Manufacturers often advertise computers as a particular amount of memory, attempting to entice the consumer into buying the latest, greatest models. Computers possess more than one kind of memory and two kinds of main memory, necessitating that you understand the concepts and definitions of computer memory to make the best choices when researching computers.
Random Access Memory
Perhaps the more well-known of the two types of main memory, your computer can modify RAM's contents. RAM holds the contents of a program currently in operation and follows specific instructions for its operation, sometimes relayed by the CPU. RAM also holds information necessary for the operation of the computer while powered on, such as a computer's operating system. When a program terminates, the CPU no longer holds that program's information to open up the memory for other programs. The more RAM a computer possesses, the faster it can run programs and the more programs it can run at once.
Read Only Memory
Read Only Memory, or ROM, when used as main memory plays a vital role in a computer's startup and basic operation. Typically containing basic hardware information for all the pieces of your computer, ROM performs several basic checks on hardware before loading the first section of a computer's operating system to RAM. At this point, ROM hands over its role in computer startup to RAM and continues to run in the background enabling the use of hardware, such as a monitor or keyboard. When ROM shows up as secondary memory, it's typically in the form of a CD-ROM or DVD-ROM.
Forms of Main Memory
While the functions of main memory remain basic, many variations of the hardware exist on the market today. As main memory, ROM shows up as a computer's BIOS, or Basic Input Output System. All BIOS chips contain information allowing use of the keyboard, monitor, drives. Very few BIOS chips have the option for rewriting but some models use electrical currents to erase information, such as Electrically Erasable Programmable Read Only Memory, or EEPROM. On the other hand, RAM comes in many variations and remains completely rewritable and modifiable. Check with your computer's manual to determine what type of RAM your computer can use.
Main Memory Vs. Secondary Memory
You must understand the distinction between main memory and its counterpart, secondary memory, to have a complete understanding of main memory itself. Physically, main memory possesses a smaller size and as compared with secondary memory, which you can often remove from a computer. Main memory performs faster than secondary memory but also tends to cost more money. Main memory consists of silicon chips while secondary memory exists as hard drives and flash drives, for example. Most important, RAM cannot hold its information long-term, losing it once you cut power to the computer. You can't typically modify ROM and can't store personal information on it. Secondary memory retains its contents once you cut power, making it necessary for files and other information stored for the long-term.