Topic 3 Hardware CIE IGCSE Computer Science

Describe the purpose of the control unit within this computer

It sends control signals; [1 mark]

● … that manage the transfer of data and instructions within the CPU; [1 mark]

● It decodes an instruction; [1 mark]

● … using an instruction set; [1 mark]

State purpose of a core in a CPU

process an instruction
to carry out an FDE cycle

Literally most sensor questions

Infrared sensor

Send signal to microprocessor

Signal is analogue and converted to digital using ADC

data compared to stored value

If does not match

Increment counter by 1

Continue process

Devices that can be used for input

Keyboard

Mouse

Microphone

Keypad

Touchscreen

Touchpad

Ron is attending a music concert. He has bought three tickets.

Each ticket number is displayed as a hexadecimal number.

Each ticket also has a QR code. TheQR code is scanned at the entrance to the venue.

A person can only enter the venue with a validQR code that allows entry.

When a person enters, a count is incremented to show how many people have entered the venue.

Explain how the system scans the QR code, checks if a person can enter and counts how many people have entered

Camera captures code // Laser/light shone on code; [1 mark]

− Black squares reflect different light to white; [1 mark]

− Corner squares are used for alignment; [1 mark]

− Pattern converted to digital data // by example; [1 mark]

− (Digital) data sent to microprocessor; [1 mark]

− There is a database of valid QR codes; [1 mark]

− Data compared to stored values/valid QR codes …; [1 mark]

− … If data matches entry is granted is raised; [1 mark]

− … If data matches count is incremented; [1 mark]

− … If data does not match, entry is denied; [1 mark]

What is LED?

− Light emitting diodes (technology); [1 mark]

− The display is made up of pixels; [1 mark]

− … that are arranged together as a matrix; [1 mark]

− … each is formed of three LEDs/filters; [1 mark]

− Shades of colour are achieved by mixing red, blue and green; [1 mark]

− The screen can be back-lit/edge-lit; [1 mark]

Benefits of LED

− Energy efficient // low power consumption; [1 mark]

− Long lasting // longevity; [1 mark]

− Focussed beam // less light strays from beam ; [1 mark]

− Brighter/vivid colours ; [1 mark]

− High resolution; [1 mark]

− No flicker; [1 mark]

− Display is thinner; [1 mark]

− Mercury free technology // environmentally friendly; [1 mark]

− Fewer pixel failure; [1 mark]

− Increased viewing in sunlight; [1 mark]

LED table

What is LCD?

− Liquid crystal display; [1 mark]

− The display is made of pixels; [1 mark]

− … arranged in a matrix; [1 mark]

− Uses a flat panel display; [1 mark]

− Backlit display; [1 mark]

− … with CCFLs/LEDs; [1 mark]

− Uses light-modulating properties of liquid crystals; [1 mark]

− Crystals can be turned between opaque and transparent (to allow light to pass); [1 mark]

− Colours created using RGB; [1 mark]

Benefits of LCD

Low power consumption; [1 mark]

− Runs at cool temperature; [1 mark]

− Do not suffer image burn; [1 mark]

− Do not suffer flicker issues; [1 mark]

− Bright image/colours; [1 mark]

− High resolution image; [1 mark]

− Cheaper to purchase than e.g. LED screen; [1 mark]

CD & DVD similarities

Both need a red laser to read/write data; [1 mark]

− Both are spun to be read; [1 mark]

− Both use spiral tracks for data; [1 mark]

− Both are optical storage; [1 mark]

− Both are off-line storage // both non-volatile; [1 mark]

− Both use pits and lands to store data; [1 mark]

CD & DVD differences

− DVD can be dual layer, but CD can only be single; [1 mark]

− DVD has higher storage capacity; [1 mark]

− DVD has a shorter wavelength laser; [1 mark]

− DVD are spun faster; [1 mark]

− DVDs have a higher data transfer rate; [1 mark]

Explain to Kamil why it is better to use DVD-RAM rather than DVD+RW or DVD-RW

– direct access because of concentric tracks; [1 mark]

– can read and write at the same time because it has a read/write head; [1 mark]

Draw a diagram to represent how virtual memory is created and used

Explain why virtual memory is needed

to extend the RAM capacity; [1 mark]

● … to stop the 3D modelling software from freezing/crashing when the physical RAM is full; [1 mark]

● to allow the computer to process the large amount of data required for 3D modelling; [1 mark]

What is SSD, how does it work?

− Solid state drive; [1 mark]

− Non-volatile; [1 mark]

− Secondary storage; [1 mark]

− Flash memory; [1 mark]

− Has no mechanical/moving parts; [1 mark]

− Uses transistors; [1 mark]

− … and cells that are laid out in a grid; [1 mark]

− Uses control gates and floating gates; [1 mark]

− Can be NAND/NOR (technology); [1 mark]

− Use EEPROM technology; [1 mark]

Operating

− Stores data by flashing it onto the chips; [1 mark]

− Data stored by controlling the flow of electrons through/using transistors/chips/gates; [1 mark]

− The electric current reaches the control gate and flows through to the floating gate to be stored; [1 mark]

− When data is stored the transistor is converted from 1 to 0; [1 mark]

Differences between flash memory and CD-RW

Flash memory

– solid state memory

– no formatting issues

– plugs directly into the USB port

– direct transfer of data

CD-RW

– optical media

– slower access speed/flash memory has faster access speed

– requires a separate drive

– data needs to be burnt/finalised/finished (before being used on another device)

What is meant by a MAC address

used to identify a device; [1 mark]

● it is a unique (address); [1 mark]

● it is a static address // it does not change; [1 mark]

● it is set by the manufacturer; [1 mark]

● the first part is the manufacturer ID / number / identifies the manufacturer; [1 mark]

● the second part is the serial number / ID; [1 mark]

Characteristics of an IP address

consists of values between 0–255 / 0–FFF; [1 mark]

● values are separated by full stops / colons; [1 mark]

● it is a unique address; [1 mark]

● can be static or dynamic; [1 mark]

● can be public or private; [1 mark]

● can be IPv4 / have four groups of digits; [1 mark]

● can be IPv6 / have eight groups of digits; [1 mark]

● in IPv6 :: can replace groups of zeros; [1 mark]

IP address and MAC address similarities

Both addresses can be used to identify a computer/device; [1 mark]

− Both are unique; [1 mark]

− Both can be represented as hexadecimal; [1 mark]

− Both addresses do not change if IP address is static; [1 mark]

IP address & MAC addresses

− An IP address is assigned by the network/router/ISP, A MAC address is assigned by the manufacturer; [1

mark]

− An IP address can be changed (if dynamic), MAC address cannot be changed; [1 mark]

− IP address has 4/8 groups of values, MAC address has 6 groups/pairs of values; [1 mark]

− IP address is 32-bit/128-bit, MAC address is 48-bit; [1 mark]

− IP address does not contain serial number/manufacturer number, MAC address does; [1 mark]

− IP(v4) address is denary and MAC address is hexadecimal; [1 mark]

Identify four events that take place during the fetch-execute cycle

An instruction is fetched from memory • The instruction is then decoded • The decoded instruction is then executed so that the CPU performs continuously • The process is repeated • The program counter is incremented • The instruction is transferred to the MDR • The address of the instruction to be fetched is placed in the MAR

Describe purpose of registers that are used by Von Neumann architecture

MAR // memory address register

Stores the address/location where data

will be read/written/accessed/fetched

// address/location of data/instruction

being processed

// address/location of data/instruction

next to be processed

MDR // memory data register

Stores the data/instruction that is

fetched/read from memory

// stores the data that is to be written to

memory

// stores the data/instruction from the

address in the MAR

// data/instruction next to be processed

Program counter

Stores the address/location of the next

instruction to be run

// stores the address/location of the

current instruction being run

Accumulator

Stores the result of

manipulation/process/calculation

Why is more cores not always better?

Software may be designed to run on 1

core and not multiple cores

// depends on the task(s)

…some tasks cannot be split across

cores

Clock speed also affects speed

// dual core may have a faster clock

speed

// quad-core may have slower clock

speed

…so one task may be run faster/slower

RAM size also affects speed

// Quad-core may have less RAM

// amount of VM being used

Cache size also affects speed

// Quad-core may have less cache

What makes smart watch embedded system?

A smart watch is not a general-purpose

computer

… which means the smart watch has

one/limited/specific/dedicated

function(s)

Smart watch has a microprocessor

… on a single circuit board

It is a computer system that is built

within the watch

Runs firmware

Smart watch has built-in OS // difficult

to change/manipulate the OS/function

Smart watch has few components all

essential to its purpose

Smart watch has specific hardware

required to function i.e.

speaker/headphones

Describe how the CPU and RAM work together to enable the computer to operate

Data stored in RAM

Fetched from RAM by CPU

Where they are executed

Purpose of cache memory

To store instructions / data that is

frequently used / previously used / next

to be used

Data does not need to be fetched from

RAM

Speeds up access

Components of computer table

Draw devices and connections in an office star network

Describe role of switch in office network

To connect the devices together

 Receives data/packets/traffic

 Direct/send data/packets/traffic only

to its destination

 Creates/generates a list of devices

connected to it as it receives signals

 Uses MAC addresses of devices

connected to it

Describe what is meant by a character set

All the characters and symbols that can be represented by a computer system; [1 mark]

Each character and symbol is assigned a unique value; [1 mark]

Explain what is meant by MIDI and MP3

MIDI

− Musical Instrument Digital Interface (file)

− Stores a set of commands/instructions (for how the sound should be played)

− Does not store the actual sounds

− Data in the file has been recorded using digital instruments // produced by synthesizer

− Specifies pitch of the note // specifies the note to be played

− Specifies when each note plays and stops playing // Specifies key on/off

− Specifies duration of the note

− Specifies volume of the note

− Specifies the tempo

− Specifies the type of instrument

− Individual notes can be edited

MP3

− MP3 is a format for digital audio

− MP3 is an actual recording of the sound

− MP3 is a (lossy) compression format

− Recorded using a microphone