Random Access Memory (RAM) is the best known form of Computer Memory. The Read and write (R/W) memory of a computer is called RAM. The User can write information to it and read information from it.With Ram any location can be reached in a fixed ( and short) amount of time after specifying its address.
The RAM is a volatile memory, it means information written to it can be accessed as long as power is on. As soon as the power is off, it can not be accessed. so this mean RAM computer memory essentially empty.RAM holds data and processing instructions temporarily until the CPU needs it.
RAM is considered “random access” because you can access any memory cell directly if you know the row and column that intersect at that cell. RAM is made in electronic chips made of so called semiconductor material, just like processors and many other types of chips. In RAM, transistors make up the individual storage cells which can each “remember” an amount of data, for example, 1 or 4 bits – as long as the PC is switched on. Physically, RAM consists of small electronic chips which are mounted in modules (small printed circuit boards). The modules are installed in the PC’s motherboard using sockets – there are typically 2, 3 or 4 of these.
There are two basic types of RAM
Dynamic RAM: loses its stored information in a very short time (for milli sec.) even when power supply is on. D-RAM’s are cheaper & lower.
Similar to a microprocessor chip is an Integrated Circuit (IC) made of millions of transistors and capacitors.
In the most common form of computer memory, Dynamic Memory Cell, represents a single bit of data. The capacitor holds the bit of information – a 0 or a 1. The transistor acts as a switch that lets the control circuitry on the memory chip read the capacitor or change its state. A capacitor is like a small bucket that is able to store electrons. To store a 1 in the memory cell, the bucket is filled with electrons.
To store a 0, it is emptied. The problem with the capacitor’s bucket is that it has a leak. In a matter of a few milliseconds a full bucket becomes empty. Therefore, for dynamic memory to work, either the CPU or the Memory Controller has to come along and recharge all of the capacitors holding it before they discharge. To do this, the memory controller reads the memory and then writes it right back. This refresh operation happens automatically thousands of times per second.