KC 8.2.1 – Product measurements - Size

Lines of code (LOC) & Function/feature points are the most commonly used size measures for software.

Lines of code

• A size-oriented metric
  
• Easy to measure
  
• Easy to compare
  
• Easy to differentiate wrt time, cost, etc.
  
• Programming language dependent (e.g. 1 OO-LOC = 3 3GL-LOC = 9 assembler-LOC)
  
• Meaningless in isolation
  
• Penalize efficient design and coding
  
• "Measure what is easy to measure, not what is important to measure"

Function/feature points

• An empirical formula based on...
  
• ...the number of inputs to a (sub-)system
  
• ...the number of outputs it produces
  
• ...the number of files (data repositories) used
  
• ...the number of interfaces to other systems
  
• ...the number of algorithms encapsulated
  
• Numerical measure the "functionality" or "utility" of a system.
  
• But is empirically derived and does not correspond to any directly perceivable quantity (i.e. just a number)