Difference between constants and read-only variables.

While constants and read-only variable share many similarities, there are some important differences:

• Constants are evaluated at compile time, while the read-only variables are evaluated at run time.
• Constants support only value-type variables, while read-only variables can hold reference-type variables.
• Constants should be used when the value is not changing during run time, and read-only variables are used mostly when their actual value is unknown before run time.
• Read-only variables can only be initialised at the time of declaration or in a constructor.