Language Evaluation Criteria
• Readability: the ease with which programs can be read and understood
• Writability: the ease with which a language can be used to create programs
• Reliability: conformance to specifications (i.e., performs to its specifications)
• Cost: the ultimate total cost
Evaluation Criteria: Readability
• Overall simplicity
– A manageable set of features and constructs
– Few feature multiplicity (means of doing the same operation)
– Minimal operator overloading
• Orthogonality
– A relatively small set of primitive constructs can be combined in a relatively small number of ways
– Every possible combination is legal
• Control statements
– The presence of well-known control structures (e.g., while statement)
• Data types and structures
– The presence of adequate facilities for defining data structures
• Syntax considerations
– Identifier forms: flexible composition
– Special words and methods of forming compound statements
– Form and meaning: self-descriptive constructs, meaningful keywords
Evaluation Criteria: Writability
• Simplicity and orthogonality
– Few constructs, a small number of primitives, a small set of rules for combining them
• Support for abstraction
– The ability to define and use complex structures or operations in ways that allow details to be ignored
• Expressivity
– A set of relatively convenient ways of specifying operations
– Example: the inclusion of for statement in many modern languages
Evaluation Criteria: Reliability
• Type checking
– Testing for type errors
• Exception handling
– Intercept run-time errors and take corrective measures
• Aliasing
– Presence of two or more distinct referencing methods for the same memory location
• Readability and writability
– A language that does not support ―natural‖ ways of expressing an algorithm will necessarily use ―unnatural‖ approaches, and hence reduced reliability
Evaluation Criteria: Cost
• Training programmers to use language
• Writing programs (closeness to particular applications)
• Compiling programs
• Executing programs
• Language implementation system: availability of free compilers
• Reliability: poor reliability leads to high costs
• Maintaining programs
Evaluation Criteria: Others
• Portability
– The ease with which programs can be moved from one implementation to another
• Generality
– The applicability to a wide range of applications
• Well-definedness
– The completeness and precision of the language‘s official definition.