A451 - Ocr Computer Science

Front 1

What is a computer system?

Back 1

Any system of which data can be inputted, processed and outputted.

Front 2

What is a special-purpose machine?

Back 2

Special Purpose Machines are computing systems that are designed to do one thing.

Front 3

What are binary number?

Back 3

Binary numbers are numbers that are in the base 2 number system consisting of 1's and 0's, these are the numbers that computers understand.

Front 4

What is overflow?

Back 4

Overflow is when the answer of an addition or subtraction problem exceeds the magnitude which can be represented with the allotted number of bits.

Front 5

Why 1's and 0's?

Back 5

The 1 and 0 digits in binary correspond to the on and off states of a transistor.

Front 6

What are denary numbers?

Back 6

Denary/Decimal numbers are numbers that are part of the base 10 number system, that we use in everyday life.

Front 7

What is bit depth?

Back 7

The number of bits available to store something.
e.g. Images and audio files have bit depth.

Front 8

Examples of bit depth. (Just turn over).

Back 8

A 1-bit system uses combinations of numbers up to one place value. There are just two options: 0 or 1. There fore the bit depth is 2.

A 2-bit system uses combinations of numbers up to two place values. There are four options: 00, 01, 10 and 11.

Front 9

What is the CPU?

Back 9

CPU - is the 'brain' of the computer and executes instructions using the fetch-decode-execute cycle.

Front 10

What is Memory?

Back 10

* Memory - stores program operations and data while a program is being executed. There are several types of memory, including: registers, cache, RAM and virtual memory.

Front 11

What is storage?

Back 11

* Storage - stores programs and files long term, even when they are not in use. Devices such a shard drives, USB memory sticks or SD cards are used to store files such as photos, music and software applications long term.

Front 12

What is the GPU?

Back 12

The GPU is responsible for handling images and frees the CPU to do other tasks.

Front 13

What affects CPU performance?

Back 13

CPU (clock) speed, the amount of cores, the processor type, memory/cache memory size and bus speeds all affect the CPU'S performance

Front 14

What is inside a core?

Back 14

An ALU (Arithmetic Logic Unit).

A Control Unit.

And registers.

Front 15

How do cores communicate?

Back 15

Cores communicate through channels.

Front 16

Examples of cores and channels communicating.

Front 17

What is the type of speed that measures how fast the CPU can run and what is it's unit?

Back 17

Clock speed/Clock rate and it is measured Hz.

Front 18

What is cache and what does it do?

Back 18

Cache is a small amount of memory which is a part of the CPU. It is used to temporarily hold instructions and data that the CPU is likely to reuse, saving the CPU from fetching the same data and instructions from RAM repeatedly.

Front 19

What is Level 1 (L1) cache?

Back 19

* L1 is usually part of the CPU chip itself and is both the smallest and the fastest to access. Its size is often restricted to between 8 KB and 64 KB.

Front 20

Explain L2 and L3 cache.

Back 20

* L2 and L3 caches are bigger than L1. They are extra caches built between the CPU and the RAM. Sometimes L2 is built into the CPU with L1. L2 and L3 caches take slightly longer to access than L1. The more L2 and L3 memory available, the faster a computer can run.

Front 21

Name the two processor types?

Back 21

CISC - Complex Instruction Set Computing architecture made by Intel and AMD.

RISC - Reduced Instruction Set Computing, used by smartphones and from ARM architecture.

Front 22

Compare the differences in instructions, speed, size, cost, energy consumption and design of RISC and CISC.

Back 22

The key differences between the two CPUs are:

* Instructions - RISC has fewer instructions than CISC. CISC generally have hundreds of instructions whereas RISC usually has a lot less. To do complex tasks, RISC CPUs must combine simple operations from their reduced instruction set. The instruction cycle in CISC is more complex than RISC, so RISC can be more efficient at performing simpler tasks.
* Physical size - in order to handle all those instructions CISC CPUs are larger and require more silicon to make.
* Speed - RISC CPUs run at a lower clock speed than CISC CPUs. They can perform simpler tasks more quickly than CISC, but more intensive tasks will be better on a CISC CPU. However, smartphones and tablets are generally not used to do intensive tasks like playing the most hi-spec advanced games.
* Energy consumption - because CISC CPUs are larger, they use more electricity. RISC CPUs are designed to use less power and they can go into 'sleep mode' when not actively processing a program.
* Design - smartphones and tablets combine their processing architecture into a system on a chip (SOC). As RISC CPUs are much smaller than CISC, more functions (including the memoryand other hardware) can be combined with the CPU in one chip. CISC CPUs are usually built into a system which has a heat sink and fan to cool them down. Smartphones or tablets do not have space for heat sinks or fans.
* Cost - RISC CPUs use less power and are cheaper to make.

Front 23

What is ASCII?

Back 23

ASCII (American Standard Code for Information Interchange) is the most common, standard format for text files in computers and on the Internet.

Front 24

How are characters represented in ASCII files?

Back 24

In an ASCII file, each alphabetic, numeric, or special character is represented with a 7-bit binary number (a string of seven 0s or 1s). 128 possible characters are defined.
However the computer interprets the character in 8 bits for ease.

Front 25

What are the limitations of ASCII?

Back 25

Only letters and numbers in the English language are defined leading to miscommunication in regards to foreign languages.

Front 26

How can this be solved?

Back 26

By using a two byte (16-bit) character set such as unicode which allows for 65, 000+ characters.

Front 27

How does unicode handle different languages?

Back 27

By dividing the total 'unicode space' into code pages which are sections for different languages.

Front 28

What is a character set?

Back 28

A defined list of characters recognized by the computer hardware and software. Each character is represented by a binary number.

Front 29

What are hexadecimal numbers?

Back 29

Hexadecimal numbers are numbers that are part of the base-16 number system and it is by humans to simplify how binary numbers are represented.

Front 30

What numbers are part of the hexadecimal number system?

Back 30

0 1 2 3 4 5 6 7 8 9 A B C D E F

Front 31

When is hexadecimal used?

Back 31

* colour references
* assembly language programs
* error messages

Front 32

How do you convert from decimal to hex.

Back 32

Convert from binary to decimal, then decimal to hexadecimal.

Front 33

How do we convert from binary to hex?

Back 33

Split the binary number into two nibbles, find the corresponding hex value for each nibble and 'paste' them together.

Front 34

How do we convert from hexadecimal to decimal?

Back 34

The first the number is in the 1's column and the second is in the 16. Times the corresponding numbers by their column headers and add them together.
e.g.

|16|1|

-----------

|3 | A |

3 x 16 = 48

A = 10, 10 x 1 = 1
48 + 10 = 58

Front 35

What are networks?

Back 35

A network is created when more than one device is connected together. Computers in a network can share data that are in the shared domain in the form of data packets.

Front 36

What are data packets?

Back 36

Data packets are files that have broken up into chunks of data to be transmitted over a network. The data is then rebuilt once it has reached the destination computer.

Front 37

What are network protocols?

Back 37

Protocols are a set of guidelines that govern how data is broken up into data packets and transmitted over a network.

Front 38

Name some advantages of networks.
(Four Points)

Back 38

Advantages

* Communication – it is easy (and often free) to communicate using email, text messages, voice calls and video calls.
* Roaming – if information is stored on a network, it means users are not fixed to one place. They can use computers anywhere in the world to access their information.
* Sharing information – it is easy to share files and information over a network. Music and video files, for instance, can be stored on one device and shared across many computers, so every computer does not need to fill the hard drive with files.
* Sharing resources – it is easy to share resources such as printers. Twenty computers in a room could share one printer over a network.
* Sharing software – it is possible to stream software using web applications. This avoids needing to download and store the whole software file.
*

Front 39

Name some disadvantages of networks?

(Four Points)

Back 39

Disadvantages

* Dependence – users relying on a network might be stuck without access to it.
* Hacking - criminal hackers attempt to break into networks in order to steal personal information and banking details. This wouldn't be possible on a stand-alone computer without physically getting into the room, but with a network it is easier to gain access.
* Hardware – routers, network cards and other network hardware is required to set up a network. At home, it is quite easy to set up a wireless network without much technical expertise. However, a complicated network in a school or an office would require professional expertise.
* Viruses - networks make it easier to share viruses and other malware. They can quickly spread and damage files on many computers via a network.

Front 40

Name three different types of networks.

Back 40

LAN, WAN, VPN, WPAN and PAN are all types of networks.

Front 41

What is LAN?

Back 41

A LAN (local area network) is a network of computers within the same building, such as a school, home or business. A LAN is not necessarily connected to the internet.

Front 42

What is a WAN?

Back 42

A WAN (wide area network) is created when LANs are connected. This requires media such as broadband cables, and can connect up organisations based in different geographical places. The internet is a WAN.

Front 43

What is a VPN?

Back 43

A VPN (virtual private network) is usually hosted securely on another network, such as the internet, to provide connectivity. VPNs are often used when working on secure information held by a company or school.

Front 44

What is WPAN?

Back 44

A WPAN (wireless personal area network) allows an individual to connect devices (such as a smartphone) to a desktop machine, or to form a Bluetooth connection with devices in a car. A wired personal network is called a PAN (personal area network).

Front 45

What are the three different network topologies?

Back 45

Bus, Ring and Star.

Front 46

Describe the design of a bus network.

Back 46

In a bus network all the workstations, servers and printers are joined to one cable - 'the bus'. At each end of the cable a terminator is fitted to stop signals reflecting back down the bus.

Front 47

State the advantages to the bus topology.

Back 47

Advantages

* easy to install
* cheap to install - it does not require much cabling

Front 48

State the disadvantages to the bus topology.

Back 48

Disadvantages

* if the main cable fails or gets damaged, the whole network will fail
* as more workstations are connected, the performance of the network will become slower because of data collisions
* every workstation on the network 'sees' all of the data on the network, which can be a security risk

Front 49

Describe the design of a ring network.

Back 49

In a ring network, each device (eg workstation, server, printer) is connected in a ring so each one is connected to two other devices. Each data packet on the network travels in one direction. Each device receives each packet in turn until the destination device receives it.A

Front 50

State an advantage to the ring topology.

Back 50

Advantages

* this type of network can transfer data quickly (even if there are a large number of devices connected) as data only flows in one direction so there won't be any data collisions

Front 51

State a disadvantage to the ring topology.

Back 51

Disadvantages

* if the main cable fails or any device is faulty, then the whole network will fail - a serious problem in a company where communication is vital

Front 52

Describe the design of a star network.

Back 52

In a star network, each device on the network has its own cable that connects to a switch or hub. This is the most popular way of setting up a LAN. You may find a star network in a small network of five or six computers where speed is a priority.

Front 53

State two advantages of the star topology.

Back 53

Advantages

* very reliable – if one cable or device fails, then all the others will continue to work
* high performing as no data collisions can occur

Front 54

State three disadvantages of the star topology.

Back 54

Disadvantages

* expensive to install as this type of network uses the most cable, and network cable is expensive
* extra hardware is required - hubs or switches - which add to the cost
* if a hub or switch fails, all the devices connected to it will have no network connection

Front 55

Connections between computers on a network can be... (please complete).

Back 55

Wired or wireless.

Front 56

What is needed for wired connections.

Back 56

Ethernet cables which connect to the Ethernet port of devices. E.g. Computers connect to wireless routers with a ethernet cable.

Front 57

What is needed for wireless connections?

Back 57

A computer with a network interface card and a wireless router.

Front 58

State the advantages of wireless networks.

Back 58

Advantages

* cheap set-up costs
* not tied down to a specific location
* can connect multiple devices without the need for extra hardware
* less disruption to the building due to no wires being installed

Front 59

State the disadvantages of wireless networks.

Back 59

Disadvantages

* interference can occur
* the connection is not as stable as wired networks and can 'drop off'
* it will lose quality through walls or obstructions
* more open to hacking
* slower than wired networks

Front 60

What is a router?

Back 60

A device which forwards data packets to their destinations via the most efficient route.

Front 61

What is a repeater and why do we use it?

Back 61

Signals fade as they travel from one place to another and each type of cable used for networking has a maximum useable length. Repeaters are set in places that ensure that the cables never meet/exceed their maximum length and boost their network signal back up to its' correct level.

Front 62

What is a bridge?

Back 62

A bridge joins one network to another so as far as data packets are concerned it is just one large network.