Flashcards · 2210 · Topic 3

Hardware flashcards

23 cards on Topic 3, subtopics 3.1 to 3.4. Pick a subtopic or study them all.

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3.1 Computer architecture

What is the role of the CPU?: To process instructions and data by carrying out the fetch-decode-execute cycle. It contains the ALU, the control unit, registers and buses.
Which register holds the address of the next instruction, and which holds the instruction being decoded?: The program counter (PC) holds the address of the next instruction. The current instruction register (CIR) holds the instruction being decoded and executed.
MAR vs MDR: The memory address register holds the address of the memory location being read or written. The memory data register holds the data or instruction being transferred to or from that location.
Which bus is one-way, and what do the three buses carry?: The address bus is one-way (CPU to memory) and carries addresses. The data bus carries data and instructions both ways. The control bus carries control signals such as read and write.
Trace the fetch-decode-execute cycle: Fetch: PC → MAR; instruction from RAM → MDR → CIR; PC incremented. Decode: the CU interprets the instruction in the CIR. Execute: the instruction is carried out, e.g. the ALU calculates and the result goes to the ACC.
Why does a larger cache improve CPU performance?: Cache is fast memory close to the CPU that holds frequently used data and instructions, so the CPU fetches them from RAM less often.
Give three examples of embedded systems: Any three of: a washing machine controller, a car engine management system, a security alarm, a lighting system, a vending machine, a microwave. Each performs one dedicated function.

3.2 Input and output devices

Name the three types of touch screen on the syllabus: Resistive, capacitive and infra-red.
Name two types of printer and two types of projector on the syllabus: Printers: inkjet and laser (also the 3D printer). Projectors: digital light processing (DLP) and LCD.
Which sensor would you use in a greenhouse to monitor: warmth; air wetness; soil wetness; brightness?: Temperature sensor; humidity sensor; moisture sensor; light sensor.
What do a pH sensor, a flow sensor and a level sensor measure?: pH sensor: acidity or alkalinity. Flow sensor: the rate at which a liquid or gas moves. Level sensor: how full a container is.
Why must a scenario answer name a specific sensor?: The mark is for naming the sensor and what it measures, e.g. "a proximity sensor to detect nearby obstacles", not just "a sensor".

3.3 Data storage

Why does a computer need both RAM and ROM?: RAM is volatile, so it cannot keep the start-up instructions when the power is off; it holds programs and data in use. ROM is non-volatile and permanently stores the bootstrap instructions.
Name the three types of secondary storage and an example of each: Magnetic: hard disk drive. Optical: CD, DVD or Blu-ray. Solid-state (flash): SSD, SD card or USB flash drive.
How is data stored on an optical disc?: A laser burns pits into the disc surface; the unchanged areas are lands. When reading, a laser is reflected differently from pits and lands, which are read as binary.
How does solid-state storage hold data?: It uses NAND or NOR flash memory with transistors that have a control gate and a floating gate. Charge trapped in the floating gate represents a 1 or a 0, with no moving parts.
Describe how virtual memory is used: When RAM is full, part of secondary storage is used as an extension of RAM. Pages of data not currently needed are moved out of RAM, and moved back in when needed.
What is cloud storage?: Data stored on remote servers, owned by a third party, and accessed over the internet. It can be reached from anywhere, but depends on a connection and on the provider's physical servers.

3.4 Network hardware

What is the purpose of a NIC?: A network interface card lets a device connect to a network. Each NIC has a unique MAC address.
What two parts make up a MAC address?: A manufacturer code and a serial code. The address is fixed at manufacture and written in hexadecimal.
Static vs dynamic IP address: A static IP address is fixed and does not change. A dynamic IP address is assigned by the network each time the device connects, so it can change.
How do IPv4 and IPv6 addresses differ?: IPv4 uses 32 bits, written as four denary numbers from 0 to 255 separated by full stops. IPv6 uses 128 bits, written as eight groups of hexadecimal digits separated by colons.
Give three roles of a router: It directs data packets to their destination, it can assign IP addresses to devices on the network, and it connects a local network to the internet.