Trackbars are useful when you want the user to select a discrete value or a set of consecutive values in a range. For example, you might use a trackbar to allow the user to set the repeat rate of the keyboard by moving the slider to a given tick mark.
The slider in a trackbar moves in increments that you specify when you create it. For example, if you specify that the trackbar should have a range of five, the slider can only occupy six positions: a position at the left side of the trackbar and one position for each increment in the range. Typically, each of these positions is identified by a tick mark.
You create a trackbar by using the CreateWindowEx function, specifying the TRACKBAR_CLASS window class. Once you have created a trackbar, you can use trackbar messages to change many of its properties. Changes that you can make include setting the minimum and maximum positions for the slider, drawing tick marks, setting a selection range, and repositioning the slider.