Runtime and Compile-time constants in C++
These are the constants whose respective values can only be known or computed at the time of running of source code. Run time Constants are a bit slower than compile-time constants but are more flexible than compile-time constants. However, once it is initialized, the value of these constants can’t be changed.
Below is the program for illustration of Runtime constants:
These are the constants whose respective value is known or computed at the time of compilation of source code. Compile-time constants are faster than run-time constants but are less flexible than run-time constants.
Below is the program for illustration of Compile-time Constant:
Difference between Run-time and Compile-time constants
|Compile-time constants||Run-time constants|
|1.||A compile-time constant is a value that is computed at the compilation-time.||Whereas, A runtime constant is a value that is computed only at the time when the program is running.|
|2.||A compile-time constant will have the same value each time when the source code is run.||
A runtime constant can have a different value each time the source code is run.
It is generally used while declaring an array size.
It is not preferred for declaring an array size.
|4||If you use const int size = 5 for defining a case expression it would run smoothly and won’t produce any compile-time error.||Here, if you use run-time constant in your source code for defining case expression then it will yield a compile-time error.|
|5||It does not produces any compile time error when used for initializing an enumerator.||
Same compilation error, if runtime constant is used for initializing an enumerator.