It may be months or even years before the combination of events occurs that makes the error appear. It is at this time that the simple explanation of the program through a flowchart is useful. At other times the program may have to be altered because conditions have changed. A simple explanation of where the changed conditions affect the program is very important. Remember that the flowchart should be developed before attempting to write any computer language representation of the program.
Many students try to develop the flowchart from a program that they have slaved over.
You will find it much quicker to do the flowchart first, and the program later. Start the program. Read number 1 from the keyboard. Read number 2 from the keyboard. Add number 1 and number 2.