2 Flashcards
What is the difference between secondary and primary memory ?
Primary: CPU has direct access to (registers, cache, ROM & RAM)
Volatile ( only on with power)
Fast read/write speed
Secondary: not directly accessible
Non-volatile
Where data is stored when not in use
Slow read/ write speed
Magnetic Hard Disks
Made up of magnetised metal disks spinning .
1 &0 for magnetised and demagnetised
Data is stored in sectors , on tracks.
Read write head on a movable arm accesses these sectors.
Long lasting( but moving parts), cheap, large capacity
Solid state (flash)
Drive: Data stored in electrical circuits, by tapping electrons. (Transistors) Fast read write time. Don’t need defragmentation More long lasting, no heat no moving parts, Silent
Optical discs
Eg: CD, DVD, blue Ray
Pits/ (0)holes are made, the reflected beam from laser read is the data
Low capacity, cheap, portable , slow read/write
What is Cloud storage
Data is uploaded via the internet to a remote server (stored on HDD/SSD) . You pay with a subscription.
Roles of the OS
Communicating with input output devices/ via device driver
Process manager- CPU and it’s time with programs
Providing a platform for applications to run
Memory management- how much RAM a program has access to
File management-read/write/delete
System management- user passwords
Why is secondary storage required?
To store long term
Retains data when no power (non-volatile)
High capacity
What is durability?
How much physical damage it can take without breaking
Put in order , in terms of how quickly data is transferred (speed)
Solid
Magnetic
Optical
What are the shapes for AND, OR,NOT and XOR
And- D
Not-triangle &circle
Or- arrow head
XOR- arrowhead with line, does not accept two trues
How do you calculate the total number of combinations for a truth table?
2 * * number of inputs
Eg:
2* * 3 =8
2**2= 4
Symbols for NOT, OR, AND, NOT OR
Not= line overhead
And = .
Or= +
Not or = circle over +
What are advantages and disadvantages of cloud storage?
:)can be accessed from anywhere,
data can be shared ,
cheap,
provides back up/security
:( need Wi-Fi,
data vulnerable to hackers,