Without getting too technical here, the computer memory stores temporary information for the computer to have easy access to it. The hard drive stores the permanent information. Therefore when you open a program it is loaded to the RAM (Random access Memory) and is stored there while you use it. When you close the program it is saved to the hard drive until you want to use it again.If you are thinking of adding some memory it is important to find out what type of ram your computer has in it so you can match the new piece with its specifications. If you have Pc2100 DDR ram in your computer you should put more PC2100 in the other available slots. It doesn’t matter what size it is, but bigger is better.
SD Ram: Pre- Pentium 1.4Ghz computers usually take either PC100 or PC133. You can pick up this computer memory pretty cheap now. PC133 256mb SD ram is around $20.00.
Pictured are two different sized SD ram chips. They have different dimensions, but they have the same notches on the bottom. Their specs are the same. Both 64mb SD ram Pc 100.
DDR Ram: The more modern PC’s take anything from PC2100 (266MHz), PC2700 (333MHz), PC3200 (400-MHz).
You can get PC2100 256mb ddr ram for around $25.00, which is pictured below. See how the notch is in a different place to the sd ram. This is one way to tell them apart. The stickers on the ram have their specifications and serial numbers.
DDR Ram 2: New computers may be compatible to use this ram.
Both SD ram and DDR ram come in various sizes. Starting from 128mb, 256mb, 512mb, and now 1gig and 2 gigs ram sticks. In the earlier days they were also available in smaller sizes, however now days the bigger sizes are the most popular.
Upgrading your computer memory increases system performance, lets you run more applications, and improve graphics and video editing. It is always an improvement to your computer when you add ram.
Cause of this transfer you can read at this link