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Figure 4-52 Not enough RAM to load program D

Windows’ virtual memory starts by creating a page file that resides somewhere on your hard drive. The page file works like a temporary storage box. Windows removes running programs temporarily from RAM into the page file so other programs can load and run. If you have enough RAM to run all your programs, Windows does not need to use the page file; Windows brings the page file into play only when insufficient RAM is available to run all open programs.

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NOTE Virtual memory is a fully automated process and does not require any user intervention. Tech intervention is another story!

To load, Program D needs a certain amount of free RAM. Clearly, this requires that unloading some other program (or programs) from RAM without actually closing any programs. Windows looks at all running programs—in this case A, B, and C—and decides which program is the least used. That program is then cut out of or swapped from RAM and copied into the page file. In this case, Windows has chosen Program B (Figure 4-53). Unloading Program B from RAM provides enough RAM to load Program D (Figure 4-54).

It is important to understand that none of this activity is visible on the screen. Program B’s window is still visible, along with those of all the other running programs. Nothing tells the user that Program B is no longer in RAM (Figure 4-55).

Figure 4-53 Program B being unloaded from memory

Figure 4-54 Program B stored in the page file—room is made for Program D

Figure 4-55 You can’t tell whether a program is swapped or not.

So what happens if you click on Program B’s window to bring it to the front? The program can’t actually run from the page file; it must be loaded back into RAM. First, Windows decides which program must be removed from RAM, and this time Windows chooses Program C (Figure 4-56). Then it loads Program B into RAM (Figure 4-57).

Figure 4-56 Program C is swapped to the page file.

Figure 4-57 Program B is swapped back into RAM.

Swapping programs to and from the page file and RAM takes time. Although no visual clues suggest that a swap is taking place, the machine slows down quite noticeably as Windows performs the swaps. The alternative (Figure 4-58) is far less acceptable. Page files are a crucial aspect of Windows operation.

Figure 4-58 The alternative to page files

Windows handles page files automatically, but occasionally you’ll run into problems and need to change the size of the page file or delete it and let Windows re-create it automatically. The page file is PAGEFILE.SYS. You can often find it in the root directory of the C: drive, but again, that can be changed. Wherever it is, the page file is a hidden system file, which means in practice that you’ll have to play with your folder-viewing options to see it.

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NOTE If you have a second hard drive installed in your PC, you can often get a nice performance boost by moving your page file from the C: drive (the default) to the second drive. To move your page file in all versions of Windows, go to the Control Panel | System applet and select the Advanced tab in 2000/XP or Advanced system settings menu in Vista/7. This opens the System Properties dialog box. In the Performance section, click the Settings button to open the Performance Options dialog box. Select the Advanced tab, and then click the Change button in the Virtual Memory section. Select a drive from the list and give it a size or range, and you’re ready to go.

Just don’t turn virtual memory off completely. Although Windows can run without virtual memory, you will definitely take a performance hit.

Tech Utilities

Windows offers a huge number of utilities that enable techs to configure the OS, optimize and tweak settings, install hardware, and more. The trick is to know where to go to find them. This section shows the six most common locations in Windows where you can access utilities: right-click, Control Panel, System Tools, command line, Administrative Tools,