What is Memory?

Data and program instructions are stored in the electronic circuitry of the computer until it is their turn to be processed. This circuitry area is called memory. It is sometimes called primary storage. Many people confuse memory with disk storage. The media that stores information that is not related to the processor is called storage. Memory refers to the circuits that are directly linked to the processor. This circuit board is called a single in-line memory module (SIMM). It contains three to nine DIP packages. A dual in-line package (DIP) is a memory module that stores 256 kilobytes of data.

The memory chips need to be able to communicate directly with the central processing unit. In some earlier computers, memory was soldered directly onto the motherboard or the logic board. The need for more and more memory for software solutions, requires that memory now be added onto the board through modules. Most computers come with a standard 8 megabytes (8 million bytes) of RAM with room on the logic board to add more memory. The amount that one can add is dependent upon the machine and the manufacturer of the computer.

Types

Basic Types of Memory

Random Access Memory (RAM) **TEMPORARY MEMORY**

• This is the area that the computer system uses to temporarily hold data before and after it is processed. Any data that needs to be processed has to have RAM to process it. RAM gives instructions to the central processing unit. Stored in RAM are program instructions, operating system instructions, and data. Each character that is typed into RAM is held in RAM until it is saved to disk. The RAM also holds program instructions. Your computer disk that holds your word processor can suddenly be turned into RAM so that the word processing function can be achieved. The operating instructions which help control basic computer functions are also loaded into RAM each time the computer is turned on. RAM is very immediate. If the computer is turned off or the power has gone out, and you have not saved your work, everything stored in RAM is lost. That is why it is important to save your work as you go along.It is also called temporary memory, because it is constantly being overwritten and updated with new data.

How much RAM is needed for your computer?

RAM is measured in megabytes. The software that you use is really the measure of how much RAM you need. Most computers have between 4 and 32 megabytes of RAM. To run the typical Windows 95 operating system 8 megabytes of RAM is needed and 16 megabytes (16 million bytes of data) is recommended. When your software requires more RAM than your computer currently has, you can purchase additional RAM to expand the memory capacity. Each computer has a limit to the amount of RAM you can add. Check carefully when buying your computer. RAM is specific for each computer. Check carefully for the correct type, speed and configuration for you computer.

Virtual Memory **DISK BASED MEMORY**

• The computer's ability to use disk storage to simulate RAM. The computer uses space on the hard drive as an extension of RAM. It allow computers to run large programs that do not have enough real memory, and to also run more than one program at a time.
  Disadvantages: reduced performance and any data in virtual memory becomes inaccessible if the power goes off.
  

Read only Memory (ROM) **PERMANENT MEMORY**

• ROM. is a set of chips that contain permanent instructions that helps the computer get ready for processing tasks. When the computer is turned on, the RAM is empty so there is no way for the computer to know what to do. (This is where the ROM comes in.) It tells the computer to look for the operating system and access the disk drive. The ROM holds the boot process which is the series of steps the computer follows when it is turned on. The only way to change the instructions on the ROM is to remove the chips from the main board and replace them.

CMOS Memory (complementary metal oxide semiconductor) **BATTERY POWERED MEMORY**

• CMOS stores important information about the configuration of the computer even when the power is off. During the boot process the computer checks for the amount of RAM and the available disk drives. The CMOS stores the boot data information such as the number of hard drive track and sectors. The computer needs to know this information to find the operating system of the computer during the boot up process.This memory is less permanent than ROM; it can be updated. When the system configuration is changed, the CMOS needs to be changed and updated also. In older systems this is done through a set up program. In Windows 95, the plug and play feature helps with updating when new devices are added. The CMOS needs little power to keep its data. It is powered by a battery.

Types of memory that can be added to a computer:

1. DRAM (Dynamic Randon Access Memory) is the memory used for the main memory.
2. SRAM (Static Random Access Memory) is also known as cache memory, it speeds up the processing of the CPU and works at very high speeds. It is also the most expensive type of memory.
3. VRAM (Video Random Access Memory) used by the video adapter to send data images to the monitor, it is commonly used for complex graphic applications, or photo refinishing. For everyday word processing or basic computing that does not require complex graphics DRAM memory can be substituted.

[Home] [Computer Store] [FAQ] [History]
[Hardware] [Operating Systems] [Software] [Adaptive Technology]

---

Mail comments to Josh and Patrick