To take a screenshot on a desktop, the method depends on your operating system and keyboard: For Windows desktops:

• To capture the entire screen and save it as a file, press the Windows logo key + Print Screen (PrtScn) key simultaneously. The screen may dim briefly, and the screenshot will be saved in the Pictures > Screenshots folder.
• To capture the entire screen to the clipboard without saving automatically, press the Print Screen key alone. You can then paste (Ctrl + V) the image into an image editor or document.
• To capture the currently active window only, press Alt + Print Screen. This copies the active window screenshot to the clipboard for pasting.
• Alternatively, you can use the Snipping Tool by pressing Windows logo key + Shift + S to select part of the screen for capture.

For Mac desktops:

• Press Shift + Command + 3 to capture the entire screen and save the screenshot to the desktop.
• Press Shift + Command + 4 to capture a selected portion of the screen by dragging a selection area.
• Press Shift + Command + 4, then Space bar, to capture a specific window.

These keyboard shortcuts provide quick and effective ways to print screen on desktop computers using Windows or macOS systems.