The memory of a computer is a set of electronic components capable of temporarily storing data to remember and retrieve that information.
It is characterized by:
- The capacity (in bits) representing the overall volume of information that the memory can store,
- The access time, corresponding to the time interval between the read / write request and the availability of the data.
- The bit rate (in bits/second) defining the volume of information exchanged per unit of time.
- The non-volatility characterizing the ability of a memory to preserve the data when it is no longer electrically powered.
We distinguish different types of memory
- Dead Memory
- Flash memory
- RAM = RAM = Random Access Memory.
- This is the main memory of the system, it comes in the form of small cards (called memory cards) which are fixed on the motherboard of which each bar has a capacity (a size) expressed in megabytes or gigabytes (abbreviated Mo and GB).
The processor uses this RAM to store all kinds of data it needs quickly.
It is a volatile memory, that is to say, that it can store data only when it is electrically powered.
When the computer is turned off, this memory is erased. That's why it's important to back up our data on the hard drive (or whatever).
The read-only memory = ROM = Read Only Memory.
It is the memory which does not lose its contents when it is not electrically fed
This type of memory allows in particular to keep the data necessary for the starting up of the computer (case of ROMA BIOS).
The access time in the read-only memory is of the order of size (greatness) of 150 nanoseconds compared with an access time of about 10 nanoseconds for the random access memory. To accelerate the treatment(processing) of the information, the data stored in the read-only memory are generally copied in a random access memory before being handled(treated).
We call this operation the shadowing.
It is the memory which possesses the characteristics of a random access memory except that the data do not disappear during a putting switched off.
There are two big families of flash memories:
- · memory cards: they are intended for the small materials (equipment’s) as the digital cameras or the mobile phones.
- · The electronic records (disks): they are static units of storage intended to replace gradually hard disks, often called records (disks) SSD.