1.1 System Architecture

Question 1

Hardware

Answer 1

Physical stuff in a computer system, e.g. CPU, keyboard, etc.

Question 2

Software

Answer 2

Programs that a computer system runs, e.g. operating systems, games, etc.

Question 3

Embedded systems

Answer 3

Computers built into other devices, usually as control systems. E.g. Dishwashers, microwaves.
- Easier to design
- Cheaper to produce
- More efficient at their task than general-purpose systems

Question 4

What are the four common CPU components?

Answer 4

• Control Unit (CU)
• Arithmetic Logic Unit (ALU)
• Cache
• Registers

Question 5

Central Processing Unit (CPU)

Answer 5

Where a computer processes all data and instructions

Question 6

Control Unit (CU)

Answer 6

Controls the flow of data in and out of the CPU. Manages the fetching, decoding and execution of instructions

Question 7

Arithmetic Logic Unit (ALU)

Answer 7

Does basic calculations, binary shifts and logic operations

Question 8

Cache

Answer 8

Stores regularly use data for quick access. Low capacity and expensive. 3 levels of cache memory: L1 -> L3, decreasing speed but increasing capacity

Question 9

Registers

Answer 9

Temporarily hold small amounts of data. Very quick to read/write to

Question 10

What are the 3 factors affecting CPU performance?

Answer 10

• Number of cores
• Clock speed
• Cache size

Question 11

How does the number of cores affect CPU performance?

Answer 11

• Each core process data independently
• More cores -> more instructions carried out per second
• Some software takes advantage of multicore processing

Question 12

How does clock speed affect CPU performance?

Answer 12

Number of instructions a single processor core can carry out per second

Question 13

How does cache size affect CPU performance?

Answer 13

Larger CPU cache -> faster access to more data

Question 14

What is in the Von Neumann Architecture?

Answer 14

• Control unit -> Program counter (PC)
• Arithmetic Logic Unit -> Accumulator
• Registers -> Memory Address Register (MAR) and Memory Data Register (MDR)
• Memory
• Input and output device

Question 15

Program Counter (PC)

Answer 15

Holds the memory address of the instruction for each cycle

Question 16

Memory Address Register (MAR)

Answer 16

Holds any memory address about to be used by the CPU. The address could point to data or an instruction

Question 17

Memory Data Register (MDR)

Answer 17

Holds the actual data or instruction, either fetched from memory or waiting to be written to memory

Question 18

Accumulator

Answer 18

Stores intermediate results of calculations in the ALU

Question 19

Fetch (FDE cycle)

Answer 19

• Memory address copied from the PC to the MAR
• Instruction copied from memory to the MDR
• PC incremented to point to the next instruction

Question 20

Decode (FDE cycle)

Answer 20

• Instructions in the MDR decoded by the CU
• CU prepares for the next step, e.g. loading values into the MAR or MDR

Question 21

Execute (FDE cycle)

Answer 21

Decoded instruction carried out. E.g.
- Load data from memory
- Write data to memory
- Do calculation or logic operations (using the ALU)

Question 22

Primary storage

Answer 22

Memory that the CPU can read/write to quickly, e.g. RAM

Question 23

Volatile

Answer 23

Power is required for the component to retain data

Question 24

Non-volatile

Answer 24

Component retains the data even when the power is turned off

Question 25

Random Access Memory (RAM)

Answer 25

The main temporary memory in a computer
- Volatile memory
- Can be read from and written to
- Programs and files are copied here from secondary storage while in use
- Slower than the CPU cache, but faster than the secondary storage

Question 26

Virtual Memory

Answer 26

• Used when RAM is filled up
• Some data is moved to a location in secondary storage
• Data is moved back to RAM when the CPU needs it
• Data transfer is slower on secondary storage -> slows performance

Question 27

Read Only Memory (ROM)

Answer 27

Main permanent memory in a computer
- Non-volatile memory
- Can only be read from, not written to
- Small amount of memory built into the motherboard
- Contains BIOS (Basic Input Output System) -> instructions needed for the computer to boot up

Question 28

Secondary Storage

Answer 28

Non-volatile storage where programs and data are kept for later use

Question 29

Examples of internal storage

Answer 29

• Optical Disk Drives (ODDs)
• Hard Disk Drives (HDDs)
• Solid State Drives (SSDs)

Question 30

Hard Disk Drives

Answer 30

• High capacity
• Quick access to data
• Moving parts -> will eventually fail
• Stores data magnetically on metal disks
• Can be noisy

Question 31

Solid State Drives

Answer 31

• Medium capacity
• Very quick access to data
• No moving parts
• Use flash memory for faster read/write times
• Usually quiet/silent

Question 32

Examples of external storage

Answer 32

• Flash drives & memory cards
• Optical discs
• Magnetic tape
• External HDDs & SSDs

Question 33

Flash drives & memory cards

Answer 33

Solid-state storage used to expand the capacity of small devices

Question 34

Optical discs

Answer 34

e.g. CDs. Can be read-only, write-once or rewritable

Question 35

Magnetic tape

Answer 35

Used by organisations to store huge amounts of data

Question 36

External HDDs & SSDs

Answer 36

Portable versions of internal storage. Often used for backups

Question 37

What are the 5 functions of an operating system (OS)

Answer 37

• Peripheral management and drivers
• Providing a user interface
• Memory management and multitasking
• File and disk management
• User management

Question 38

Peripheral management and drivers

Answer 38

• Communicate either internal hardware and peripherals connected to the system, using drivers
• Chooses correct drivers for connected hardware on startup
• Installs drivers for new hardware and update drivers automatically

Question 39

Providing a user interface

Answer 39

Allows user to interact with a computer. Different interfaces are designed for different types of user:
- Graphical User Interfaces (GUIs) -> windows, icons, menus and pointers. Designed for everyday users
- Command-Line Interfaces -> text-based and use fewer system resources than GUIs. Used by advanced users