PERT was developed in 1950 by the U.S. Navy during the Cold War and is intended for large projects, which are:

• Complex
• Require a series of sequential tasks
• Performed in parallel with other projects

PERT planning usually involves the following steps:

1. Identifying Tasks and Milestones: Every project involves a series of required tasks. These tasks are listed in a table allowing additional information on sequence and timing to be added later.
2. Placing the Tasks in a Proper Sequence: The tasks are analyzed and placed in a sequence to get the desired results.
3. Network Diagramming: A network diagram is drawn using the activity sequence data showing the sequence of serial and parallel activities.
4. Time Estimating: This is the time required to carry out each activity, in three parts:
   1. Optimistic timing: The shortest time to complete an activity
   2. Most likely timing: The completion time having the highest probability
   3. Pessimistic timing: The longest time to complete an activity
   
5. Critical Path Estimating: This determines the total time required to complete a project.

PERT not only determines the time to complete a specific software development activity, but also determines the cost.