How to Design a Computer Program

When programming professionals write a new program, they are usually handed a list of specifications. These specs detail what data they will be passed, how the data should be processed and what output the user wants to see. The specs determine the overall design of the program, so the better the specs, the better the finished program.

Instructions

1. Define the data that needs to be processed. The programmer will need to know what type of data it is (numbers or letters) and the length of each data field. An employee record might look like this:
   Last Name Char 25
   First Name Char 25
   Middle Init Char 1
   Date of Birth Date mm/dd/yyyy
   Marital status Char 1 (M, D, S)

2. Create a handwritten sample of the report or file you expect to see as the output from the program. Designing the output early helps determine if you have all the data you need and defines what data needs to be calculated.

3. 

   Draw a logic flow diagram. This should show the steps the programmer will need to take to get from raw data input to finished output. Use terms like "calculate gross pay" and let the programmer write the code to do that step.

4. Show all calculations that are necessary to reach your final goal. There are many ways to calculate values. While they might seem straightforward, don't leave these items to the programmer's interpretation. For example,if you need to calculate income taxes after 401(k) funds have been removed, show the steps like this:
   Net pay = Gross pay - pre-tax deductions - 401(k) deductions.

5. Give the programmer measurable goals, including a timetable. Break the program down by tasks and assign a date for each task to be complete. For example:
   Initial review - 1 week
   Input screens - 2 weeks
   Output files and reports - 2 weeks
   Final review - 1 week
   This clearly tells the programmer you expect the task to be completed in 6 weeks' time.

Tips & Warnings

• No design is complete without a timetable. If you need the program created within 2 weeks, make sure it is stated in the specs. Your programmer needs this to know if the project can be completed successfully.

• Incomplete specs will lead to time delays and cost overruns, so be detailed and specific when writing your specs.