Slide 1

Programming Languages Structure

• Introduction

Slide 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).

Slide 3

Course Assessment

• Mid-term Exam 30%

• Project 30%

• Final exam 40%

Slide 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

Slide 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

Slide 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)

Slide 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

Slide 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

Slide 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

Slide 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

Slide 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.

Slide 12

Language Evaluation Criteria

• Readability

• Writability

• Reliability

• Cost

Slide 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)

Slide 14

Writability

• Simplicity/Orthogonality

• Support for abstraction (process abstraction and data abstraction)

• Expressivity (convenient ways of specifying computation)

Slide 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).

Slide 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)

Slide 17

Implementation Methods 1. Compilation

Source Program

Machine Language

MachineFetch-Execute

• Source programs are translated to machine language

Slide 18

Implementation Methods 1. Compilation

Source Program

Lexical Analyzer

Syntax Analyzer

Intermediate CodeGenerator

Code Generator

Symbol Table

Lexical units

Parse trees

Optimization

Intermediate code

Machine code

Slide 19

Implementation Methods 2. Pure Interpretation

Source Program

Interpreter

Machine

Fetch-Execute

Virtual Machine

• Source programs are directly interpreted by another program without any translation.

Slide 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)

Slide 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++