Programming Languages Design Considerations (Qualities) Readability –Simplicity and Clarity –Orthogonality –Control Statements –Data Types and Structures –Syntax considerations Writability –Simplicity and Orthogonality –Abstraction –Expressivity

Programming Languages Design Considerations (Qualities) Reliability –Type Checking –Exception Handling –Aliasing –Readability & Writability

Programming Languages Design Considerations (Qualities) Cost –training –writing –compiling –executing –implementing –reliability –maintaining

Programming Languages Design Considerations (Qualities) Binding –Language definition time –Language implementation time –Program writing time –Program compile –Program load time –Program run time

Practical Considerations Architecture Contextual constraints Virtual machines and interpreters Standards Legacy Systems

Architecture Languages designed to match architecture –Von Neumann –Exception: Lisp machines –RISC

Contextual Constraints architecture application area operating system network programming community preferences –general purpose vs special purpose –compiled vs interpreted

Virtual Machines & Interpreters compiler written for virtual machine –written only once interpreters for real machines allows experimentation –eliminates machine specific details

Standards ANSI Cobol (1985) ISO Fortran (1997) ISO Prolog (1995) ANSI/ISO C (1999) ANSI Basic (1989) ANSI/ISO Ada (1995) ANSI Smalltalk (1998) ISO Pascal (1990)

Legacy Systems 90% programmer’s time maintaining backward compatibility necessary ponderous committee vs individual design

Assignment Be able to answer the review questions on pages 33 & 34, particularly –3,4,5,6,7,8,9,12,13,14,18,20,23,24,25,26,27,32