Why Functions?

• Flexibility and Reuse of code (with different arguments)
• Team Work (many ``units'' or ``parts'' to be developed)
  • Can be done in parallel
  • Different teams
  • Interface must be clearly defined!

What is a function?

• Black box view
• Takes ``inputs''
• Returns a single ``output'' (of some type)
• Can do any ``complicated'' calculations etc. (all Fortran constructs).