ROM:Read Only Memory,it cannot be erased or changed* and contains all about that computer and programs pre-installed for the functioning of CPU
RAM:Random Access Memory, is the memory where application are opened.Is much faster than hard disk but it has a defect:As soon as the computer is switched off,the data inside RAM is lost*.
Ways of storing data permanently:
The Hard Disk:is the main internal disk composed by magnetised discs divided into sectors that are read by a small arms while discs spin,has a large capacity.
Optical discs:are all that discs that store data on the reflective surface* and requires a laser beam (commonly inside the disc drive)that reads the change in position of the reflected beam. There are two types:
.CDs(Compat Discs):700MB of space that can be only read
.CD-R (Recordable)*:can be written on only once
.CD-RW (Re-Writable)*:can be erased and rewritten
DVDS: same functioning of CDs but can hold 9.4 GB of data,other variations are DVD-ROM,R and RW but the most efficient is the Blu-ray with 50 GB of space.
Memory sticks: use a technology called "flash memory" to store up to 128 GB in very small devices. It can be written or read with computer's USB port,is the most common type and soon will replace the other two types*.