Introduction to C programming

Introduction to the C Programming Language

C is a general-purpose, high-level programming language originally developed by Dennis M. Ritchie at Bell Labs to build the UNIX operating system.

C was first implemented in 1972 on the DEC PDP-11 computer.

Key Features of C Language

  • Provides low-level access to memory

  • Has a simple and small set of keywords

  • Follows a clean and structured programming style

These features make C highly suitable for:

  • System programming

  • Operating system development

  • Compiler development

Influence on Other Programming Languages

Many modern programming languages have borrowed syntax and features from C, either directly or indirectly.

Examples include:

  • Java

  • PHP

  • JavaScript

C++ is almost a superset of C, adding object-oriented programming features while retaining most of C’s functionality.





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

History and Standards of the C Programming 

Language

Early Development

  • The C programming language was developed in 1972 at Bell Laboratories by Dennis Ritchie.

  • C was derived from an earlier language called B, which itself came from BCPL (Basic Combined Programming Language).

  • C was invented primarily to implement the UNIX operating system.

  • The UNIX OS, C compilers, and many UNIX applications were written in C.

K&R C (First Description)

  • In 1978, Dennis Ritchie and Brian Kernighan published the book
    “The C Programming Language.”

  • This became the first widely available specification of C.

  • The version described in this book is known as K&R C.

ANSI Standardization

  • In 1983, the American National Standards Institute (ANSI) formed a committee to standardize C.

  • The ANSI C standard was completed in 1988.

  • This version differed from K&R C in several ways and provided a modern, formal definition of the language.

C Language Standards Timeline

✔ C89 / C90

  • First standardized specification

  • Developed by ANSI in 1989

  • C89 and C90 refer to the same standard

✔ C99

  • Published in 1999

  • Introduced:

    • New data types

    • Language improvements

    • Library enhancements

✔ C11

  • Final draft published in 2011

  • ISO standard: ISO/IEC 9899:2011

  • Added features such as:

    • Unicode support improvements

    • Multi-threading support

    • Atomic operations

    • Type-generic macros

    • Anonymous structures

    • Bounds-checked functions

  • Some C99 library portions became optional

  • Improved compatibility with C++

✔ C17

  • Published October 2018

  • Fixes defects in C11

  • No major new language features

✔ C2x (Next Standard)

  • Informal name for the revision after C17

  • Planned future update (timeline initially expected around 2021)

C11 and Embedded C

C11 Adds

  • Type-generic macros

  • Anonymous structures

  • Better Unicode support

  • Multi-threading

  • Atomic operations

  • Safer functions

Embedded C Includes Extra Features

  • Fixed-point arithmetic

  • Named address spaces

  • Direct hardware I/O addressing

Nature of the C Programming Language

  • Structured-oriented language

  • Procedure-oriented programming language

  • Middle-level programming language

  • Known for being:

    • Reliable

    • Simple

    • Efficient

    • Easy to use

C was originally implemented using assembly language.

Features of C Programming Language

  • Reliability

  • Portability

  • Flexibility

  • Interactivity

  • Modularity

  • Efficiency and effectiveness

Uses of C Programming Language

C is widely used for system and application software, including:

  • Operating system development (Windows, UNIX, Linux)

  • Database systems

  • Graphics packages

  • Word processors

  • Spreadsheets

  • Compilers and assemblers

  • Network drivers

  • Interpreters

Examples:

  • Linux OS written largely in C

  • MySQL database implemented in C

Levels of Programming Languages

1️⃣ Middle-Level Languages

  • Provide building blocks for programming

  • Offer both low-level and high-level features

Examples: C, C++

2️⃣ High-Level Languages

  • Provide many built-in functions

  • Easier for programmers to use

Examples: Java, Python

3️⃣ Low-Level Languages

  • Provide direct access to machine instructions

Example: Assembly language

C as a Structured Language

Structure-Oriented Languages

  • Large programs divided into functions

  • Focus on procedures/functions operating on data

  • Data moves between functions freely

  • Uses Top-Down approach

Examples: C, Pascal, ALGOL, Modula-2

Object-Oriented Languages

  • Programs divided into objects

  • Focus on data

  • Data is hidden (encapsulation)

  • Uses Bottom-Up approach

Examples: C++, Java, C#

Non-Structured Languages

  • No strict programming structure

Examples: BASIC, COBOL, FORTRAN

Key Points to Remember About C

  • Developed by Dennis Ritchie

  • Created to write UNIX operating system

  • Successor of B language

  • Standardized by ANSI in 1988

  • Belongs to middle-level programming languages

  • Widely used for system programming

  • Many modern software systems use C

  • Operating systems like Windows, UNIX, Linux use C

  • Major standardized versions include:

    • C89/C90

    • C99

    • C11

    • C17




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