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Computer Science HL > 2.1 The CPU + Fetch-Decode-Execute > Flashcards

2.1 The CPU + Fetch-Decode-Execute Flashcards

1
Q

What is the CPU?

A

The internal hardware component that is responsible for processing data and executing the instructions of programs.

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2
Q

What is the ALU?

And what does it do?

A

The arithmetic logic unit.

Performs arithmetic and logical calculations.

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3
Q

What is the CU?

And what does it do?

A

The control Unit organises the order of program instructions.

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4
Q

Name four processes the Control Unit completes:

A

Sends control signals to enable data to be read and written.
Decodes instructions to determine what needs to be done.
Organises sequence of micro-operations
Uses control signals to determine which operation the ALU will carry out.

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5
Q

What is the Clock?

A

The system clock generates a regular pulse to synchronise operations.

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6
Q

What is a clock low?

A

0

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7
Q

What is a clock high?

A

1

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8
Q

What is a rising edge?

A

Low to high

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9
Q

What is a falling edge?

A

high to low

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10
Q

What is a clock period?

A

time between two rising edges

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11
Q

What is a clock cycle?

A

One clock period

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12
Q

Equation for clock rate:

A

Clock frequency (a.k.a. rate or speed) = 1 / clock period

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13
Q

What are registers?

A

Locations of computer memory that provide fast access.

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14
Q

What are general purpose registers?

A

Temporary storage for operation results that need to be accessed again

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15
Q

What are dedicated registers?

A

Registers for a specific purpose.

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16
Q

Name some dedicated registers

A 
Program Counter
Current Instruction Register
Status Register
Memory Address Register
Memory Buffer Register (a.k.a. Memory Data Register)
Accumulator
17
Q

What is PC? And what does it do?

A

The program counter holds the address of the next instruction to be executed.

18
Q

What is the CIR? And what does it do

A

Current Instruction Register, holds the current instruction.

WOW

19
Q

What is the SR? And what does it do?

A

The Status Register stores information about the result of the last instruction. To indicate if an error or exception has occurred to help disable interrupts.

20
Q

What is an error or exception?

A

Result of a calculation that requires further action

21
Q

What is an interrupt?

A

Event outside program that requires attention of processor

22
Q

What is the MAR? And what does it do?

A

Temporarily holds the address of the memory location processor needs to access.

23
Q

What is the Memory Buffer Register and what does it do?

A

The MBR temporarily holds the data that are read from or written to main memory a.k.a. Memory Data Register (MDR)

24
Q

What is the accumulator?

A

Stores the results of any calculation processed by the ALU

25
Q

What is the Fetch-Decode-Execute Cycle?

A

A sequence of steps behind every operation carried out in the computer.

26
Q

What has to occur before the FDE?

A

The program instructions have to be translated into machine code.
And the program instructions have to be loaded from secondary storage into main memory.

27
Q

What happens in the Fetch Part?

A
  • (PC) Program Counter provides address of next instruction
  • This address is copied to memory address register (MAR)
  • Address sent to Main Memory along address bus.
  • Control Unit (CU) sends a signal along control bus.
  • The content stored at the address is sent along data bus to the Memory Data Register (MDR).
  • Data is copied to Current Instruction Register (CIR)
28
Q

What happens in the Decode Part?

A

Control Unit decodes the instruction of CIR

29
Q

What happens in the Execute part?

A

Instruction is executed in the exact sequence of operations necessary for that instruction.

30
Q

What occurs at the end of the cycle?

A

At the end of a cycle the processor checks the status register for an error or exception or interrupt. Before starting the next cycle.

31
Q

What is a data bus?

A

Sends data from the registers to the RAM.

32
Q

What is command line?

A

Text interface on your computer.

33
Q

What is different between Command Line and GUI?

A

GUI lets a user interact with the device/system with the help of graphical elements, like windows, menus, icons, etc.
The CLI, on the other hand, lets a user interact with their device/system with the help of various commands.
Some OS provide their users with only CLI, while some offer both CLI and GUI.

Computer Science HL (25 decks)

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