Primary memory, or storage, is the area of a computer from which the processor can access data quickly. It is active only while the computer is switched on. Primary memory is much smaller than the secondary, more permanent memory, such as a hard disk, CD-ROM or DVD.
Originally called core storage, primary memory is a term that originated in the days of big mainframe computers to distinguish it from secondary storage, which required input and output operations for storing and retrieving data. With the arrival of personal computers, primary memory became known as RAM--random access memory.
Content of the Primary Memory
RAM typically contains portions of the operating system as well as applications and data in active or frequent use. The part of the operating system stored in the primary memory is called the kernel. It is the first part that loads when the computer is turned on, and it stays there until the computer is turned off. Parts of the programs that are used when the computer is on, like text or a spreadsheet, also stay in the RAM.
Primary Memory Capacity
In deciding how much memory you need, follow a simple rule: the more, the better. Larger primary memory allows the computer to perform operations faster. RAM capacity is measured in gigabytes. Most computers, as of 2010, come with a 2 gig RAM, which can be easily expanded to 4 gigs.