What are 3 differences between RAM and ROM?
- RAM is volatile, ROM is non-volatile
- RAM can be read and written into, ROM can only be read
- RAM is the main memory for a computer, ROM tells CPU how to boot up (BIOS)
What is in the main memory?
all the data, files and programs are stored while they’re being USED
What happens to software applications, documents and files once opened?
They are copied from secondary storage to RAM and stay in RAM until they are closed
Where is ROM?
ROM comes on a small, factory-made chip built into the motherboard.
What do the CPU and ROM do when the computer is booted up?
CPU read instructions from ROM, telling the CPU to perform self-checks and set up the computer.
How much ROM and RAM does a non-embedded system have?
- usually have much more RAM than ROM
- often need to write data to main memory
- ROM usually only used for Basic Input Output System
- ROM and RAM stored on motherboard away from CPU
How much ROM and RAM does an embedded system have?
- usually more ROM than RAM
- don’t write much data to main memory
- don’t tend to have secondary storage/ ROM used to store all programs
- ROM and RAM often stored on same chip as CPU-reduce physical space and cost
What is secondary storage?
non-volatile storage that stores all data (eg. applications, files, the OS) when they are not in use.
It isn’t directly accessible to the CPU
What are the 4 types of secondary software?
- magnetic hard disks
- solid-state drives
- optical discs
- cloud storage
How do magnetic hard disks work?
Magnetic HDD uses moving read/write heads that contain electromagnets.
The disks surface contains iron particles that can be given a polarity.
Data is stored in thin bands called tracks, within sectors in between each track.
The head can move to any sector to read or write
adv of MHDD (4)
- very large storage capacity
- faster than optical disk
- non-volatile
- cheaper per MB
disadv of MHDD (4)
- moving parts can fail
- easily damaged
- uses a large amount of power
- can be noisy
How is a solid-state disk different to HDD?
SSD contain no moving parts and don’t rely on magnets
adv of SSD (6)
- reads faster than normal hard drives
- lightweight
- durable
- free from mechanical issues
- less power than magnetic drives
- silent to use
disadv of SSD (2)
- limited storage capacity
- costs more per MB
How do optical discs work?
Use reflective light to read data.
A laser burns pits and lands into the OD’s surface changing its reflective properties, making microscopic pits and lands.
To read off of the disk, the laser works at a lower read measuring light reflection.
The laser light reflection is detected by a sensor, assigning 1 for a pit and 0 for land.
Examples od OD’s include CDs, DVDs and Blu-ray.
adv of OD (3)
- easy to store and carry
- read in many devices
- if looked after, long-lasting
disadv of OD (4)
- disks are write-once, data is permanent
- requires special drives to r/w
- expensive per MB
- easily broken/scratched
What is cloud storage?
Cloud storage is a service where files can be uploaded to a remote server via the internet
Adv of cloud (3.5)
- unlimited storage capacity
- automatic back-up
- universal access (across space and devices)
disadv of cloud
- requires a reliable internet connection
- slower than accessing locally stored data
- the user is not in control of what happens to the data
