services they can access
- what type of access they have
Prevents unauthorised access
Staff should have agreed to network access policy
9
Q
Anti-malware software
A
Detects and removes malware
- can have a real time checker that scans the files before they are used
- can have schedules scans to perform checks on a regular basis
Must be kept up to date via software updates
10
Q
Firewalls
A
Monitors traffic in and out of a network
- can allow or block data entering or leaving the network
11
Q
Passwords
A
- complex passwords are harder to guess
- dont use a password for more than one account
12
Q
Authenication
A
Proving a user is who they say they are
13
Q
Encryption
A
Data scrambled using an encryption algorithm and a key
- makes data unreadable
- complex keys prevent brute force attacks
- prevents eavesdropping
14
Q
Phishing
A
attempting to fraudulently gain info from someone
15
Q
Malware
A
Malicious software aims: - damage computer systems - corrupt or change files - steal data - disrupt services
16
Q
Viruses
A
designed to delete or corrupt or steal data
Spreads when someone transfers an infected file from one computer to another
Attaches itself to a legitimate host file and activates when the host program runs
17
Q
good practices
A
dont open emails from unknown sneders
dont visit unkown links
dont plug in untrusted devices
18
Q
Worms
A
replicates and damages system
- doesn’t require a host to spread
Spreads more quickly than viruses
Once it has exploited a vulnerability, it takes advantage of shared storage e.g. email
19
Q
Trojans
A
uses deception to attack a system
looks like a legitimate program
Opens backdoor for further malware and remote control of computer
Computer may become a bot under control of a hacker
Dont replicate like viruses - require human interaction
20
Q
Spyware
A
installed on device without users knowledge
leaks data from computer back to creator of software
Keylogger - keeps record of keys pressed
Easily removed with a spyware removal tool
21
Q
SQL injection
A
user adds additional sql statements within the inputs for these to be executed on the database
Can be avoided by good coding practices
22
Q
Ransomware
A
Locks you out of your computer until you pay a ransome
Encrypts files so they are unusable
Make sure you back up data regularly
23
Q
Denial of service attacks
A
purposely bombarding a server with thousands of ‘legitimate’ requests
Overwhelms the system
24
Q
Database def
A
an organised collection of data
25
Entity def
an object in the real world that can be differentiated from other objects
26
Record
Row - each row stores the data for a specific entity
27
Attributes
Columns
a property of the entity
aka field
Each one has a specific data type
28
Primary key
an attribute or set of attributes that makes an entity uniquely identifiable
- allows the entity to be identified unambiguously
Composite primary key = primary key made up of more than one attribute
29
Foreign key
the primary key of one filed that is stored in another table for the purpose of creating a link between the tables
30
Data integrity
the accuracy and reliability of data
| Achieved via validation and verification
31
Referential integrity
the system will ensure that, when a record is added to a table and a value is entered into a foreign key field, the value exists in the primary key field of the related table
- can be extended
- if a primary key value is changed, matching foreign keys values are automatically updated
- if a record is deleted, any records with matching foreign keys are also deleted
32
Database management system
hides complexity of the physical implementation
33
Normalisation def
technique used to help reduce data duplication when designing data structures
- improves data integrity
34
If adding new data post normalisation
make sure the table remains in normalised form
35
Databases advantages
- reduced duplicated data
- improve data integrity
- eliminates insertion anomalies
- eliminates update anomalies
- eliminates deletion anomalies
36
Database disadvantages
- require more data (for indexing and metadata)
- time consuming to set up
- understanding of normalisation needed (expertise)
- spreadsheets create a quick and easy solution and allows graphs to be produced easily
37
1NF
- each record has a primary key
- data is atomic
- no repeating groups of attributes
38
2NF
- no partial dependencies
39
3NF
- no non-key (transitive) dependencies
| Each attribute is dependent on the key, the whole key and nothing but the key
40
OR mask
Can be used to turn on certain bits of a binary number
| - Whichever bits you want to turn on, apply a mask of 1, all the others mask as 0
41
Libraries
Give you access to many specialist functions e.g. maths operations
Pre written code
+ saves having to rewrite code
+ as long as its from a reliable source, it has usually been thoroughly tested therefore efficient and reliable
42
Advantages of oop
+easier for us to think in terms of objects than to think procedurally
+rewritten classes promote and support code reuse (include advantages about reusable code)
+ child classes can be created to add extra functionality
+ classes are highly modular so are easy to maintain (only needs to be changed in one place)
+encapsulation provides a high level of protection for data (data can never be modified carelessly)
43
Disadvantages of oop
- result in much larger and complex systems being built
- relies on high volumes of message passing which is detrimental to performance
- inheritance can have unintended consequences
- objects can take up large amounts of memory
44
Procedural programming
the program code is divided up into procedures (discrete blocks of code that carry out a single task)
45
Advantages of subroutines
- easier to test and debug
- can be called many times which reduces repeated code
- can manipulate shared data
- can be saved in libraries and imported when needed
46
Object oriented programming
focuses on the objects that make up the system
Object = an entity that encapsulates both data and behaviour
All of the data and procedures/functions of the system belong to one or more objects
Objects collaborate with each other by sending and receiving messages
Objects dont share data
47
Inheritance
one class inherits (takes on) the attributes and methods of another class
48
Deriving boolean expressions from a truth table
consider only the lines that result in an output of 1
49
D type flip flop definition
Synchronous sequential circuit that can be used to store the value of a single binary digit
50
How does a d type flip flop work?
Takes 2 external inputs:
- d (data signal)
- clock signal
Two outputs
- q
-¬q
Has an internal loop which allows the previous output to be stored
When the clock signal is low (0) - changes at d make no difference to the output
When the clock signal is high(1) - the value of d will appear at the output q
¬q is always the inverse of q
51
Edge triggered d type flip flop
This means that the output can only change on the rising edge of the clock
Stops this problem:
if there are changes in the data during the period when the clock signal is high, the output at q will change in line with d. This may not be desirable
52
Annulment
```
A^A = A
AU0 = A
```
53
Idempotent
```
A^A = A
AUA = A
```
54
Complement
```
AU¬A= 1
A^¬A= 0
```
55
Commutative law
X^Y = Y^X
| XVY=YVX
56
Associative law
X^(Y^Z)= (X^Y)^Z
| XV(YVZ)=(XVY)VZ
57
Absorption law
XV(X^Y)=X
| X^(XVY)=X
58
Distributive law
```
X^(YVZ) = (X^Y) V (X^Z)
XV(Y^Z) = (XVY) ^ (XVZ)
```
59
De morgans laws
X^Y = ¬(¬XV¬Y)
XVY= ¬(¬X^¬Y)
- change the operator (and to or/ or to and)
- negate the variables on either side of the operator
- negate the whole statement and simplify
Useful when working with not and brackets
60
The operating system definition
Collection of programs that provide an interface between the user and computer
Acts as a platform on which the other software can run
Handles the operations that are common to different pieces of software running on the same system
Interacts with hardware, provides a user interface and supports security
Manages resources and ensures that the software and hardware can communicate with each other
61
Rules for karnaugh maps
- groups must be horizontal or vertical
- the number of cells in each group must be a power of 2
- groups should be as large as possible
- every 1 in the map must be in at least 1 group
- create the smallest number of groups possible
62
Functions of the operating system explained
Processor scheduling
- determining the order in which processes will be executed, which allows for multitasking
Handling interrupts
- dealing with requests that disrupt the processor's work
Memory management
- recording how memory in the computer is divided and identified so that memory is allocated efficiently between processes that are running
Secondary storage management
-tracking where files and programs are stored and which parts are available for storage, and managing files and folders based on user permissions
Input/Output device management
- ensuring efficient communication with devices and managing functionality issues
63
Other uses of operating system - user interface
hides the complexity of the hardware from users and other software processes
Provides a user interface - the users of the computer interact with the computer and receive the info that it processes
64
Operating system - security
ensures resources are protected from unauthorised access through the use of permissions and passwords
65
Distributed os
Separate computers can be joined together via network connections to work together as a more powerful whole
Coordinates the communication between these computer nodes
+ processor intensive tasks when a single processor cant provide enough computational power on its own
66
Embedded os
Used in computers which only serve a specific purpose e.g. washing machines
+ hardware reliability
+efficient use of resources
- no flexibility in the system
67
Multitasking os
Provides illusion that it is running more than one task at a time by switching between tasks quickly
68
Multi user os
Provides facilities for multiple users to access the same system
Controls consumption of resources so that users can access the same system at the same time
69
Real time os
Supports apps that need to process data to produce an output quickly
- not as flexible as other os
+ ensure consistent response to inputs within a guaranteed time period
Used in systems about saving lives
70
list of functions of an os
- memory management
- resource management
- file management
- i/o management
- interrupt management
- utility software
- security
- user interface
71
memory management
tracking the status of memory allocation
determines storage requirements
controls memory usage
72
paging - form of memory management
- fixed physical size
- allows memory to be allocated non contiguously
- page table uses mapping to store link between the physical memory address and the logical address space
73
segmentation - form of memory management
- varying sizes (logical)
- data doesn't need to be stored contiguously
- segment table - used by os, records where each segment is physically located
- can be moved in an out of memory as required
74
Virtual memory explaination
OS can swap parts of the process that aren't in use from main memory to an allocated space on the hard disk (for example) then swap it back to main memory
75
Virtual memory advantages and disadvantages
+ more memory potentially available
| + accessing secondary storage is slow
76
Device drivers def
provides an interface that allows the os and other software to interact with the device without having to deal with the particular hardware of the device
- specific to computer's architecture
- specific to the os
- installed into the os on demand
77
Basic Input Output System
- first program that runs when a computer system is turned on
- runs a series of tests before the os is loaded into memory
- POST ensures all hardware is correctly connected and functional
Checks the CPU clock, memory and processor
Tests for external memory devices
78
Virtual machines def
a theoretical computer and a software implementation of a computer system
- provides and environment with a translator for intermediate code to run
79
Virtual machines uses
testing program
protection from malware
running software compatible with different types of os
80
LMC instruction set
```
LDA
STA
ADD
SUB
INP
OUT
HLT
BRZ
BRP
BRA
DAT
```
81
System software
controls the hardware of a computer system
It provides a platform for application software to run on and means application software can interact with the hardware it is run on
82
Utility software
-specific type of system software
| Enables to user to configure, control improve and maintain the general operations of the computer
83
Operations covered by utility software
- reorganisation of files on a hard disk
- encryption of data on storage devices
- backing up of data
- diagnostic tools to monitor the operation of key hardware
84
Application software
Designed to perform tasks that a user wants to complete
Some pieces may be preinstalled on a computer, but more often the user has to install the application software on the device
85
Examples of application software
- word processors
- spreadsheet software
- presentation software
- video games
- database management software
- media playback software
- communication software e.g. an email client
86
Class def
blueprint that defines the properties of all objects of the same time
87
1:many relationship
teacher to subject
88
Instantiation
Making an object from the class definition
89
Method
Must define every operation that is allowed to be carried out on an attribute
90
Encapsulation
Binds together the attributes and the methods that manipulate the data
- protects the data
91
Disadvantages of inheritance
Can have unintended consequences
- what happens is someone extends the base class
- what happens if someone changes the base class to inherit from another class
- may have acquired attributes and methods you're not aware of
92
Advantages of inheritance
+ reduces repeated code
| + if implementation detail need to change, it only needs to be changed in one place
93
1:1 relationship
Headteacher to school
94
many:many
teachers to students
