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memory Last modified: Wednesday, February 27, 2008
Internal storage areas in the computer. The term memory identifies data storage that comes in the form of chips, and the word storage is used for memory that exists on tapes or disks. Moreover, the term memory is usually used as a shorthand for physical memory, which refers to the actual chips capable of holding data. Some computers also use virtual memory, which expands physical memory onto a hard disk. Every computer comes with a certain amount of physical memory, usually referred to as main memory or RAM. You can think of main memory as an array of boxes, each of which can hold a single byte of information. A computer that has 1 megabyte of memory, therefore, can hold about 1 million bytes (or characters) of information. There are several different types of memory: RAM (random-access memory): This is the same as main memory. When used by itself, the term RAM refers to read and write memory; that is, you can both write data into RAM and read data from RAM. This is in contrast to ROM, which permits you only to read data. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost. ROM (read-only memory): Computers almost always contain a small amount of read-only memory that holds instructions for starting up the computer. Unlike RAM, ROM cannot be written to. PROM (programmable read-only memory): A PROM is a memory chip on which you can store a program. But once the PROM has been used, you cannot wipe it clean and use it to store something else. Like ROMs, PROMs are non-volatile. EPROM (erasable programmable read-only memory): An EPROM is a special type of PROM that can be erased by exposing it to ultraviolet light. EEPROM (electrically erasable programmable read-only memory): An EEPROM is a special type of PROM that can be erased by exposing it to an electrical charge. See "Tips to Fix a Slow Running Computer" in the Quick Reference section of Webopedia.
Memory Errors, Detection and Correction  Describes the facilities available for doing error detection and correction and discusses what some of the important factors are. This page is from "The PC Guide." PC Mechanic - online guide to computer hardware  Contains overviews, purchasing and installation information for PC motherboards, memory, drives, expansion cards, and power supplies. Also contains links to companies and manufacturers and PC hardware related links. Memory Packaging Describes the types of memory packaging available and the issues involved in selecting and using memory packages and DRAM chips in a PC. This page is from "The PC Guide." Memory Speed, Access and Timing Describes how the system memory works. Includes details on how memory is accessed and important issues related to system timing. This page is from "The PC Guide". Memory Technology Types Describes the main types of memory used in PCs (ROM, RAM, SRAM, and DRAM) and how they differ from each other. This page is from "The PC Guide". PC Guide's system memory reference Extensive reference covering the system memory. Covers technology types, memory speed and timing, packaging, error detection and correction, and the logical memory layout. PC memory management Phoenix Technologies, designer of the PhoenixCard Manager Plus, describes the evolution of PC memory management with a description of how this product works within the DOS Protected Mode Services (DPMS). Webopedia Quick Reference: A Guide to System Memory Think deciding what computer to buy can be complicated? Just wait until you need to upgrade your system memory. We go inside Random-Access Memory (RAM) with a special focus on DRAM, which is — for now, anyway — the most common and affordable variety. Webopedia Quick Reference: Common Windows PC Issues Tips to Diagnose and fix a slow running computer. Webopedia's "Did You Know...?" Section Use this Webopedia knowledge section for an in-depth overview of specific technologies and occurrences in the areas of Computer Science, The Internet, and Computer Hardware and Software.	Related Categories Memory Related Terms absolute address address chip C-RIMM EEPROM EPROM main memory MDRAM memory leak NVRAM PROM RAM RDRAM RIMM ROM secondary memory solid state disk virtual memory VRAM