Memory

Computer memory is any physical device capable of storing information temporarily or permanently. For example, Random Access Memory (RAM), is a type of volatile memory that is stores information on an integrated circuit, and that is used by theoperating system, software, hardware, or the user. Below is an example picture of a 512MB DIMM computer memory module.

Volatile vs. non-volatile memory

Memory can be either volatile and non-volatile memory. Volatile memory is a temporary memory that loses its contents when the computer or hardware device loses power. Computer RAM is a good example of a volatile memory and is why if your computer freezes or reboots when working on a program you lose anything that hasn't been saved. Non-volatile memory, sometimes abbreviated as NVRAM, is memory that keeps its contents even if the power is lost. EPROM is a good example of a non-volatile memory.

Memory is not disk storage

It is very common for new computer users to be confused by what parts in the computer are memory. Although both the hard drive and RAM are considered memory, it is more appropriate to refer to RAM as "memory" or "primary memory" and a hard drive as "storage" or "secondary storage" and not memory.

When a program such as your Internet browser is open, it is loaded from your hard drive and placed into RAM, which allows that program to communicate with the processor at higher speeds. Anything you save to your computer such as a picture or video is sent to your hard drive for storage.

When someone asks how much memory is in your computer, it is likely between 1GB and 8GB of Random Access Memory (RAM) and several hundred Gigs of hard disk drive memory (storage). In other words, You will almost always have more hard drive space than RAM.

Memory is the electronic holding place for instructions and data that your computer's microprocessor can reach quickly. When your computer is in normal operation, its memory usually contains the main parts of theoperating system and some or all of the application programs and related data that are being used. Memory is often used as a shorter synonym for random access memory (RAM). This kind of memory is located on one or more microchips that are physically close to the microprocessor in your computer. The more RAM you have, the less frequently the computer has to access instructions and data from the more slowly accessed hard disk form of storage.

Memory is sometimes distinguished from storage, or the physical medium that holds the much larger amounts of data that won't fit into RAM and may not be immediately needed there. Storage devices include hard disks, floppy disks, CD-ROM, and tape backup systems. The term sauxiliary storage, auxiliary memory, and secondary memory have also been used for this kind of data repository.

Additional kinds of integrated and quickly accessible memory are read-only memory (ROM), programmable ROM (PROM), and erasable programmable ROM (EPROM). These are used to keep special programs and data, such as the basic input/output system, that need to be in your computer all the time.

TABLE OF CONTENTS

• Introduction

1. Main memory
2. Auxiliary memory
3. Memory hierarchy

Computer memory, device that is used to store data or programs (sequences of instructions) on a temporary or permanent basis for use in an electronic digital computer. Computers represent information in binary code, written as sequences of 0s and 1s. Each binary digit (or “bit”) may be stored by any physical system that can be in either of two stable states, to represent 0 and 1. Such a system is called bistable. This could be an on-off switch, an electrical capacitor that can store or lose a charge, a magnet with its polarity up or down, or a surface that can have a pit or not. Today capacitors and transistors, functioning as tiny electrical switches, are used for temporary storage, and either disks or tape with a magnetic coating, or plastic discs with patterns of pits are used for long-term storage.