There are three basic types of button; command buttons, radio buttons and check buttons. Buttons are used by moving the mouse pointer over the button (it will then be highlighted, as is "Choice 3" below) and pressing the left mouse button. The illustration below demonstrates each of the three types.
The buttons labelled "Command 1", "Command 2" and "Command 3" are command buttons. These perform a particular action, which is usually determined by the text within the button. Typically command buttons have a slightly raised look. A typical example is the "Clear" button visible on the main gap4 window. See the illustration in section The Output and Error Windows.
The buttons underneath, labelled "Choice 1", "Choice 2" and "Choice 3" are radio buttons. These have small diamonds to the left of each name. Only one of these boxes in each group of radio buttons (it is possible to have several distinct groups) may be set at any one time. In this example "Choice 1" has been selected. For example, selecting "Choice 3" will now clear the diamond next to "Choice 1" and fill the diamond next to "Choice 3".
The bottom row of buttons are check buttons. These each have small boxes to the left of each name. They act similarly to radio buttons except that more than one can be selected at any one time. Here we have "Check 2" and "Check 3" selected, with "Check 1" deselected. Pressing a check button will toggle it; so clicking the left mouse button on "Check 2" would deselect it and clear the neighbouring box. The "Scroll on output" button is an example of a check button. See the illustration in section The Output and Error Windows.