There are several input constraints for this tiny tool.  As stated above, there are four input categories: Activity, Successors, Predecessors, and Duration.  Each input category has one or more constraints associated with it.

Activity:

Ø      There can be up to 10 activities (tasks) entered for the project.

Ø      All activity names must be a single letter or digit.

Ø      The first activity entered (Start) must be named S.

Ø      The last activity entered (Finish) must be named Z.

Successors:

Ø      Each activity can have any number of successors.

Ø      The successors must be activity names that appear in the table entries below that activity.

Predecessors:

Ø      Each activity can have any number of predecessors.

Ø      The predecessors must be activity names that appear in the table entries above that activity.

Duration:

Ø      The duration for all activities must be a non-negative integer.

Ø      The start and finish activities’ durations must be 0.