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A level Computer Science > Unit 5 - Computer Organisation and Architecture > Flashcards

Unit 5 - Computer Organisation and Architecture Flashcards

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1
Q

What is a computer system?

A

A computer system is any device which takes in an input, processes it and returns an output.

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2
Q

What are the four components of the CPU (Central Processing Unit)?

A
  • Processor
  • I/O Controllers
  • Address bus, data bus, control bus
  • Main memory (RAM)
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3
Q

What are the components in a processor?

A
  • Control unit
  • ALU (Arithmetic Logic Unit)
  • Registers
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4
Q

Define one of the components of a processor.

A

A register is a special memory cell operating at a very high speed. All arithmetic and logical operations from the ALU take place in registers.

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5
Q

Define another component of a processor.

A

ALU (Arithmetic Logic Unit) is a component of a processor which carries out arithmetic operations involving adding, subtracting, multiplying and dividing. It also carries out logical operations with AND, OR, NOT and XOR gates, as well as shift operations.

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6
Q

What is a bus?

A

Buses are sets of parallel wires connected to each components of the CPU. They use parallel transmission.

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7
Q

Describe the third component of the processor.

A

The control unit is another component of the processor, carrying out the fetch-decode-execute cycle:
The processor fetches an instruction
The instruction is decoded
and finally the instruction is executed.
Each step is synchronized by the system clock.

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8
Q

How does the processor use the buses?

A

When the CPU needs the address of an instruction, it requests the address and memory location in main memory. The address bus responds by sending the address to the CPU. The data bus gives the data of the address to the CPU and control signals are sent by the control bus.

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9
Q

Define an I/O controller.

A

An I/O controller is a controller which provides an interface for input and output devices, interfacing between input and output devices on one side and the processor and computer on the other. Each I/O device has a seperate I/O controller, and the processor will send requests to input and output devices by sending them to the controller. The I/O controller will translate the requests for the devices.

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10
Q

Describe the control bus.

A

The control bus is a type of system bus and component of the CPU. It is bi-directional, meaning that the control signals it transmits, are carried in both directions between components. To ensure no disruption occurs towards the data and address buses, and no conflict occurs, the control bus has control lines, with 8, 16, 32, or 64 bits.

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11
Q

What is the role of the control bus?

A

The control bus’s main purpose is to transmit command, timing or special status information between components.

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12
Q

Describe the data bus.

A

The data bus is another component of the CPU, and although it isn’t bi-directional itself, its data does travel in a bi-directional pathway between components. The width of the data bus is an important factor of overall system performance. This is because if the data bus is 6 bits wide and an instruction is 12 bits wide, then the data bus has to go through main memory twice to fetch the instruction.

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13
Q

What is the address bus?

A

The address bus is another type of bus and component of the CPU, and it transfers the address of an instruction from the processor to the I/O controller and main memory (RAM). The width of the address bus determines the maximum possible memory capacity/addresses; if the width of the address bus is n bits, then the memory addresses are 2^n.

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14
Q

What is a word?

A

In terms of memory addresses, the smallest addressable unit is a word.

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15
Q

What is the stored program concept?

A

The stored program concept is where computers store program instructions and data in main memory, and the processor will fetch each instruction one-by-one, executing them in a sequential order.

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16
Q

Describe the Von Neumann architecture.

A

The Von Neumann architecture is a computer architecture involving program instructions and data being stored together in main memory and a single shared bus.

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17
Q

Describe the Harvard architecture.

A

The Harvard architecture is a computer architecture where program instructions and data are stored seperately in individual memory and different buses. Sometimes this may cause the instructions and data to be stored in unequal amounts or there may be different sized words and memory spaces.

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18
Q

What is the Von Neumann architecture used for?

A

The Von Neumann architecture is commonly used in general purpose computers such as desktop computers, laptops, tablet computers…

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19
Q

What is the Harvard architecture used for?

A

The Harvard architecture is used for Digital Signal Processing (DSP) in embedded computer systems, where speed is emphasized over design.

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20
Q

What is the system clock?

A

The system clock is a part of the processor which regularly signals ON/OFF to help synchronise operations of the processor (ensure the operations all happen at the same time).

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21
Q

Give an example of a general purpose register.

A

An accumulator.

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22
Q

Give the names of the special purpose registers.

A
  • Program Counter (PC)
  • Current Instruction Register (CIR)
  • Memory Address Register (MAR)
  • Memory Buffer Register (MBR)
  • Status Register (SR)
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23
Q

Define the PC.

A

The program counter is a dedicated register which holds the next instruction to be executed.

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24
Q

Define the CIR.

A

The current instruction register is a dedicated register that holds the current instruction.

25
Q

What is the MAR?

A

The memory address register is a dedicated register holding the memory address in main memory, just in case if the processor fetches data from there or stores data there.

26
Q

What is the MBR?

A

The memory buffer register temporarily holds data moving between the processor and main memory.

27
Q

What is the SR?

A

The status register holds information on the current state of operations, also setting flags to identify errors such as carry or overflow errors.

28
Q

Give the steps of the fetch-decode-execute cycle.

A

1) The PC (program counter) contains the address of the next instruction to be executed.
2) The PC copies the instruction into the MAR (Memory Address Register).
3) From the MAR, the instruction is sent to main memory via the address bus.
4) At main memory, the instruction is sent to the MBR (Memory Buffer Register) via the data bus.
5) The instruction is sent to the CIR (Current Instruction Register) from the MBR, and the program counter now points to the next address; it is incremented by 1.
6) Lastly, in the CIR the instruction is decoded and carried out/executed by the ALU (Arithmetic Logic Unit).

29
Q

What is the role of the processor?

A

The role of the processor is to execute instructions from programs stored in main memory (RAM).

30
Q

What is the role of the control unit?

A

The control unit helps coordinate all components so they can all work together to help the processor execute instructions.

31
Q

Give a factor that can affect processing performance.

A

Cache memory is superfast memory which stores the most frequently used data of a processor. It is larger and slower than a register but smaller and faster than RAM (main memory). Typically, more quantities of cache memory can improve processing performance.

32
Q

Describe another factor affecting system performance.

A

The system clock - The faster the clock speed, the faster a computer can fetch, decode and execute instructions. Generally, a system clock can change state billions of times a second.

33
Q

Give a third factor affecting processing performance.

A

Number of cores - Cores are the processing units of a processor. The more cores on a singular chip, the more instructions are executed simultaneously, hence boosting processing speed and power.

34
Q

What is an interrupt?

A

An interrupt is a signal sent to the CPU by either software or hardware.

35
Q

What happens during an interrupt?

A

During an interrupt, the execution of instructions is temporarily halted and furthermore, any contents are temporarily saved in registers. An interrupt service routine is then called to deal with the interrupt, and once the issue is resolved then the fetch execute cycle will resume and values from the register are retrieved.

36
Q

Define an instruction set.

A

An instruction set is the set of possible instructions a processor can carry out.

37
Q

Give some examples of instructions in an instruction set.

A
  • Arithmetic instruction
  • Logical instruction
  • Shift instruction
  • Comparison instruction
  • Branch instruction
  • Data transfer instruction
38
Q

What format are instructions of an instruction set in?

A

As the processor and computer only understand pure binary, all instructions are in the form of pure binary machine code (1s and 0s). The number of bits of an instruction is dependant on the word length of a processor.

39
Q

Give the two components of a machine code instruction.

A
  • Opcode (Operation code)

- Operand

40
Q

Give the two components of the opcode.

A

The opcode contains the actual instruction the processor has to carry out as well as the addressing mode which specifies the location of the operand, searches for the operand’s memory address and checks whether it’s in a register or the actual data.

41
Q

How are the operand and memory address linked?

A

The operand contains a reference in the form of an actual value which can be used as presented, or a memory address where the data used is held, or a register where the data is contained in. The addressing mode (in the form of 2 bits) has to specify the location of the operand through one of the three.

42
Q

What is immediate addressing?

A

Immediate addressing is where the operand is specified as an actual value, and this form of addressing uses the addressing mode 00.

43
Q

What is direct addressing?

A

Direct addressing is where the operand is specified as a memory address location, and this form of addressing uses the addressing mode 01.

44
Q

Give some uses of barcodes.

A
  • Airline baggage tracking
  • Product labelling
  • Parcel delivery
45
Q

How do barcode readers work?

A

Barcode readers use the principle of reflected light; light from a laser is reflected to a pattern on the code then the light intensity is detected.
A black bar absorbs all the light, and is less reflective so it gets a binary reading of 1, while the white bar has a binary reading of 0.

46
Q

Give the names of the two types of barcodes.

A
  • UPC-A/EAN

- Code 128

47
Q

What is the UPC-A/EAN barcode used for?

A

This is used for retail and warehousing, and can only display numerical integers.

48
Q

Describe the use of the Code 128.

A

The Code 128 barcode is used for transport and shipment packing and can represent both letters and numbers.

49
Q

Describe the structure of the UPC-A/EAN barcode.

A

The UPC-A/EAN barcode uses long guard bars to signal the left, centre and right of the barcode. Also, on the left is the manufacture number and the right has the product number and check digit.

50
Q

What is the relationship between the left and right codes of a barcode?

A

The right bar and left bar have the opposite colored bars; e.g. if the left bar had 3 black bars, then the right bar has 3 white bars.

51
Q

What are QR codes?

A

QR (Quick Response) codes are barcodes used on smartphones and tablets that hold certain information or links to websites.

52
Q

Give uses of QR codes.

A
  • Boarding passes for a flight
  • Restaurant coupons
  • Mobile concert tickets
53
Q

How do digital cameras work?

A

The shutter opens to let light onto a CCD (Charged Couple Device) at the back of the lens. Then, millions of tiny sensors (one per pixel) are arranged in a grid on the picture, measuring the light intensity of the photo. Then each pixel is converted to a binary value and the image is stored in the camera’s memory.

54
Q

What is an RFID system?

A

Radio Frequency ID (RFID) system is a wireless system comprised of two components; a transponder and powered receiver.

55
Q

How does the RFID system work?

A

The powered receiver emits radio frequency waves/energy.
The transponder antenna in a bank credit card, mobile phone becomes energized by the radio frequency waves/energy.
In response to this, the transponder sends data to the receiver.

56
Q

Give uses of RFID tags.

A
  • Security checkpoints at airports, shopping malls…
  • Banking and fast-payment systems
  • Shipping and supply chain tracking for goods.
57
Q

What is a passive transponder?

A

A passive transponder is a form of RFID tags where the transponder doesn’t have a power source of its own, instead relying on energy from the receiver. This is commonly found in credit cards, mobile phones…

58
Q

What is an active tag?

A

An active tag is a form of RFID tags, which generates a battery powered beacon which broadcasts a signal up to 300m away. This makes it useful for not placing a good by hand on receivers; control points, shipping and tracking goods…

A level Computer Science (12 decks)

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