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OCR Computer science > Section 1 > Flashcards

Section 1 Flashcards

1
Q

What is hardware?

A

Any physical component that makes up a computer.

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2
Q

What is software?

A

Any program that runs on a computer.

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3
Q

What are the 4 basic components that all computers have?

A

Input device (e.g. mouse), CPU, Output device (e.g. speaker), Main memory

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4
Q

What is main memory also called?

A

RAM = main memory = primary storage = memory

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5
Q

What does secondary storage do?

A

It stores data that is used to perform processing, and data that is generated from processing input.

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6
Q

What is the main idea of the Von Neumann architecture?

A

Holding programs in addition to data in memory, allowing for data to move between the memory unit (main memory) and the processor (CPU).

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7
Q

What did the Von Neumann architecture improve?

A

Previously, programs were hardwired into the computer for specific tasks, and to change the program, you had to change the hardwire. With the Von Neumann architecture, you could change what a computer did by simply loading in a new programe, making it more general-purpose.

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8
Q

What does the CPU do?

A

It executes programs and manages the rest of the hardware in the computer.
It 1. stores and retrieves data, 2. processes information and 3. sends signals to different parts of the computer.

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9
Q

What is the fetch stage and which registers does it involve?

A

The CPU fetches an instruction from main memory.
- PC (holds memory address, increments after each stage)
- MAR (temporarily stores address of instruction/ data the CPU has to access)
- MDR (temporarily holds the instruction fetched from main memory)

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10
Q

What is the decode stage and which registers does it involve?

A

The (CU in the) CPU decodes the meaning of the fetched instruction and prepares to execute it.
- CIR (holds the instruction, not data, while the CU decodes it)

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11
Q

What is the execute stage and which registers does it involve?

A

The CPU executes the instruction.
- ACC (stores the results of calculations or operations)
- ALU (performs calculations and logical operations)
- could also involve MAR and MDR if instruction involves fetching from main memory, and could involve PC if the instruction involves a jump.

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12
Q

Which components are in a CPU?

A

CU, ALU and registers (very fast memory locations): MDR, MAR, PC, ACC

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13
Q

What is the function of the CU?

A

The CU coordinates all the activities taking place inside the CPU.
1. It controls the execution of instructions in the correct sequence.
2. It decodes instructions
3. It regulates and controls processor timing using regular pulses from the system clock
4. It sends and receives control signals to and from other devices within the computer.

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14
Q

What is the function of the ALU?

A

It carries out logical operations (and, or, not), shift operations (binary shifts) and arithmetic operations (+-*/)

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15
Q

What does the MAR do?

A

It holds the memory address of the instruction or piece of data to be fetched or stored.

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16
Q

What does the MDR do?

A

It holds data or a program instruction temporarily when it is fetched from memory or is to be sent to memory.

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17
Q

What does the PC do?

A

IT holds the memory address of the next instruction to be processed.

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18
Q

What does the ACC do?

A

It holds the results of operations carried out in the ALU.

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19
Q

What are the factors affecting a CPU’s performance?

A

Clock speed, cache size and number of cores.

20
Q

What is clock speed?

A

How fast the CPU can process instructions. It’s measured in hertz (Hz), which tells you how many cycles (or ticks) the CPU can complete per second.

21
Q

What bottlenecks could potentially slow the CPU down?

A
  • slow RAM
  • slow/ full HDD/ SSD
  • slow cache
22
Q

What is cache memory?

A

A storage area near the CPU that is very fast yet small and expensive, and allows the CPU to access data that is frequently used, which speeds up processor speed as the CPU does not have to access main memory as often.

23
Q

What are the different levels of cache?

A
  • Level 1 cache (extremely fast but small, 2-64KB)
  • Level 2 cache (fairly fast and medium sized, 256KB-2MB)
  • some CPUS have level 3 data cache
24
Q

What is parallel processing?

A

A CPU having more than one core, so that two or four instructions can be executed simultaneously.

25
Q

What are the advantages and limitations of parallel processing?

A

Advantages: allows the PC to execute many tasks at the same time, multi-tasking.
Limitations: Instructions have to be executed in a particular order, so having more cores doesn’t mean a faster processor if the program isn’t designed to be used by multiple cores.

26
Q

What is an embedded system?

A

A small computer built into a piece of equipment designed to perform a specific function. (e.g. fridges, microwaves)

27
Q

What are the characteristics of an embedded system?

A
  • The program that controls the equipment is written in simple, machine-efficient language and is stored in ROM.
  • Limited OS: held in ROM, can only run one application
  • very simple or no user interface: e.g. buttons, knob
28
Q

What is offline storage?

A

Storage devices that can be stored away from the computer. Portable hard disk drives.

29
Q

What is RAM?

A

A temporary storage location where instructions and data used to run a program currently being executed are temporarily stored, to increase access speed to information required from a hard disk.

30
Q

What is virtual memory?

A

Using hard drive space (HDD/ SSD) as if it were RAM, to provide more additional space when main memory isn’t large enough to store the whole of a large program. Stores the part of the program that isn’t currently being executed, and sections of data are swapped to and from RAM and virtual memory depending on whether they are being executed.

31
Q

What is the bootstrap loader?

A

A small program that loads the OS into main memory.

32
Q

Which components are volatile?

A

HDD and SSD are non-volatile and are designed for long-term storage of memory, whereas RAM is volatile as it is designed as a temporary storage for programs that are currently being run.

33
Q

What is ROM?

A

Non-volatile, read-only memory that is typically used to store the bootstrap loader/ (NOT the OS unless it is an embedded system). It is not considered secondary storage, unlike HDDs/ SSDs.

34
Q

What is secondary storage?

A

Non-volatile storage that can hold a relatively large amount of data for long periods of time, used to store files such as music, videos, games etc. Relatively inexpensive and larger than RAM, but has a relatively slower access speed.

35
Q

What are features used to compare secondary storage?

A

Capacity, speed, portability, durability, reliability, cost

36
Q

What are HDDs?

A

Magnetic devices that read data with a moving head inside the disk drive.

37
Q

What are the disadvantages of HDDs?

A
  • magnetic head is vulnerable to magnetic field
  • slower to read/ write due to moving head
  • easier to damage due to moving part
  • less portable
38
Q

What are the advantages of HDDs as compared to SSDs?

A

They have huge capacities, and are suitable for desktop purposes.

39
Q

What are SSDs?

A

A type of storage device used to store data in digital form, using flash memory.

40
Q

What are the advantages of SSDs as compared to HDDs?

A
  • more reliable due to no moving parts
  • lighter
  • faster access times as they don’t have to wait for the head to move/ drive to spin
  • lower power consumption
  • much cooler
  • very thin due to lack of moving parts
  • suitable for laptops/ mobile devices
41
Q

Where are SSDs found?

A

In smaller mobile devices such as cameras, laptops and mobile phones. In memory sticks (pen drives) and memory cards.

42
Q

Where are HDDs found?

A

Magnetic tapes used in data backup. Desktop devices.

43
Q

What are optical devices?

A

Devices that store memory by being written to and read from with lasers.

44
Q

What types of optical media are there?

A

CD, DVD, Blu-ray disks.

45
Q

What formats do CDs come in?

A

CD-ROM (read-only)
CD-R (recordable)
CD-RW (rewritable)

46
Q

Which is the best type of optical storage device?

A

Blu-rays are the cheapest in relation to their storage size. They are also the fastest and have the largest storage spaces, and have by far the longest life expectancies. Essentially they replace DVDs and CDS.

OCR Computer science (2 decks)

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