Random Access Memory

12. RAM (random access memory) is a temporary holding area for data, application program instructions, and the operating system. RAM is usually several chips or small circuit boards that plug into the system board within the computer’s system unit. RAM is the “waiting room” for the computer’s processor. It holds raw data waiting to be processed as well as the program instructions for processing that data.

13. RAM also holds the results of processing until they can be stored more permanently on disk or tape, it also holds data and application software instructions, operating system instructions that control the basic functions of a computer system. These instructions are loaded into RAM every time you start your computer, and they remain there until you turn off your computer.

14. People sometimes tend to confuse RAM and hard-disk storage, maybe because both components hold data, because they typically are “hidden” inside the system unit, or because they can both be measured in gigabytes. To differentiate between RAM and hard-disk storage, remember that RAM holdsdata in circuitry that’s directly connected to the system board, whereas hard-disk storage places data on magnetic media. RAM is temporary storage; hard-disk storage is more permanent. Besides, RAM usually has less storage capacity than hard-disk storage.

15. In RAM, microscopic electronic parts, called capacitors hold the bits that represent data. You can visualize the capacitors as microscopic lights that can be turned on and off. A charged capacitor is “turned on” and represents a”1” bit. A discharged capacitor is “turned off” and represents a “0” bit. Each bank of capacitors holds eight bits – one byte of data. A RAM address on each bank helps the computer locate data as needed, for processing.

16. Each RAM location has an address and uses eight capacitors to hold the eight bits that represent a byte. See Figure 1:

Fig. 1: The way RAM represents different characters

17. In some respects, RAM is similar to a chalkboard. You can use a chalkboard to write mathematical formulas, erase them, and then write an outline for a report. RAM contents can be changed just by changing the charge of the capacitors.Unlike disk storage, most RAM is volatile, which means it requires electrical power to hold data. If the computer is turned off or the power goes out, all data stored in RAM instantly and permanently disappears.

18. Today’s personal computer operating systems are quite adept at allocation RAM space to multiple programs. If a program exceeds its allocated space, the operating system uses an area of the hard disk, called virtual memory, to store parts of programs or data files until they are needed. By selectively exchanging the data in RAM with the data in virtual memory, your computer effectively gains almost unlimited memory capacity.

19. RAM components vary in speed, technology, and configuration. RAM speed is often expressed in nanoseconds or megahertz. One nanosecond (ns) is 1 billionth of a second. In the context of RAM speed, lower nanosecond ratings are betters because it means the RAM circuitry can react faster to update the data it holds. For example, 8 ns RAM is faster than 10 ns RAM. RAM speed can also be expressed in MHz (millions of cycles per second). Just the opposite of nanoseconds, higher MHz rating means faster speeds. For example, 533 MHz RAM is faster then 400 MHz RAM.

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