The empty string is written as . The DO statement simplifies the coding of iterative procedures. The DO statement causes the statements which follow, up to and in- cluding the statement numbered n, to be executed repeatedly. This group of statements is called the range of the DO statement. The index is in- cremented and tested before the range of the DO is executed.
Implementation becomes standard of correctness.
Definition should describe how the language behaves as ab- stractly as possible. Each has different purposes and strengths. Operational Semantics Define behavior of language on an abstract ma- chine. Explicate the meaning of a language feature by proving that it has the same behavior as a combina- tion of simpler features. We can prove this without referring to the individual assignment and addition operations.