3.4 Computer Systems (hardware, storage)

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

Data in remote location Need internet, secondary

• 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

• 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

Pri: main memory in computer, volatile, directly accessible by CPU Sec: permanent store, external device, non volatile, CPU cannot access

Software that manages operation of computer Operating system System utility ( encryption, compression, anti virus)

Perform tasks for user, separate from computer system Word processor, movie making, spreadsheet, presentation software - generic

Generic Proprietary: MS word, Adobe photoshop Off the shelf: accessible by public Bespoke/custom: made for specific client

Virtual machine User interface Memory, input output device management File security management

Eng style commands in high Assembly Lang Uses mnemonic codes / machine code in binary Ultimately they all have to translate into machine code

Interpreter(line by line) and compiler(all at once): high Lang to machine code Assembler: assembly Lang to machine code

Closer to human language Programmer writes easier

Easier to read write cause Eng,ish style commands Portable Must be translated to machine code

Control embedded systems Must use instruction set by processor Require close attention to detail

Pre defined tasks, specific requirements Often includes interface to task specific hardware , with own RAM/ROM Non em has many more functions less limits

Low cost Slower processor but simplified Low power consumption for low cost

Modern car Digital alarm clock, watch, microwave oven, refrigerator, TV, central heating system, burglar alarm

In aeroplanes, mission-critical system made sure to work if anything happens, FAIL SAFE systems built intakes over the main when needed

Stores data digitally Uses laser beams Light, portable cheap, reliable Fragile, easily damaged, storage limited, needs drive to read data

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

Optical discs Magnetic hard drive Cloud storage SSD

Persistent store bits as electrical charge Small compact portable, high capacity, reliable Expensive, short life span

binary data is represented by tiny magnetised regions read/write head moves while disk spins round a whole sector is read in one go

more pulses a second then more fetch-execute cycles higher clock speed = more instructions can start per second