3.4 Computer Systems (hardware, storage) Flashcards
4 types of memory in a computer
Random access memory: volatile from hard drive
Read only memory: non volatile
Cache: fast access, close to CPU volatile
Register: fast access memory, in CPU used in fetch execute cycle
Cloud storage
Data in remote location
Need internet, secondary
Ad of cloud storage
- secure data even if physical damage of computer
- can be accessed anytime anywhere
- affordable, no need to invest in employees IRL
- can collaborate with other users just need internet
Disadvantage of cloud storage 5
- need reliable internet to access
- download + upload speed affected by internet
- user don’t have full control over their data
- data security privacy issues
- host company may suffer security breach
Primary v secondary memory
Pri: main memory in computer, volatile, directly accessible by CPU
Sec: permanent store, external device, non volatile, CPU cannot access
Define system software + eg
Software that manages operation of computer
Operating system
System utility ( encryption, compression, anti virus)
Application software define + eg
Perform tasks for user, separate from computer system
Word processor, movie making, spreadsheet, presentation software - generic
4 types of application software
Generic
Proprietary: MS word, Adobe photoshop
Off the shelf: accessible by public
Bespoke/custom: made for specific client
Operating system function
Virtual machine
User interface
Memory, input output device management
File security management
High vs low level languages
Eng style commands in high
Assembly Lang Uses mnemonic codes / machine code in binary
Ultimately they all have to translate into machine code
Three types of generator
Interpreter(line by line) and compiler(all at once): high Lang to machine code
Assembler: assembly Lang to machine code
Why is high level language preferred
Closer to human language
Programmer writes easier
Ad and disad of high level Lang
Easier to read write cause Eng,ish style commands
Portable
Must be translated to machine code
Ads and disad of low level Lang
Control embedded systems
Must use instruction set by processor
Require close attention to detail
Embedded system vs not
Pre defined tasks, specific requirements
Often includes interface to task specific hardware , with own RAM/ROM
Non em has many more functions less limits
Embedded system costs
Low cost
Slower processor but simplified
Low power consumption for low cost
Uses of embedded system 3
Modern car
Digital alarm clock, watch, microwave oven, refrigerator, TV, central heating system, burglar alarm
Critical embedded systems
In aeroplanes, mission-critical system made sure to work if anything happens, FAIL SAFE systems built intakes over the main when needed
Optical discs define
Ads disad
Stores data digitally
Uses laser beams
Light, portable cheap, reliable
Fragile, easily damaged, storage limited, needs drive to read data
Magnetic disks / HDD - description +
Pros and cons
Retrieve info by rotating disks on reading head
High capacity, cheap, reliable, widely available
Heavy, not portable, moving parts may fail due to motors, not easily repaired
Secondary storages 4
Optical discs
Magnetic hard drive
Cloud storage
SSD
SSD Solid state drive
Ad disad
Persistent store bits as electrical charge
Small compact portable, high capacity, reliable
Expensive, short life span
How is data stored on magnetic hard disk
binary data is represented by tiny magnetised regions
read/write head moves while disk spins round
a whole sector is read in one go
how does clock speed affect CPU performance
more pulses a second then more fetch-execute cycles
higher clock speed = more instructions can start per second
