C Programming Language Tutorial Part 1 Introduction

C was originally developed by Dennis Ritchie between 1969 and 1973 at AT&T Bell Labs,[5] and used to re-implement the Unix operating system.[6] It has since become one of the most widely used programming languages of all time,[7][8] with C compilers from various vendors available for the majority of existing computer architectures and operating systems. C has been standardized by the American National Standards Institute (ANSI) since 1989 (see ANSI C) and subsequently by the International Organization for Standardization (ISO).

Many later languages have borrowed directly or indirectly from C, including C++, D, Go, Rust, Java, JavaScript, Limbo, LPC, C#, Objective-C, Perl, PHP, Python, Verilog (hardware description language),[4] and Unix's C shell. These languages have drawn many of their control structures and other basic features from C, usually with overall syntactical similarity to C that sometimes includes identical simple control structures.[9][10][11] C is also used as an intermediate language for other languages,[12] and for building standard libraries and runtime systems for higher-level languages, such as CPython.

The C language also exhibits the following characteristics:

There is a small, fixed number of keywords, including a full set of flow of control primitives: for, if/else, while, switch, and do/while. There is one namespace, and user-defined names are not distinguished from keywords by any kind of sigil.
There are a large number of arithmetical and logical operators, such as +, +=, ++, &, ~, etc.
More than one assignment may be performed in a single statement.
Function return values can be ignored when not needed.
Typing is static, but weakly enforced: all data has a type, but implicit conversions can be performed; for instance, characters can be used as integers.
Declaration syntax mimics usage context. C has no "define" keyword; instead, a statement beginning with the name of a type is taken as a declaration. There is no "function" keyword; instead, a function is indicated by the parentheses of an argument list.
User-defined (typedef) and compound types are possible.
Heterogeneous aggregate data types (struct) allow related data elements to be accessed and assigned as a unit.
Array indexing is a secondary notation, defined in terms of pointer arithmetic. Unlike structs, arrays are not first-class objects; they cannot be assigned or compared using single built-in operators. There is no "array" keyword, in use or definition; instead, square brackets indicate arrays syntactically, for example month[11].
Enumerated types are possible with the enum keyword. They are not tagged, and are freely interconvertible with integers.
Strings are not a separate data type, but are conventionally implemented as null-terminated arrays of characters.
Low-level access to computer memory is possible by converting machine addresses to typed pointers.
Procedures (subroutines not returning values) are a special case of function, with an untyped return type void.
Functions may not be defined within the lexical scope of other functions.
Function and data pointers permit ad hoc run-time polymorphism.
A preprocessor performs macro definition, source code file inclusion, and conditional compilation.
There is a basic form of modularity: files can be compiled separately and linked together, with control over which functions and data objects are visible to other files via static and extern attributes.
Complex functionality such as I/O, string manipulation, and mathematical functions are consistently delegated to library routines.
C does not include some features found in newer, more modern high-level languages, including object orientation and garbage collection.

Data types in C
Fundamental Data Types
Integer types
Floating Type
Character types
Derived Data Types
Arrays
Pointers
Structures
Enumeration