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"Memory" is a term that tends to confuse new and non-tech oriented computer users. I don't know how many times I've suggested that flaky behavior by such a person's computer might be attributable to a shortage of memory, only to have them somewhat quizzically inform me that there is still plenty of empty space on their hard drive.

Well , yes , hard drive storage space is a sort of memory, and perhaps a kind that non-techies find easier to cognate than the more abstract concept of dynamic memory. There is also ROM, or Read Only Memory, stored in a chip on the computer's motherboard. However, when tech literate people refer to computer "memory," they are talking about RAM, or Random Access Memory, a computer's capacity of which is determined by the number and capacity of its RAM modules, whose silicon chips can store information dynamically so long as they remain powered up. RAM memory disappears when the computer is shut down.

Your computer and software applications is essentially operate on RAM. When you start the computer, it loads information stored magnetically in the operating system files on your hard drive into RAM, these days using up a large chunk of it, usually 30 MB or more. Then when you start up applications, their information is also loaded into RAM, using up more of your reserves. The number of programs you can have open at one time is limited by the amount of RAM capacity that has been installed on your computer (actually, there are ways of temporarily tapping unused storage space on your hard drive to artificially increase RAM capacity, but I'll not get into that in this tutorial).

You can get a snapshot of how much memory the System and each program you have open are using by selecting "About This Computer" From the Apple Menu when the Mac OS Finder is your active (frontmost) application. In the window that opens, you will see a bar graph, with a bar for the System and each open application. The respective length of each bar indicates the amount of RAM that has been assigned to that application, and the shaded in portion of the bar tells you how much of that allocation the program is actually using at the time. Note, however, that some programs use little of their allocation when no documents or files are open, so check a program's memory usage when it is displaying a typical document.

If you notice that one or more of the bars pertaining to applications (not the System) are almost fully shaded in, that means that the program is testing the limits of its assigned memory allocation, and it probably needs to be assigned more memory to work with. On the other hand, if an application is using only two-thirds or less of its memory allotment, you can probably reduce its memory allocation if you find yourself running short of RAM capacity to run the number of programs you want.

In order to adjust the program's memory allocation, first quit the program, and find the application file's icon , which will usually be located inside a folder with the name of the application along with a number of other files. An alias of the program icon will not work.

Single click on the icon to highlight it, and then select "Get info" from the File menu or just use the Command + I keyboard shortcut. An information box will open, and in it you will see a pull-down submenu beside the word "Show:". Use the menu to select "Memory," and a dialog will appear under the heading "Memory Requirements," in which there will be three entries: "Suggested size;" "Minimum size;" and "Preferred size."

Suggested size is what the developer recommends for general, all round use, while Minimum size is the smallest allocation you can set without degrading program performance (and it may be a bit cranky even at that setting). Preferred size is the actual amount of memory assigned to the program, and you can change it by dragging over the number to highlight it, hitting Delete, and then typing in a new number. Note that the application cannot be running when you are changing memory settings, although you can check Get Info without shutting down the program. You also cannot adjust memory when your Mac is running under the Simple Finder mode.

Note also that if you have Virtual Memory (that hard drive memory borrowing fudge I mentioned above) turned on, nominal memory requirements will be substantially less.

Indications that a program may be starving for an increased memory allocation include if you frequently get out-of-memory messages, if a program slows down a lot while you are using it, or if it just seems to crash a lot, especially if you get a dialogue indicating a Type 1 error.

If you notice any of these phenomena happening, it's well worth experimentally increasing the affected program's memory allocation. Web browsers and graphics programs can be especially susceptible to being overdrawn at the memory bank because their memory requirements can increase substantially under normal operations. If you have lots of unused RAM capacity, then giving such programs up to 50 percent more than the suggested size can be helpful. If RAM is a bit tighter, then increase memory allocations by 10% increments until the out of memory problems disappear.

If increasing aid programs memory allocation does not eliminate the problem, then it may be something else, but that's another movie.