SMALLTALK is a new programming language developed at the Xerox Palo Alto Research Center for use on the experimental personal computer. It is made up of “activities,” computerlike entities that can perform a specific set of tasks and can also communicate with other activities in the system. New activities are created by enriching existing families of activities with additional “traits,” or abilities, which are defined in terms of a method to be carried out. The description of the family “box” shown here is a dictionary of its traits. To create a new member of the family box, a message is sent to the trait “new” stating the characteristics of the new box in terms of specific values for the general traits “location,” “angle” and “size.” In this example “new” has been filled in to specify a box located in the center of the screen with an angle of zero degrees and a side 100 screen dots long. To “show” the new box, a member of the curve-drawing family “brush” is given directions by the open trait “shape.” First the brush travels to the specified location, turns in the proper direction and appears on the screen. Then it draws a square by traveling the distance given by “size,” turning 90 degrees and repeating these actions three more times. The last trait on the list is open, indicating that a numerical value is to be supplied by the user when the trait is invoked by a message. A box is “grown” by first erasing it, increasing (or decreasing) its size by the value supplied in the message and redisplaying it.