for loop VS while loop in programming languages, c++/java?

Question

Which is better for performance? This may not be consistent with other programming languages, so if they are different, or if you can answer my question with your knowledge in a

Answer 1

On certain CPU architectures, the characteristics of the loop may provide opportunities for more optimization than the choice of for versus while.

In particular, FORTRAN and Pascal recommended a constant (rather than a variable) for the number of loop iterations which some CPUs can optimize. For example, on a Cyber (a 1970s Iron Dinosaur mainframe), a 15-bit register holds the for loop index which can easily be compared. A while instead uses one or two of the harder-to-access 60-bit registers. Also, a Cyber branch instruction is considerably more expensive than the loop housekeeping, or possibly the loop content. In such cases, a high level of optimization might unroll the loop to avoid all the overhead.

However, modern code generators don't work like they used to: source code is turned into an intermediate parse structure which abstracts such choices away. In short, for versus while makes no difference.