PAPER ONE Flashcards
GET THIS BREAD (98 cards)
1
Q
How are the registers used in the FDE cycle?
A
Fetch - PC holds next instructions address – This is then copied to the MAR – The instruction held in at this address is then copied to the MDR – The PC is simultaneously incremented – The contents of the MDR is then copied to the CIR.
Decode - The instruction held in the CIR is then split into opcode and operand. Opcode determines the type of instruction and the Operand contains either the address, actual data or data to be passed onto the ALU
Decode - The Opcode is carried out on the Operand
2
Q
What are the names and directions of the 3 buses?
A
Control bus - Bi-directional - Used to ensure no conflicts
Data bus - Bi-directional - Used to transfer data between system components
Address bus - One directional - Used to transmit memory addresses of words
3
Q
What is pipelining?
A
A processor technique which allows instructions to be fetched whilst another is being decoded making it seem like processes are simultaneous
4
Q
What are the 3 main factors effecting performance?
A
Clock speed - Amount of processes a second
Number of cores - Instructions at the same time
Amount and type of cache - Memory of frequently used data. Level 1 cache = very fast but small Level 2 = fast but medium size memory Level 3 = Slower but larger amount of memory
5
Q
What is the GPU?
A
Graphics processing unit
Very efficient at manipulating computer graphics and image processing
6
Q
What’s the difference between Von Neumann and Harvard architectures?
A
Von Neumann - Based on the stored program concept (linear processes)
Uses the same data bus to transfer data and instruction
Commonly used in every day computers
Harvard - Uses separate buses for instructions and data as they are held in separate places
Commonly used in embedded systems
7
Q
What’s the difference between RISC and CISC?
A
RISC - Reduced instruction set computers
Only one clock cycle per instruction
Requires more RAM
Pipelining is possible to speed up processing
Hardware is more simple and software more complex
Used in phones
CISC - Complex instruction set computers
Hardware is more complex and software less complex
Used in computers
Uses MULT for multiplication which is a single machine code instruction but will take more cycles.
8
Q
What are multi core and parallel systems?
A
Multi core is when there is more than one CPU which can parallel distribute workload across these cores.
The improvement in performance however depends on the software
9
Q
What are the two types of barcodes?
A
Linear - like shopping ones
2D quick response QR used on tickets
10
Q
What are some barcode readers?
A
Pen type reader - a light source and onto diode are at the end of pen to read barcode
Laser scanner - use laser beam as light source and a photo diode
Camera based readers - imaging scanner using camera and processing techniques
11
Q
What is RFID and the difference between passive and active tags?
A
Radio frequency identification -
Used in bank cards and animal trackers
Active tags are larger and include a battery so it actively transmitted a signal
Passive tags are cheaper and do not have a battery. It has to be energised to send the data to the reader nearby. Used in contactless cards
12
Q
What’s the difference between LCD and OLED screens?
A
LCD are glass and contain red blue and green diodes to form each pixel
OLED are thinner, plastic and therefore can be shaped, brighter and lighter
13
Q
What is an actuator?
A
Motors that are commonly used in conjunction with sensors to control a mechanism.
Eg opening a window in a house
14
Q
What type of storage is a hard disk and what’s their pros and cons?
A
Magnetic storage
+ huge capacity
+ cheaper
+ good for desktops
- Uses moving parts (arm to read disk)
- less portable
15
Q
What type of storage is SSD and what are the pros and cons?
A
Flash storage
Consists of millions of NAND gates
+ consume less power
+ less susceptible to damage
+ lighter and highly portable
+ Silent in operation
- expensive
- less storage
- shorter lifespan
16
Q
What’s the difference between RAM and ROM?
A
RAM is volatile storage
ROM is non volatile storage which stores the OS
17
Q
What is virtual storage?
A
This is storage used when the RAM becomes full and uses the hard disk to free up some space in RAM temporarily
18
Q
What are the 5 functions of an operating system?
A
Memory management
Interrupt service routines
Processor scheduling
Backing store management
Manages inputs and outputs
19
Q
What’s paging and segmentation?
A
They’re both used for memory management
Paging - dividing memory into fixed 4Kb pages and a process can be held in disconnected pages
Segmentation - the logical division of address space depending on program structure
20
Q
What is an interrupt?
A
An interrupt is a signal from a software program, hardware device or internal clock to the CPU to carry out a process
21
Q
What are the objectives of the schedular?
A
Maximise throughput (fast)
To be fair to all users on a multi user system
Provide acceptance response time to all users
Ensure hardware are kept as busy as possible
22
Q
What are the 5 types of scheduling?
A
Round robin - processes are dispatched on a FIFO basis with each process having a time slice. If the process is not finished in this time it will move on
First come first served
Shortest time remaining- requires to know how long jobs will take
Shortest job first - different as it is the running time
Multi-level feedback queues- designed to give preference to short jobs, I/O bound processes and prioritised processes
23
Q
What is a distributed operating system?
A
A form of parallel processing which spreads the load over multiple computer servers
24
Q
What is a multi tasking system?
A
Most PC’s as they can run multiple applications simultaneously
25
What features does a real time operating system have?
Must respond very quickly to may inputs or sensors
Deal with many inputs simultaneously
Must have a ‘failsafe’ mechanism if hardware fails
It must incorporate redundancy meaning if one components fails it should automatically switch
26
What is utility programs and what are some examples?
Utility programs are designed to optimise the performance of the computer.
Disk defragmentation - a program which re organises a magnetic hard disk so that files that are split up are stored closer together in blocks so that the files can be read quicker
Automatic backup and updating
Virus checker - checks hard drive and possibly emails and removes them
Compression software - zip or compress files that can be transmitted much faster
27
Whats the difference between 'off the shelf' and bespoke software?
'Off the shelf' is less expensive since the cost is shared, it may contain not needed features, however it is ready to be installed immediately and is well documented,tested and error free.
Bespoke software is tailored to a specific purpose of a business and is more costly therefore. The features are customised to user requirements. However it may take a long time to develop and may contain errors which do not surface immediately.
28
What's the difference between closed and open source software?
Closed source software is sold in the form of a license and the users will not have access to the source code
Open source software is available to anyone and the source code is available meaning anyone can modify it too.
29
What is an assembler?
A program which translates assembly source code into machine code
30
What is a compliler and it's advantages over interpreters?
A program which translates high level language source code into machine code (object code which can be run when needed)
+ Object code executes faster than interpreted code
+ Can be executed without the compiler present
+ More secure since it cannot be read without extensive measures
+ Can be saved and ran whenever without need to recompile unless there's errors
(Useful for programs run regularly or frequently)
31
What is an interpreter and the advantages over a compiler?
The interpreter is a program which looks at each line of the source code and check for syntax errors. If there isn't any then it translates it into machine code and runs it (python)
+ Platform independent (can run on any machine)
+ Useful for program development
- May run slower than a compiled program
32
What are the 3 stages of compilation and what does each stage do?
Lexical analysis - Removes spaces and comments, performs some simple error checking and keywords are replaced with'tokens'. The symbol table contains an entry for every keyword in the program. (like a variable table)
Syntax analysis - the process of determining whether the sequence of input characters form a valid sentence in the language. There is also parsing used which is applying rules to determine is validity and also semantics are checked which checks the meaning of the language such as declared variables.
Code generation and optimisation - translates high level code into machine code and then attempts to reduce the execution time. This can sometimes make compilation time longer and may get unexpected results.
33
What are linkers and loaders?
Once a program is compiled, any subroutines must be linked to the object code and then the loader can load the object code anywhere into memory.
34
What are already existing libraries and the benefits?
They are ready compiled programs which can be loaded and run when required.
These are good as they are tested and error free and save the programmer time.
35
What are blackbox, whitebox, alpha and beta testing?
Black box - carried out independently of the code and checks the the specification covers all inputs, outputs and functions
White box - carried out dependent on the code as it checks the structure and possible paths but wont test missing functions
Alpha - carried out by software developers testing team
Beta - carried out by potential users as it is released to the public to look for bugs
36
What are the 5 models for product development and explain them!
Waterfall lifecycle model - each step is completed one at a time completed fully from the beginning to the end.
Spiral model - Uses iterative stages where you go through the cycle multiple times, revising and editing a prototype until finished.
Agile model - May not be completed in a linear sequence and they may choose to edit previous parts depending on feedback from prototype performance from users. It is still incremental though with user participation to provide what the users want.
Extreme programming - Adopts short and rapid improvements to fit the changing customer requirements (usually with software)
Rapid application development (RAD) - Adopts a fast completion of major projects as it understands that users needs change. Produces a good enough system which may not be perfect. Uses focus groups to gather requirements fast.
37
What is an algorithm?
A set of steps taken to solve a goal or problem
38
What are the 4 programming paradigms?
Procedural - Series of instructions
Object-oriented (OOP) - Abstracts details of implementation away from the programmer which makes the code reusable and easy to maintain.
Declarative - Write statements that describe the problem to be solved and the language decides the best way (SQL)
Functional - Functions are fundamental building blocks of a program
39
What is object oriented programming and what does it involve? (inheritance, polymorphism, encapsulation and constructors)
We can define a class (e.g animal) and an object can be created as an instance of the class (e.g dog).
Inheritance is when a subclass have the same attributes as the superclass but with possibly added extras.
Polymorphism is when a subclass redfines a method from the superclass to process objects in the class differently
Encapsulation is when attributes cannot be accessed through the class methods if they are declared as private
Constructors are used to create a new object
40
What are the benefits of OOP?
Forces extensive planning which results in better products
The code can be independently edited without effecting the rest of program
New objects can be easily created with small differences to existing ones
Objects can be reused
Easier to maintain
41
What are the mnemonics in assmebly code for storing, loading, branching if zero, if zero unconditional and halting the program
```
Storing = STA
Loading = LDA
Branch (unconditional) = BRA
Branch if zero = BRZ
Branch if positive = BRP
Halting = HLT
```
42
What are addressing modes and the 4 types of them?
It is a part of Opcode which consists of binary digits representing the basic operation such as ADD.
There are four different types:
Immediate addressing - the Operand is the actual value to be operated on
Direct addressing - the operand holds the memory address of the value to be operated on
Indirect addressing - the operand is the location which a register is that holds the address
Indexed addressing - the address of the operand is obtained by adding to the contents of a general register to a constant value
43
What is the difference between lossy and lossless compression?
Lossy = Compression where non-essential information is permanently. Used for images which do not make a difference to the human eye and MP3 files which pitched sounds which the human ear cannot hear are removed.
Lossless = Compression by finding patterns in data and compresses data which can be reversed to obtain the original information. Used for word files or pictures which need a high quality.
44
How does Run-length encoding (RLE) work?
Records the amount of times the data is repeated and then the value
Example - A pictures pixel colours may be 6Green 8Yellow 9Red which uses less data needed to be stored
45
How does dictionary based compression work?
A number is paired with a word or value and every time that word is repeated it uses the same value paired to it The dictionary must also be sent with the data to be able to decode it
46
Define encryption!
Encryption is the transformation of plain text to cipher text in order to prevent a third party from being able to understand it.
The encryption algorithm is known as the cipher and the secret information to lock or unlock the message is known as the key.
47
What is the difference between symmetric and asymmetric encryption?
Symmetric encryption (private key encryption) uses the same key to encrypt and decrypt the plain text/ciphertext. This has obvious security problems where the key can be intercepted to decrypt the ciphertext
Asymmetric (public key) encryption uses two keys. The public key is made public so that others wishing to send you data can use this to encrypt it. this key cannot decrypt. The private key which is known by only you can be used to decrypt data. Messages can be digitally 'signed' to authenticate senders.
48
What is hashing?
Hashing applies a hash function which cannot be reversed. This is used with passwords and the hashed password is checked against the hashed password entered.
49
How does digital signatures work in terms of hashing?
The sender uses their private key to encrypt the hash total which is the digital signature. The receiver decrypts the message with their private key and the signature with the senders public key.
50
Whats the difference between a flat file and relational database?
A flatfile database is a signle table/file which is almost like a list
A relational database is a collection of tables in which relationships are modeled by shared attributes
51
What is a primary, secondary, foreign and composite key?
Primary key = a unique identifier for a table /object
Secondary key = a secondary index which is recognisable by humans. Example is that people wont know their ID but their name may be the second key
Foreign key = a primary key existing in another table which links two tables
Composite key = a combination of keys such as house number and street which can return one output instead of both.
52
What is referential integrity?
Referential integrity is checking that everything is valid and existing, such as depositing money into a bank account, the users bank account must be valid and created first.
53
Define normalisation!
Normalisation is the process of coming up with the best possible design for a relational database.
54
What is first, second and third normal form?
A table is in first normal form if there are no repeating attributes or groups of attributes
A table is in second normal form if it is in first normal form and contains no partial key dependencies meaning their are attributes which depend on only part of the primary key (e.g a composite key)
A table is in third normal form if it is in both first and second normal form but also there are no non-key dependencies ( attributes must be dependent on the key, the whole key and nothing but the key)
55
What are the benefits of normalisation?
No data redundancy (appears multiple times)
Data integrity (data is only stored once)
Easy to maintain and modify
Fast sorting and searching
56
How do you write a SQL query?
SELECT ____ ( * if all and use a song.artist if the attribute appears in multiple tables)
FROM (table)
WHERE (conditions)
ORDER BY
57
How do you create a table in SQL?
```
CREATE TABLE _____
(
EmpID INTEGER, PRIMARY KEY,
EmpName VARCHAR(20),
HireDate DATE,
Salary CURRENCY
)
```
MUST USE COMMAS WHEN LISTING
58
How do you alter, insert, update and delete data in SQL?
Alter =
ALTER TABLE ____
ADD/DROP/MODIFY ____ (datatype)
Insert =
INSERT INTO tablename (column1, column2)
VALUES (value1, value2)
Update =
UPDATE tablename
SET column 1 = value1, value2, value3
WHERE columnx = value
Delete =
DELETE FROM tablename
WHERE columnx = value
59
During transaction processing what is ACID?
Atomicity = the transaction is processed entirely or not at all.
Consistency = ensures that no validation rules are broken such as referential integrity
Isolation = ensures that concurrent transactions leads to the same result as if they were processed linearly
Durability = ensures that once it is committed it will remain so even in the event of a power cut or natural disaster.
60
What are some methods that may be employed to avoid updates in a multi user database to be lost?
Record locks - Preventing simulatneous access to objects in a database. A record is locked when a user attempts to edit or update. However this can cause a deadlock where two users are waiting for the other to finish.
Serialisation - Either timestamp ordering which when a transaction starts, it is given a timestamp and the earlier one has priority. OR commitment ordering which ensures the updates are not lost as they are ordered by dependency as well as time.
Redundancy - Maintaining identical systems in different geographical locations in case one goes down.
61
What is a domain name?
A domain name identifies the area or domain that an internet resource lies
62
What is an IP address?
Internet protocol
It is a unique address assigned to a network device.
63
What is the difference between LANS and WANS
Local area network - small geographical location such as a single building where there are interconnected networks
Wide area network - a large geographical location such as a city
64
What are the advantages and disadvantages of a BUS TOPOLOGY vs a STAR TOPOLOGY vs a MESH NETWORK?
```
BUS -
+ Requires less cable and is therefore cheaper
- If main cable fails then all does
- Performance worsens as heavy traffic
- Low security
STAR -
+ If cable fails only one breaks
+ No difference in performance when high traffic
+ No problem with collisions
+ More secure
+ Easy to add new stations
- Costly
- If central server goes down its peak
MESH NETWORK -
+No cabelling costs
+ More nodes installed make the network faster and more reliable (self-healing)
+Faster communication
```
65
What is the difference between circuit and packet switching?
Circuit switching creates a direct link between two devices for the duration of the communication (PUBLIC PHONES
Packet switching is a method of communicating packets of data across a network on which other similar
communications are happening simultaneously.
A packet is data which is broken down to be transmitted across a network
66
What is a MAC address?`
A hard coded 12 hex digit address which is assigned to a device as a unique identifier
67
Describe and explain the four layers in the TCP/IP stack!
Various protocols operate at each layer of the stack with different roles.
Application layer - At the top of the stack and uses protocols relating to the application being used to transmit data over a network.
Transport layer - Uses TCP to establish an end to end connection with the recipient computer. The data is then split into packets and labelled with the packet number and the port.
Network layer - Adds the source and destination's IP addresses.
Link layer - Physical connection between network nodes and adds the MAC addresses of the source and destination computers.
68
What is FTP?
File transfer protocol which is used in the Application layer by dragging the files from one area to another
69
What is a mail server?
Acts as a virtual post office for all incoming and outgoing emails.
70
What is a firewall?
A security checkpoint designed to prevent unauthorised access between two networks (usually one trusted and one untrusted)
71
What does a proxy server do?
It intercepts all packets entering and exiting a network, hiding the true network address of the source from the recipient.
72
What are viruses and worms?
They have the ability to self-replicate by spreading copes of themselves.
A worm is a subclass of a virus but viruses rely on host files (executable files) to be opened in order to spread whereas worms do not
73
What is a trojan?
It manifests itself inside of a seemingly useful file, game or utility that you may install and it can access personal information.
74
What's the difference between identifiers and classes in HTML?
Identifiers you use a # used for unique values
Classes use a . but used for when multiple values are apparent.
75
How does search engine indexing work?
Search engines rely on a database or index of web pages to find the pages you are looking for. This can be used with web crawlers / spiders that look for keywords, meta tags and descriptions to match your search.
76
How does Google's pagerank system work?
Previously pages were ranked by the amount of times it had been visited.
However, Google developed a pagerank system which considers the amount of views, importance and reputation
77
What is client server networking and the pros and cons of it?
One or more computers kown as clients which are connected to powerful central computer known as a server
+ Security is better
+ Backups are done centrally
+ Data and other resources can be shared
- Expensive to install and manage
- Professional staff are needed such as IT tehnician
78
What is peer to peer networking and the pros and cons of it?
There is no central server and computers are connected to each other either locally or over a wide area network so they can share files.
+ Cheap to set up
+ Enables users to share resources such as a printer
+ Not difficult to maintain
- Impossible to trace the files which are being illegally downloaded
79
What is the difference between client and server side processing?
Processing on the clients computer to lighten the load on the server such as javascript
Processing on the server often process an enormous volume of data on behalf of the client as it is faster.
80
Define API (application programming interface)!
A set of protocols that govern how two applications should interact with one another.
81
What is the advantages of thick vs thin client computing?
Thick = a larger amount of processing and storage that it does compared with the server
+ Robust and reliable
+ Doesn't need a continuous connection to the server
+ Better for running more powerful software applications
- More expensive and higher spec needed on computer
- Installation of software required needed on each terminal
Thin = a larger amount of processing and storage that the server does compared to the client
+ Easy to set up, maintain and add terminals
+ Software and updates can be installed on the server
+ More secure as data is kept centrally
- Reliant on server and if it fails then loses functionality
- Requires a very powerful and reliable server which is expensive
- Server demand and bandwidth increased
82
What is the difference between kibi and kilo in terms of bytes?
```
Kibi = 1024
Kilo = 1000
```
83
What's the difference between ASCII and Unicode?
ASCII uses an 8-bit code which have 128 characters
Unicode uses a 16-bit code which have 256 characters
and then a further version with 32-bit code which have over a million characters
84
What is a tuple?
an ordered set of values of elements which do not have to be the same data type. Elements can't be changed or added to.
85
What is an ADT?
Abstract data type
It is a data type created by the programmer rather than defined within the programming
86
What is a queue structure and what operations are there?
FIRST IN FIRST OUT (FIFO)
New elements may only be added to the end.
```
enQueue() = add
deQueue() = remove
isEmpty() = Test to see whether the queue is empty
isFull() = test to see if it is full
```
87
Whats the difference between dynamic and static structures?
Dynamic can grow or shrink in size whereas static cannot
88
What's the difference between a linear queue and a circular queue?
Linear = As items leave the queue all items move up one position or use of front/rear pointers.
Circular = pointers which can point rear at the beginning of a list
89
Define a list and what is the difference between a list and an array?
An abstract data type consisting of a number of items which may occur multiple times
A list is dynamic in structure whereas an array has to be declared of its size before hand.
90
What is a linked list and how is it structured?
A dynamic data structure which always has a pointer the first item in the list and one which points to the next free node. There is a node containing the element and then the value.
91
What is a stack and the operations on the stack?
```
LAST IN FIRST OUT structure which has the operations of:
push(item)
pop()
peek()
isEmpty(0
isFull()
```
92
What are the two ways of traversing a graph and a tree?
Breadth first and depth first for tree
Tree = pre-order, inorder and post order traversal
93
What is the difference between a tree and graph?
A tree may be rooted and can only have two nodes branching from a node.
94
What is De Morgans law?
¬(A v B) = ¬A ^ ¬B
95
What is the Data Protection Act 1998?
States that data must be fair, lawful, relevant, accurate, secure, not transferred to anyone outside and not retained for longer than necessary.
96
What is the Computer Misuse Act 1990?
Recognises the offences of unaurthorised access to computer material, with intent to commit a crime and modifying computer material.
97
What is the Copyright Designs and Patents Act 1988?
It is illegal to pass a copy to a friend, make a copy then sell it and use software on a network unless license allows it.
To prevent this the user may enter a unique key before download, some need a CD present and some may only run on a USB.
98
What is the Regulation of Investigatory Powers Act 2000?
Enables certain public bodies to demand somones ISP, enables mass surveillance of communications in transits, enables certain public bodies to monitor peoples internet activities
