Programing language & its functions

[Audio] Programing language and its functions. Presented by Rrapo Gremi..

[Audio] What is a programing language? A programming language is an artificial language that can be used to control the behavior of a machine, particularly a computer. Programming languages, like human languages, are defined through the use of syntactic and semantic rules, to determine structure and meaning respectively. Programming languages are used to facilitate communication about the task of organizing and manipulating information, and to express algorithms precisely. Some authors restrict the term "programming language" to those languages that can express all possible algorithms; sometimes the term " computer language" is used for more limited artificial languages. Thousands of different programming languages have been created, and new ones are created every year..

[Audio] Definitions Authors disagree on the precise definition, but traits often considered important requirements and objectives of the language to be characterized as a programming language: Function: A programming language is a language used to write computer programs, which instruct a computer to perform some kind of computation, and/or organize the flow of control between external devices (such as a printer, a robot, or any peripheral). Target: Programming languages differ from natural languages in that natural languages are only used for interaction between people, while programming languages also allow humans to communicate instructions to machines. In some cases, programming languages are used by one program or machine to program another; PostScript source code, for example, is frequently generated programmatically to control a computer printer or display..

[Audio] Definitions. Constructs : Programming languages may contain constructs for defining and manipulating data structures or for controlling the flow of execution. Expressive power : The theory of computation classifies languages by the computations they can express (see Chomsky hierarchy). All Turing complete languages can implement the same set of algorithms. ANSI/ ISO SQL and Charity are examples of languages that are not Turing complete yet often called programming languages..

[Audio] The purpose. A prominent purpose of programming languages is to provide instructions to a computer. As such, programming languages differ from most other forms of human expression in that they require a greater degree of precision and completeness. When using a natural language to communicate with other people, human authors and speakers can be ambiguous and make small errors, and still expect their intent to be understood. However, computers do exactly what they are told to do, and cannot understand the code the programmer "intended" to write. The combination of the language definition, the program, and the program's inputs must fully specify the external behavior that occurs when the program is executed. Many languages have been designed from scratch, altered to meet new needs, combined with other languages, and eventually fallen into disuse. Although there have been attempts to design one "universal" computer language that serves all purposes, all of them have failed to be accepted in this role. The need for diverse computer languages arises from the diversity of contexts in which languages are used:.

[Audio] Programs range from tiny scripts written by individual hobbyists to huge systems written by hundreds of programmers. Programmers range in expertise from novices who need simplicity above all else, to experts who may be comfortable with considerable complexity. Programs must balance speed, size, and simplicity on systems ranging from microcontrollers to supercomputers. Programs may be written once and not change for generations, or they may undergo nearly constant modification. Finally, programmers may simply differ in their tastes: they may be accustomed to discussing problems and expressing them in a particular language..

[Audio] Syntax.. Syntax.

[Audio] A programming language's surface form is known as its syntax. Most programming languages are purely textual; they use sequences of text including words, numbers, and punctuation, much like written natural languages. On the other hand, there are some programming languages which are more graphical in nature, using spatial relationships between symbols to specify a program. The syntax of a language describes the possible combinations of symbols that form a syntactically correct program. The meaning given to a combination of symbols is handled by semantics. Since most languages are textual, this article discusses textual syntax..

[Audio] Programming language syntax is usually defined using a combination of regular expressions (for lexical structure) and Backus-Naur Form (for grammatical structure). Below is a simple grammar, based on Lisp: This grammar specifies the following: an expression is either an atom or a list; an atom is either a number or a symbol; a number is an unbroken sequence of one or more decimal digits, optionally preceded by a plus or minus sign; a symbol is a letter followed by zero or more of any characters (excluding whitespace); and a list is a matched pair of parentheses, with zero or more expressions inside it..

[Audio] Type system. A type system defines how a programming language classifies values and expressions into types, how it can manipulate those types and how they interact. This generally includes a description of the data structures that can be constructed in the language. The design and study of type systems using formal mathematics is known as type theory. Internally, all data in modern digital computers are stored simply as zeros or ones ( binary). The data typically represent information in the real world such as names, bank accounts and measurements, so the low-level binary data are organized by programming languages into these high-level concepts as data types. There are also more types whose purpose is just to warn the programmer about semantically meaningless statements or verify safety properties of programs. Languages can be classified with respect to their type systems..

[Audio] Weak and strong typing. Weak. Weak typing allows a value of one type to be treated as another, for example treating a string as a number. (C++) An alternate definition for "weakly typed" refers to languages, such as Perl, JavaScript, and C++ which permit a large number of implicit type conversions. Strong. Strong typing prevents the above. Attempting to mix types raises an error. Strongly-typed languages are often termed type-safe or safe, but they do not make bugs impossible. Ada, Python, and ML are strongly typed. Strong and static are generally considered orthogonal concepts, but usage in the literature differs..

[Audio] Execution Semantics. Once data has been specified, the machine must be instructed to perform operations on the data. The execution semantics of a language defines how and when the various constructs of a language should produce a program behavior. For example, the semantics may define the strategy by which expressions are evaluated to values, or the manner in which control structures conditionally execute statements..

[Audio] Core Library. Most programming languages have an associated core library (sometimes known as the 'Standard library', especially if it is included as part of the published language standard), which is conventionally made available by all implementations of the language. Core libraries typically include definitions for commonly used algorithms, data structures, and mechanisms for input and output. A language's core library is often treated as part of the language by its users, although the designers may have treated it as a separate entity. Many language specifications define a core that must be made available in all implementations, and in the case of standardized languages this core library may be required. The line between a language and its core library therefore differs from language to language. Indeed, some languages are designed so that the meanings of certain syntactic constructs cannot even be described without referring to the core library..

[Audio] Practice. A language's designers and users must construct a number of artifacts that govern and enable the practice of programming. The most important of these artifacts are the language specification and implementation. Specification The specification of a programming language is intended to provide a definition that language users and implementors can use to interpret the behavior of programs when reading their source code. A programming language specification can take several forms, including the following: An explicit definition of the syntax and semantics of the language. While syntax is commonly specified using a formal grammar, semantic definitions may be written in natural language (e.g., the C language), or a formal semantics (e.g., the Standard ML and Scheme specifications). A description of the behavior of a translator for the language (e.g., the C++ and Fortran). The syntax and semantics of the language has to be inferred from this description, which may be written in natural or a formal language. A model implementation, sometimes written in the language being specified (e.g., Prolog). The syntax and semantics of the language are explicit in the behavior of the model implementation..

[Audio] Implimantation. An implementation of a programming language provides a way to execute that program on one or more configurations of hardware and software. There are, broadly, two approaches to programming language implementation: compilation and interpretation. It is generally possible to implement a language using both techniques. The output of a compiler may be executed by hardware or a program called an interpreter. In some implementations that make use of the interpreter approach there is no distinct boundary between compiling and interpreting. For instance, some implementations of the BASIC programming language compile and then execute the source a line at a time. Programs that are executed directly on the hardware usually run several orders of magnitude faster than those that are interpreted in software. One technique for improving the performance of interpreted programs is just-in-time compilation. Here the virtual machine monitors which sequences of bytecode are frequently executed and translates them to machine code for direct execution on the hardware..

[Audio] Taxonomies. There is no overarching classification scheme for programming languages. A given programming language does not usually have a single ancestor language. Languages commonly arise by combining the elements of several predecessor languages with new ideas in circulation at the time. Ideas that originate in one language will diffuse throughout a family of related languages, and then leap suddenly across familial gaps to appear in an entirely different family. The task is further complicated by the fact that languages can be classified along multiple axes. For example, Java is both an object-oriented language (because it encourages object-oriented organization) and a concurrent language (because it contains built-in constructs for running multiple threads in parallel). Python is an object-oriented scripting language. In broad strokes, programming languages divide into programming paradigms and a classification by intended domain of use. Paradigms include procedural programming, object-oriented programming, functional programming, and logic programming; some languages are hybrids of paradigms or multi-paradigmatic. An assembly language is not so much a paradigm as a direct model of an underlying machine architecture. By purpose, programming languages might be considered general purpose, system programming languages, scripting languages, domain-specific languages, or concurrent/distributed languages (or a combination of these). Some general purpose languages were designed largely with educational goals..

[Audio] Thank you for you attention.. Thank you. Reference : https://www.cs.mcgill.ca/~rwest/wikispeedia/wpcd/wp/p/Programming_language.htm.