Programming Languages: Concepts and History

Reasons for Studying Concepts of Programming Languages

• Studying programming languages enhances the capacity to express ideas by understanding how language features limit the expression of programming concepts.
• Awareness of programming language features reduces software development limitations.
• Studying programming language concepts builds appreciation for language features and encourages their use.
• Understanding many languages helps programmers choose appropriate languages for projects.
• Programming languages and related tools are always evolving, so familiarity with fundamental concepts makes learning easier.
• It allows for more intelligent use of a language.
• Enables understanding of choices in programming language constructs to become a better programmer.
• It helps with the overall advancement of computing.

Brief History of Programming Languages

• The first languages were machine languages from the earliest computers in the 1940s.
• Hundreds of programming languages and dialects exist.
• Most have a limited lifespan, but some have enjoyed success in specific domains and influenced future languages.
• Ada was named after Ada Lovelace, considered the first computer programmer in the 1800s.
• Algol, short for "Algorithmic Language," was designed by an international committee in 1959.
• C was designed in the 1970s to support the Unix operating system implementation.
• C++ was designed as a C extension in the 1980s to support object-oriented programming.
• Cobol was first designed in 1960, it stands for "Common Business Oriented Language" and uses English-like syntax.
• Fortran was designed by IBM in 1954 for scientific programming and stands for "Formula Translator."
• Lisp, short for "List Processor," was designed in 1960 for symbol manipulation and list processing in AI.
• Pascal is a high-level, general-purpose programming language developed in 1971.
• Machine Language emerged in the 1940s.
• Fortran and Cobol emerged in the late 1950s.
• Algol and PL/I emerged in the 1960s.
• Pascal and C emerged in the 1970s.
• C++ and Smalltalk emerged in the 1980s.
• Lisp and Scheme emerged in the 1960s and 1970s respectively.
• Prolog and CLP emerged in the 1970s and 1980s respectively.
• Eiffel and Java emerged in the 1990s.
• ML and Haskell emerged in the 1970s and 1990s respectively.

Introduction to Language Paradigms

• Programming languages facilitate communication on algorithms between people and computers.
• A programming paradigm represents algorithmic expressions for computing applications in specific domains.
• Imperative programming uses a series of steps for calculations, input, or output and uses procedural abstraction, assignments, loops, sequences, and conditional statements.
• Imperative programming languages include Cobol, Fortran, Pascal, C, and C++.
• Object-Oriented Programming uses interacting objects.
• Object modeling, classification, and inheritance are fundamental as the messages transform the object's state.
• Object-Oriented Programming languages include Smalltalk, Java, C++, and Eiffel.
• Functional programming uses mathematical functions each with an input and output.
• Functions combine with each other through functional composition, conditionals, and recursion.
• Functional programming languages include Lisp, Scheme, Haskell, and ML.
• Logic programming uses logical declarations, only dictating what should be accomplished.
• Execution of a logic program applies declarations to find solutions to a problem.
• Prolog is the major logic programming language.
• Event-driven programming relies on a continuous loop.
• It responds to events generated by user actions on the screen.
• Java and Visual Basic are major event-driven programming languages.
• Concurrent/Parallel programming is a set of cooperating processes.
• Processes share information frequently.
• Concurrent programming languages include SR and High-Performance Fortran.
• Some languages which support more than one paradigm are C++, Java and Leda.
• C++ is an imperative and object-oriented language.
• Java supports object-oriented and event-driven paradigms.
• Leda supports the imperative, object-oriented, functional and logic programming paradigms.

Application Domains/Programming Domains

• Application domains can be grouped into Science, Business, AI, Systems and Web.
• Scientific programming focuses on complex calculations and accuracy.
• It generally uses the imperative programming paradigm with arrays and matrices.
• Parallel programming languages are used for weather and ocean flow systems.
• Scientific programming languages include Fortran 90, C, and High-Performance Fortran.
• Business application systems include payroll, accounting, sales and marketing, and inventory.
• Cobol, RPG, and SQL have been used.
• The online ordering systems use event-driven languages such as Java and Tcl/Tk.
• AI focuses on modeling human intelligent behavior, and cognition.
• Functional and logic programming are common paradigms.
• Functional programming languages used are Lisp, Scheme, Haskell, and ML.
• Logic programming languages used are Prolog and CLP.
• System programmers design and maintain basic software.
• Operating systems, network software, compilers, debuggers, virtual machines, and interpreters fall under systems programming.
• Imperative, parallel, and event-driven paradigms are used.
• 95% of the Unix system is programmed in C.
• The World Wide Web is a dynamic area for e-commerce, government, industry, and academia.
• Object-oriented and event-driven paradigms are commonly used for web software.
• Web application languages include Perl, Tcl/Tk, JavaScript, PHP, and ASP.

Language Evaluation Criteria

• Language capabilities can be evaluated based on multiple criteria.
• Readability is how easily programs can be read and understood given their domain.
• Simplicity, orthogonality, control statements, data types, and syntax affect readability.
• Writability measures how a language can create programs for a problem domain.
• Factors influencing writability are simplicity, orthogonality, support for abstraction, and expressivity.
• Reliability means a program performs to its specifications under all conditions.
• Type checking, exception handling, aliasing, readability, and writability affect reliability.
• Cost includes training programmers, writing programs, compiling programs, and executing programs.
• Other factors in cost include the language implementation system and the cost of poor reliability.
• Costs from poor reliability can be very high, such as in nuclear power plants or X-ray machines for medical use.

Compilation Process

• The language a compiler translates is the source language.
• The compilation and program execution process consists of several phases.
• A lexical analyzer gathers source program characters into units like identifiers, special words, operators, and punctuation symbols.
• The lexical analyzer ignores comments.
• A syntax analyzer takes lexical units and constructs hierarchical parse trees which represent the syntactic structure.
• An intermediate code generator produces a program in a language between the source and machine language.
• Intermediate languages look like assembly languages by compiler and semantic analyzer.
• The semantic analyzer checks for syntax analysis errors, such as type errors.
• Optimization improves programs by making them smaller or faster, it is often optional.
• A code generator translates the optimized intermediate code program into an equivalent machine language program.
• A symbol table serves as a database of type and attribute information for user-defined names.
• The lexical and syntax analyzers write to the symbol table.
• The semantic analyzer and code generator read from the symbol table.
• Machine language generated by a compiler nearly always runs with other code.
• Most user programs and operating systems programs require input and output.
• Required system programs must be found and linked to the user program before a compiled program executes.
• Linking loads system programs to user programs.
• Linking is accomplished a system program called a linker.