Why study programming languages?

1. Why study programming languages? • Increased capacity to express ideas • Constructs we can express can be constrained by the language we know • Improved background for choosing appropriate language • Should choose language appropriate for task not just the one that we know • Increased ability to learn new languages • Learning new languages and learning language fundamentals enables us to learn other languages more easily • Better understanding of the significance of implementation • Aids in finding bugs • Enables us to write more efficient code • Overall advancement of computing • Educated people will make better language choices Section 1.1

2. Computer Applications & Languages • Scientific • Number crunching, weather forecasting, codebreaking, plane/missile trajectories • Language requirements: • Real numbers • Large amount of calculations (hence efficient) • Arrays, matrices • Selection, Counting loops • Languages: • Assembly, Fortran, Algol Section 1.2

3. Computer Applications & Languages • Scientific Applications • Language requirements: reals, efficiency, arrays, loops • Languages: Fortran, assembly, Algol • Business • Financial transactions • Language requirements: • Report production • Exact (but low) precision (e.g., money) • Character data • Languages: COBOL, RPG Section 1.2

4. Computer Applications & Languages • Scientific Applications: reals, efficiency, arrays, loops Fortran, assembly, Algol • Business Applications: reports, decimal precision, characters COBOL, RPG • Artificial Intelligence • Deductive systems, reasoning, machine learning • Language requirements: • Symbolic computation (“names” not numbers) • Lists of data (not arrays) • Recursion • Languages: LISP, Scheme, Prolog Section 1.2

5. Computer Applications & Languages • Scientific Applications: reals, efficiency, arrays, loops Fortran, assembly, Algol • Business Applications: reports, decimal precision, characters COBOL, RPG • AI Applications: Symbolic computation, Lists of data, Recursion LISP, Scheme, Prolog • Systems Programming • Operating systems, compilers, debuggers, etc. • Language requirements: • FAST execution • External device interfaces • Languages: C, Assembly Section 1.2

6. Computer Applications & Languages • Scientific Applications: reals, efficiency, arrays, loops Fortran, assembly, Algol • Business Applications: reports, decimal precision, characters COBOL, RPG • AI Applications: Symbolic computation, Lists of data, Recursion LISP, Scheme, Prolog • Systems Programming: fast, external devices C, Assembly • Scripting Languages • Typically not general-purpose, originally utility in nature • Language requirements: vary since they are more specific • Languages: csh, tcl, perl, javascript, php Section 1.2

7. Computer Applications & Languages • Scientific Applications: reals, efficiency, arrays, loops Fortran, assembly, Algol • Business Applications: reports, decimal precision, characters COBOL • AI Applications: Symbolic computation, Lists of data, Recursion LISP, Scheme, Prolog • Systems Programming: fast, external devices C, Assembly • Scripting Languages: specific not general csh, tcl, perl, javascript, php • Special-purpose languages • Domain-specific, typically small • Language requirements: Vary with domain • Languages: HTML, GPSS, Excel Section 1.2

8. Language Characteristics • Simplicity/Orthogonality • Control structures • Data types and structures • Syntax design • Abstraction • Expressivity • Type checking • Exception handling • Restricted aliasing Section 1.1

9. Selected Language Characteristics • Simplicity • { … } vs. begin … end vs. if … endif • foo++ vs. foo += 1 vs. foo = foo + 1 • Syntax design • { … } vs. begin … end vs. if … endif • affects readability and writability • Exception handling • Affects reliability (impacts syntax, …) Section 1.1

10. Language Influences • Architecture • von Neumann • Memory • CPU • ALU • Programming Maturity (Methodologies) • Unstructured • Procedure-oriented (top-down, functions, …) • Data-oriented (ADT, OO) Section 1.1

11. Language Categories (most important ones) • Imperative • Functional • Logic • Object oriented • Is it an imperative sub-group? Section 1.5

12. Imperative Programming Languages • Central features are variables and assignment statements • Design based on the von Neumann architecture • Variables model memory cells • Assignment statement models the “piping operation” – operands piped from memory to CPU; result piped from CPU to memory Section 1.5

13. Functional Programming Languages • Main features are functions and function calls (recursion instead of iteration) • Design is based upon mathematical functions Section 1.5

14. Logic programming languages • Also called rule-based languages and declarative languages • Programmer gives rules that specify what a solution looks like and not how desired solution is achieved Section 1.5

15. Object Oriented Programming Languages • Provides a feature for building objects • Provides a method for specifying inheritance • Provides polymorphism • Same name for different functions (method overriding) • Dynamic binding of function call to function body Section 1.5

16. Implementation methods • Compilation • Interpretation • Hybrid Section 1.7

17. Compilation • Compiler translates program into machine language that is executed on the computer • Execution is fast Section 1.7

18. source machine code Compilation Lexical analyzer Linker Syntax analyzer executable Semantic analyzer/ Intermediate code generation Optimizer Code generator machine code Section 1.7

19. Interpreter • Pure interpretation means there is no translation of the source program • Program called an interpreter is executed by the computer • Interpreter fetches/decodes/executes source program • Slower and requires more space than the compilation process Section 1.7

20. Hybrid • Source program is translated into an intermediate code that is then interpreted • Examples • Java is translated into byte code that can be interpreted • Perl is compiled before execution in order to detect compilation errors (unlike shell languages) Section 1.7