What is a programming language?

What is a programming language?  

Why are there so many programming languages?

What are the types of programming languages?

Does the world need new languages?

programming language 

 A programming language is a set of rules that provides a way of telling a computer what operations to perform. 

 A programming language is a set of rules for communicating an algorithm. It provides a linguistic framework for describing computations

Introduction A programming language is a notational system for describing computation in a machine-readable and human-readable form. A programming language is a tool for developing executable models for a class of problem domains.

English is a natural language. It has words, symbols and grammatical rules. 

 A programming language also has words, symbols and rules of grammar.  The grammatical rules are called syntax. Each programming language has a different set of syntax rules.

Why are there so many programming languages?

 Programming languages have evolved over time as better ways have been developed to design them. ◦ First programming languages were developed in the 1950s ◦ Since then thousands of languages have been developed. Different programming languages are designed for different types of programs. 

What are the types of Programming Languages

  1. First Generation Languages 
  2.  Second Generation Languages 
  3.  Third Generation Languages 
  4. Fourth Generation Languages 
  5. Fifth Generation Languages
  • First Generation Languages    Machine language    
Operation code – such as addition or subtraction. ◦ Operands – that identify the data to be processed.  Machine language is machine dependent as it is the only language the computer can understand. Very efficient code but very difficult to write.
  • Second Generation Languages Assembly languages 
Symbolic operation codes replaced binary operation codes. Assembly language programs needed to be “assembled” for execution by the computer. Each assembly language instruction is translated into one machine language instruction. ◦ Very efficient code and easier to write.
  • Third Generation Languages
Closer to English but included simple mathematical notation. Programs written in source code which must be translated into machine language programs called object code. 
 The translation of source code to object code is accomplished by a machine language system program called a compiler.  Alternative to compilation is interpretation which is accomplished by a system program called an interpreter. 
 Common third generation languages 
◦ FORTRAN 
◦ COBOL 
◦ C and C++ ◦ Visual Basic
  • Fourth Generations Languages
 A high level language (4GL) that requires fewer instructions to accomplish a task than a third generation language. 
Used with databases
 ◦ Query languages
 ◦ Report generators 
◦ Forms designers 
◦ Application generators
  • Fifth Generation Languages
 Declarative languages 
 Functional(?): Lisp, Scheme, SML
 ◦ Also called applicative 
◦ Everything is a function 
Logic: Prolog
 ◦ Based on mathematical logic 
◦ Rule- or Constraint-based

Programming Languages
Two broad groups
 1. Traditional programming languages 
 Sequences of instructions 
 First, second and some third generation languages 
2.  Object-oriented languages
  Objects are created rather than sequences of instructions
  Some third generation, and fourth and fifth generation languages
  • Traditional Programming Languages
  1.  FORTRAN ◦ FORmula TRANslation. ◦ Developed at IBM in the mid-1950s. ◦ Designed for scientific and mathematical applications by scientists and engineers.
  2.  COBOL ◦ COmmon Business Oriented Language. ◦ Developed in 1959. ◦ Designed to be common to many different computers. ◦ Typically used for business applications.
  3.  BASIC ◦ Beginner’s All-purpose Symbolic Instruction Code. ◦ Developed at Dartmouth College in mid 1960s. ◦ Developed as a simple language for students to write programs with which they could interact through terminals.
  4. C ◦ Developed by Bell Laboratories in the early 1970s. ◦ Provides control and efficiency of assembly language while having third generation language features. ◦ Often used for system programs. ◦ UNIX is written in C. 
  • Object Oriented Programming Languages
  1. C++ ◦ It is C language with additional features. ◦ Widely used for developing system and application software. ◦ Graphical user interfaces can be developed easily with visual programming tools.
  2. JAVA ◦ An object-oriented language similar to C++ that eliminates lots of C++’s problematic features ◦ Allows a web page developer to create programs for applications, called applets that can be used through a browser. ◦ Objective of JAVA developers is that it be machine, platform and operating system independent.
  • Special Programming Languages
  1.  Scripting Languages ◦ JavaScript and VBScript ◦ Php and ASP ◦ Perl and Python 
  2. Command Languages ◦ sh, csh, bash 
  3.  Text processing Languages ◦ LaTex, PostScript
  4.  HTML ◦ HyperText Markup Language. ◦ Used on the Internet and the World Wide Web (WWW). ◦ Web page developer puts brief codes called tags in the page to indicate how the page should be formatted.
  • Criteria in good Language Design
  1.  Writability: The quality of a language that enables a programmer to use it to express a computation clearly, correctly, concisely, and quickly. 
  2.  Readability: The quality of a language that enables a programmer to understand and comprehend the nature of a computation easily and accurately. 
  3.  Orthogonality: The quality of a language that features provided have as few restrictions as possible and be combinable in any meaningful way. 
  4.  Reliability: The quality of a language that assures a program will not behave in unexpected or disastrous ways during execution. 
  5.  Maintainability: The quality of a language that eases errors can be found and corrected and new features added.
  6. Generality: The quality of a language that avoids special cases in the availability or use of constructs and by combining closely related constructs into a single more general one. 
  7.  Uniformity: The quality of a language that similar features should look similar and behave similar.
  8. Extensibility: The quality of a language that provides some general mechanism for the user to add new constructs to a language. 
  9. Standardability: The quality of a language that allows programs written to be transported from one computer to another without significant change in language structure. 
  10. Implementability: The quality of a language that provides a translator or interpreter can be written. This can address to complexity of the language definition.

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