1. Programming Languages Structure
Introduction

2. Text/References
Robert W. Sebesta, “Concepts of Programming Languages”, Fourth Edition Addison-Wesley (1999).
T.W. Pratt and M.V. Zelkowitz, “Programming Languages – Design and Implementation” Fourth Edition, Prentice-Hall (2001).
Ravi Sethi, “Programming Languages - Concepts and Constructs” Second Edition, Addison-Wesley (1996).

3. Course Assessment
Mid-term Exam 30%
Project %
Final exam %

4. Why study Programming Language Concepts?
Increased capacity to express ideas
Improved background for choosing appropriate languages
Increased ability to learn new languages
Better understanding of the implementation of concepts
Increased ability to design new languages

5. Program - Definitions
A program is a description of a set of actions that we want a computer to carry out.
A program is a model of some process in the real or mathematical world.
A program is a sequence of instructions for a machine to perform a specific task.
A notational system for describing computation in machine-readable and human-readable form

6. Programming Domains
Scientific: Heavily based on numerical algorithms (Fortran, C)
Business Applications: Storage, retrieval, and formatting of data, reporting. (COBOL)
Artificial Intelligence: Symbolic computing, List directed processing (LISP, Prolog)
Systems Programming: Fast, Low level features (C)
Internet: Web based programming (Perl, Java)
Simulation: Process modeling (MATLAB, GPSS)

7. Programming Paradigms: 1. Imperative
Statement oriented languages
Every statement changes the machine state
Computation is expressed by a sequence of actions.
Heavily based on von Neumann architecture
Provides variables, assignments, and iterative repetitions.
Examples: Fortran, C

8. Programming Paradigms: 2. Declarative
Problem specification using relations or functions.
Functional programming (applying functions to given parameters).
Logic programming (deductive reasoning, rule based)
Examples: LISP, ML, Haskell, Prolog

9. Programming Paradigms: 3. Concurrent
Parallel execution of processes.
Multi-tasking or multi-threading primitives.
Inter process communication and synchronization.
Helps in speeding up the execution of parallel algorithms
Examples: Concurrent C, Java, Fortran-90

10. Programming Paradigms: 4. Object Oriented
Based on the concept of data abstraction.
Uses encapsulation (data hiding)
Supports inheritance (software reuse)
Suitable for programming in the large.
Examples: C++, Java, Smalltalk, Eiffel

11. Programming Paradigms: 5. Scripting
Contains a set of commands (scripts) to be executed.
Works in conjunction with a larger application, or are interpreted.
Examples: Perl, Javascript.

12. Language Evaluation Criteria
Readability
Writability
Reliability
Cost

13. Readability
Simplicity (Small number of basic components, less amount of feature multiplicity, restricted operator overloading).
Limited Orthogonality (Ways by which primitive constructs can be combined).
Control Structures (Structured programming)
Data types and structures (Arrays, records..)
Syntax design (Closeness to intended purpose)

14. Writability
Simplicity/Orthogonality
Support for abstraction (process abstraction and data abstraction)
Expressivity (convenient ways of specifying computation)

15. Reliability
Type checking (Compile-time checking of types of variables)
Exception handling (Ability to intercept errors, take corrective measures and continue).
Restricted aliasing (Multiple names associated with the same memory cell).

16. Cost
Cost of training
Cost of compiling (Compilation time)
Cost of execution (Optimization)
Cost of language implementation (Compiler, hardware etc).
Cost of maintenance (Repairs, changes and extensions)

17. Implementation Methods 1. Compilation
Source Program
Machine Language
Fetch-Execute
Machine
Source programs are translated to machine language

18. Implementation Methods 1. Compilation
Source Program
Lexical Analyzer
Lexical units
Syntax Analyzer
Parse trees
Intermediate Code
Generator
Symbol Table
Optimization
Intermediate code
Code Generator
Machine code

19. Implementation Methods 2. Pure Interpretation
Source Program
Fetch-Execute
Interpreter
Virtual Machine
Machine
Source programs are directly interpreted by another program
without any translation.

20. Implementation Methods 3. Hybrid Implementation
Compilation followed by interpretation.
Perl (Compiled to detect errors before interpretation)
Java (Compiled to platform independent byte codes, and interpreted by the JVM)

21. Programming Environments
Collection of tools used in the development of software.
Consists of a file system, a text editor, a linker, a compiler, a debugger, and development tools.
Helps increase productivity and quality.
Examples: Borland C++, Visual C++, Visual J++