RAM Random access memory, or RAM for short, is active during the processing function. RAM is often referred to as “temporary memory.” RAM consists of electronic circuits on the motherboard that temporarily hold programs and data while the computer is on. Each circuit has an address that is used by the microprocessor to transmit and store data. When the computer is off, RAM is empty.

RAM RAM is constantly changing as long as the computer is on. For example, if you are writing a paper, the word processing program that you’re using is temporarily copied into RAM so the microprocessor can quickly access the instructions that you’ll need as you type and format your paper. The characters you type are also stored in RAM, along with the many fonts, special characters, graphics, and other objects that you might use to enhance the paper. A microcomputer with 128 MB of RAM can temporarily store over 128 million characters at any one time. Many microcomputers are said to be “expandable,” meaning that additional RAM can be added to the computer.

Virtual Memory When you are multitasking, the processing memory requirements can exceed the amount of available RAM. If this occurs, today’s microcomputer software can automatically use space on your computer’s storage devices to simulate RAM. This extra memory is called virtual memory. Virtual memory is much slower than RAM, however. Therefore, expanding the RAM capacity of a microcomputer is preferable to using virtual memory.

ROM Read-only memory, or ROM, is a set of electronic circuits permanently installed on the motherboard by the computer’s manufacturer. ROM, sometimes called “permanent memory,” is the permanent storage location for the instructions that the computer uses when you turn it on. That is, when the computer is turned on, the set of instructions in ROM checks all the computer system’s components to make sure that they are working and then activates the essential software that controls the processing function. The activities that occur between the moment you turn on the computer and the moment you can actually begin to use the computer are called the boot process. Although a computer’s RAM capacity is typically expandable, you cannot add to the ROM capacity.

CMOS Memory Complementary metal oxide semiconductor, or CMOS, memory is also activated during the boot process. A small rechargeable battery powers CMOS so that its contents will be saved even when the computer is turned off. CMOS memory is often referred to as “semipermanent memory.” Unlike ROM, which cannot be changed, CMOS must be changed every time you add hardware to or remove hardware from your computer system. Most of today’s computers have a “plug-and-play” feature that automatically updates CMOS if you install new hardware such as a new hard drive or printer.

CMOS Memory CMOS holds several critical computer configuration settings, including those listed below. Date and time RAM capacity System performance parameters Power management settings Hardware passwords Configuration parameters for integrated peripherals (storage drives, monitor, keyboard, mouse, printers, …)