In computing, a method of checking that a computer program is functioning correctly by causing the changing values of all the variables involved to be displayed while the program is running. In this way it becomes possible to narrow down the search for a bug, or error, in the program to the exact instruction that causes the variables to take unexpected values.

1. A clue that something has been present; SYN. vestige, shadow.
2. A just detectable amount; SYN. hint, suggestion.
3. Either of two lines that connect a horse's harness to a wagon or other vehicle or to a whiffletree.
4. el. A conducting path on a printed circuit board.

1. To follow, discover, or ascertain the course of development of something; SYN. follow.
2. To make a mark or lines on a surface; SYN. draw, line, outline, describe, delineate.
3. To go back over again, as of a route or steps: we retraced the route we took last summer.; SYN. retrace.

To execute a program in such a way that the sequence of statements being executed can be observed. See also debugger, single step.