A Formal Design for Softare

The major idea of SP is to divide a programming task into easily understandable units. Within these units, it may be of little consequence whether the language used is COBOL, FORTRAN, PL/1, or any of the new SP languages. Language design (such as control structures) may determine the size of the program which is the largest easily understandable unit. This is at best a local optimization. I have seen well-structured programs written in assembly language, FORTRAN, and APL–none of which are known for their facilities to enhance structured programming. However, any language claiming to enhance SP should provide a facility for connection among program units: this could be as complex as the abstract type mechanisms of Liskov´s CLU or Wulf´s ALPHARD, or it could be a simple procedure/macro facility. Poor design of these features limits the effectiveness of languages like FORTRAN and COBOL in the construction of well-structured programs. These facilities are often faked by a preprocessor or by system convention.