Software should be easily understood by another programmer.
When we write code, we should be using meaningful identifiers, indentation, and internal commentary.
This allows software to be easily updated or maintained at a later date.
This is very important as we may not be working on the same code for a long period of time.
It may be another programmer who has never seen our code before.
If code is not readable, clear, and formatted properly this would likely not be maintainable code.
