Introduction to C programming

C is a general-purpose, high-level language that was originally developed by Dennis M. Ritchie to develop the UNIX operating system at Bell Labs. C was first implemented on the DEC PDP-11 computer in 1972. The main features of C language include low-level access to memory, simple set of keywords, and clean style, these features make C language suitable for system programming like operating system or compiler development.Many later languages have borrowed syntax/features directly or indirectly from C language. Like syntax of Java, PHP, JavaScript and many other languages is mainly based on C language. C++ is nearly a superset of C language having object oriented features.




Ken Thompson (left) with Dennis Ritchie (right, the inventor of the C programming language)

In 1978, Brian Kernighan and Dennis Ritchie produced the first publicly available description of C, now known as the K&R standard.When C was first written the standard was set by its authors Kernighan and Ritche - hence "K&R C". In 1990, an international ANSI standard for C was established which differs from K & R C in a number of ways. The C standard is ISO/IEC 9899:2011, also known as C11 as the final draft was published in 2011. Before C11, there was C99. The C11 final draft is available here. See this for complete history of C standards.
  • The C programming language is a structure oriented programming language, developed at Bell Laboratories in 1972 by Dennis Ritchie
  • C programming language features were derived from an earlier language called “B” (Basic Combined Programming Language – BCPL)
  • C language was invented for implementing UNIX operating system
  • In 1978, Dennis Ritchie and Brian Kernighan published the first edition “The C Programming Language” and commonly known as K&R C
  • In 1983, the American National Standards Institute (ANSI) established a committee to provide a modern, comprehensive definition of C. The resulting definition, the ANSI standard, or “ANSI C”, was completed late 1988.
C programming language standards:
  • C89/C90 standard – First standardized specification for C language was developed by the American National Standards Institute in 1989. C89 and C90 standards refer to the same programming language.
  • C99 standard – Next revision was published in 1999 that introduced new features like advanced data types and other changes.
  • C11 was officially published on Dec 8 2018 provides unicode support and multi threading
  • C17.As of Oct 2018 C17 is the current standard for C Programming Languages.C17 addresses defects in C11 without introducing new language features.
  • C2x is an informal name for the next (after C17) major C language standard revision. It is not expected to be voted on until 2021
C11 and Embedded C language:
  • C11 standard adds new features to C programming language and library like type generic macros, anonymous structures, improved Unicode support, atomic operations, multi-threading and bounds-checked functions. It also makes some portions of the existing C99 library optional and improves compatibility with C++.
  • Embedded C includes features not available in C like fixed-point arithmetic, named address spaces, and basic I/O hardware addressing.
  • Operating systems, C compiler and all UNIX application programs are written in C language
  • It is also called as procedure oriented programming language. The C language is reliable, simple and easy to use. C has been coded in assembly language.
Features of C programming language:
C language is one of the powerful language. Below are some of the features of C language.
  • Reliability
  • Portability
  • Flexibility
  • Interactivity
  • Modularity
  • Efficiency and Effectiveness
Uses of C programming language:
The C programming language is used for developing system applications that forms a major portion of operating systems such as Windows, UNIX and Linux. Below are some examples of C being used.
  • Database systems
  • Graphics packages
  • Word processors
  • Spreadsheets
  • Operating system development
  • Compilers and Assemblers
  • Network drivers
  • Interpreters
Which level is C language belonging to?
There are 3 levels of programming languages. They are,
  1. Middle Level languages:
    Middle level languages don’t provide all the built-in functions found in high level languages, but provides all building blocks that we need to produce the result we want. Examples: C, C++
  2. High Level languages:
    High level languages provide almost everything that the programmer might need to do as already built into the language. Example: Java, Python
  3. Low Level languages:
    Low level languages provides nothing other than access to the machines basic instruction set. Example: Assembler
C language is a structured language:
Structure oriented language:
  • In this type of language, large programs are divided into small programs called functions
  • Prime focus is on functions and procedures that operate on the data
  • Data moves freely around the systems from one function to another
  • Program structure follows “Top Down Approach”
  • Examples: C, Pascal, ALGOL and Modula-2
Object oriented language:
  • In this type of language, programs are divided into objects
  • Prime focus is in the data that is being operated and not on the functions or procedures
  • Data is hidden and cannot be accessed by external functions
  • Program structure follows “Bottom UP Approach”
  • Examples: C++, JAVA and C# (C sharp)
Non structure oriented language:
  • There is no specific structure for programming this language. Examples: BASIC, COBOL, FORTRAN
Key points to remember in C language:
  • The C language is a structure oriented programming language developed by Dennis Ritchie.
  • The C language is belonging to middle level programming language.
  • C was invented to write an operating system called UNIX.
  • C is a successor of B language which was introduced around the early 1970s.
  • The language was formalized in 1988 by the American National Standard Institute (ANSI).
  • The UNIX OS was totally written in C.
  • Today C is the most widely used and popular System Programming Language.
  • Most of the state-of-the-art software have been implemented using C.
  • Today's most popular Linux OS and RDBMS MySQL have been written in C.
  • Operating system programs such as Windows, Unix, Linux are written in C language.
  • C89/C90 and C99 are two standardized editions of C language.
  • C has been written in assembly language.



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