Programming C: Part 1

C (pronounced /siː/, like the letter C) is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system.

Although C was designed for implementing system software,  it is also widely used for developing portable application software.

C is one of the most widely used programming languages of all time and there are very few computer architectures for which a C compiler does not exist. C has greatly influenced many other popular programming languages, most notably C++, which began as an extension to C.

C is an imperative (procedural) systems implementation language. It was designed to be compiled using a relatively straightforward compiler, to provide low-level access to memory, to provide language constructs that map efficiently to machine instructions, and to require minimal run-time support. C was therefore useful for many applications that had formerly been coded in assembly language.

Despite its low-level capabilities, the language was designed to encourage cross-platform programming. A standards-compliant and portably written C program can be compiled for a very wide variety of computer platforms and operating systems with few changes to its source code. The language has become available on a very wide range of platforms, from embedded micro controllers to supercomputers.

Like most imperative languages in the ALGOL tradition, C has facilities for structured programming and allows lexical variable scope and recursion, while a static type system prevents many unintended operations. In C, all executable code is contained within functions. Function parameters are always passed by value. Pass-by-reference is simulated in C by explicitly passing pointer values. Heterogeneous aggregate data types (struct) allow related data elements to be combined and manipulated as a unit. C program source text is free-format, using the semicolon as a statement terminator.

C also exhibits the following more specific characteristics:

• Partially weak typing; for instance, characters can be used as integers
• Low-level access to computer memory by converting machine addresses to typed pointers
• Function and data pointers supporting ad hocrun-time polymorphism
• array indexing as a secondary notion, defined in terms of pointer arithmetic
• A preprocessor for macro definition, source code file inclusion, and conditional compilation
• Complex functionality such as I/O, string manipulation, and mathematical functions consistently delegated to library routines
• A large number of compound operators, such as +=, -=, *=, ++, etc.