To get an idea of how much things have changed over the last decade, an excerpt from Inside the IBM PC, written by Peter Norton in 1983, describes the merits of IBM's new XT computer:
However, for those who want to know more, this reference guide provides a general overview of what memory is and how it works.
A good example of this is when the CPU loads an application program -- such as a word processor or page layout program -- into memory, thereby allowing the application program to run as quickly as possible. In practical terms, this means you can get more work done with less time spent waiting for the computer to perform tasks.
When you enter a command from the keyboard, it calls for data to
be copied from a storage device (such as a hard disk drive or
CD-ROM drive) into memory, which can provide data to the CPU more
quickly than storage devices.
This "putting things the CPU needs in a place where it can get at them more
quickly" process is similar to placing various electronic files and documents
you're using on the computer into a single file folder or directory. By doing
so, you keep them handy and avoid searching in several places every time you
need those documents.
To clarify this common mix-up, it helps to compare your computer to an office that contains a work table and a set of file cabinets.
The work table represents memory, which offers quick and
easy access to the files you're working on at the moment.
The file cabinets represent the computer's hard disk, which
provides high-capacity storage.
Another important difference between memory and storage is that the information stored on a hard disk remains intact even when the computer is turned off. However, any data held in memory is cleared when the computer is turned off. (It's like saying that any files left on the work table at closing time will be thrown away.)
It's important to save frequently while working on a computer. The computer memory holds any changes you make to a document until you save the changes to a disk. If anything interrupts the computer's operation -- such as a power outage or system error -- any changes made, but not saved, are lost.
Perhaps you already know what it's like to work on a system that doesn't have quite enough memory. Things run a little more slowly at times, memory errors can occur more frequently, and sometimes you can't launch an application or a file without first closing or quitting another. On a system with sufficient memory, however, you can do multiple tasks at once -- such as printing one document while working on another -- and you can keep multiple applications open simultaneously.
Type of User/Usage Recommended RAM
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Light Administrative
Light word-processing, light e-mail 8MB - 12MB
Medium Administrative
Word-processing, E-mail, Fax & Comm. Software, Database.
1-2 applications open at a time. 12MB - 16MB
Heavy Administrative
Word-processing, E-mail, Fax & Comm. Software, Spreadsheet,
Business graphics. > 3 applications open at a time. 16MB - 24MB
Light Customer Service
E-mail, Database. 1-2 applications open at a time. 8MB - 12MB
Heavy Customer Service
E-mail, Database, Fax & Comm. Software, Word processing.
> 3 applications open at a time. 12MB - 20MB
Light Number Crunching
Spreadsheet, E-mail, Accounting software
1-2 applications open at a time. 16MB - 24MB
Heavy Number Crunching
Spreadsheets, Statistical applications, Research, large
databases. > 3 applications open at a time. 24MB - 32MB
Light Graphics
Word-processing, Page layout software, Illustration/graphics
software. 1-2 applications open at a time. 32MB - 64MB
Heavy Graphics
Word-processing, Page layout software, Illustration/graphics
software, Photo editing, Presentation software, Font packages,
multimedia. > 3 applications open at a time. 64MB - 128MB
Executive/ Management
Word-processing, E-mail, Fax & Comm. Software, Spreadsheets,
Business graphics programs, Database, Presentation software.
> 3 applications open at a time. 16MB - 32MB
Light - Medium Design
CAD software, CAM software 32MB - 128MB
Heavy Design
3D CAD software, CAM software solid modeling 256MB - 2GB
Note:
Naturally, a chart such as this evolves as memory needs and trends change.
While we can speculate today about the `right' amount of memory given systems
or tasks, one thing appears certain: over time, developers of software and
operating systems will continue to add features and functionality to their
products. This will continue to drive the demand for more memory.
A common memory product is the Single In-line Memory Module, or SIMM. As you can see from the illustration, a typical SIMM consists of a number of DRAM chips on a small Printed Circuit Board, or PCB, which fits into a SIMM socket on a computer's system board (more on this later).
SIMMs come in a variety of forms, including 30- and 72-pin formats. These and other types of memory products are covered in greater detail in the `Bits and Bytes' section coming up later...
