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Watch this to learn about Sophia the humanoid robot of Hanson Robotics

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C Programming C is a general-purpose, procedural computer programming language which is still in regular use over four decades after its creation. It was developed in 1972 by Dennis Ritchie and Brian Kernighan (then of Bell Laboratories) for use with the Unix operating system, and was documented, before it entered the standards process, in a 1978 reference book commonly referred to as the Kernighan and Ritchie book, or just K&R. The language has been implemented for many different computer platforms and eventually became standardized by ANSI and ISO--there is a Second Edition of K&R using the ANSI standard syntax. Although superseded by more modern languages for general application programming, since 2010 versions of C are still being used, primarily for writing operating system software and embedded programs (for gadgets such as smart phones). C and its closely related sister language, C++, are also used for games development and other graphics- or media-intensive programming. Although once used for web programming, it has been superseded for web programming by newer languages that provide more security and which enforce safer programming practices. How is the World Powered by C? Despite the prevalence of higher-level languages, C continues to empower the world. The following are some of the systems that are used by millions and are programmed in the C language. Microsoft Windows Microsoft’s Windows kernel is developed mostly in C, with some parts in assembly language. For decades, the world’s most used operating system, with about 90 percent of the market share, has been powered by a kernel written in C. Linux Linux is also written mostly in C, with some parts in assembly. About 97 percent of the world’s 500 most powerful supercomputers run the Linux kernel. It is also used in many personal computers. Mac Mac computers are also powered by C, since the OS X kernel is written mostly in C. Every program and driver in a Mac, as in Windows and Linux computers, is running on a C-powered kernel. Mobile iOS, Android and Windows Phone kernels are also written in C. They are just mobile adaptations of existing Mac OS, Linux and Windows kernels. So smartphones you use every day are running on a C kernel. Embedded Systems Imagine that you wake up one day and go shopping. The alarm clock that wakes you up is likely programmed in C. Then you use your microwave or coffee maker to make your breakfast. They are also embedded systems and therefore are probably programmed in C. You turn on your TV or radio while you eat your breakfast. Those are also embedded systems, powered by C. When you open your garage door with the remote control you are also using an embed  ded system that is most likely programmed in C. Then you get into your car. If it has the following features, also programmed in C: • automatic transmission • tire pressure detection systems • sensors (oxygen, temperature, oil level, etc.) • memory for seats and mirror settings. • dashboard display • anti-lock brakes • automatic stability control • cruise control • climate control • child-proof locks • keyless entry • heated seats • airbag control You get to the store, park your car and go to a vending machine to get a soda. What language did they use to program this vending machine? Probably C. Then you buy something at the store. The cash register is also programmed in C. And when you pay with your credit card? You guessed it: the credit card reader is, again, likely programmed in C. Syntax C has a formal grammar specified by the C standard. Line endings are generally not significant in C; however, line boundaries do have significance during the preprocessing phase. Comments may appear either between the delimiters /* and */, or (since C99) following // until the end of the line. Comments delimited by /* and */ do not nest, and these sequences of characters are not interpreted as comment delimiters if they appear inside string or character literals. C source files contain declarations and function definitions. Function definitions, in turn, contain declarations and statements. Declarations either define new types using keywords such as struct, union, and enum, or assign types to and perhaps reserve storage for new variables, usually by writing the type followed by the variable name. Keywords such as char and int specify built-in types. Sections of code are enclosed in braces ({ and }, sometimes called "curly brackets") to limit the scope of declarations and to act as a single statement for control structures. As an imperative language, C uses statements to specify actions. The most common statement is an expression statement, consisting of an expression to be evaluated, followed by a semicolon; as a side effect of the evaluation, functions may be called and variables may be assigned new values. To modify the normal sequential execution of statements, C provides several control-flow statements identified by reserved keywords. Structured programming is supported by if(-else) conditional execution and by do-while, while, and for iterative execution (looping). The for statement has separate initialization, testing, and reinitialization expressions, any or all of which can be omitted. break and continue can be used to leave the innermost enclosing loop statement or skip to its reinitialization. There is also a non-structured goto statement which branches directly to the designated label within the function. Switch selects a case to be executed based on the value of an integer expression. Expressions can use a variety of built-in operators and may contain function calls. The order in which arguments to functions and operands to most operators are evaluated is unspecified. The evaluations may even be interleaved. However, all side effects (including storage to variables) will occur before the next "sequence point"; sequence points include the end of each expression statement, and the entry to and return from each function call. Sequence points also occur during evaluation of expressions containing certain operators (&&, ||, ?: and the comma operator). This permits a high degree of object code optimization by the compiler, but requires C programmers to take more care to obtain reliable results than is needed for other programming languages. Kernighan and Ritchie say in the Introduction of The C Programming Language: "C, like any other language, has its blemishes. Some of the operators have the wrong precedence; some parts of the syntax could be better. The C standard did not attempt to correct many of these blemishes, because of the impact of such changes on already existing software. Character set The basic C source character set includes the following characters: • Lowercase and uppercase letters of ISO Basic Latin Alphabet: a–z A–Z • Decimal digits: 0–9 • Graphic characters: ! " # % & ' ( ) * + , - . / : ; < = > ? [ \ ] ^ _ { | } ~ • Whitespace characters: space, horizontal tab, vertical tab, form feed, newline Newline indicates the end of a text line; it need not correspond to an actual single character, although for convenience C treats it as one. Additional multi-byte encoded characters may be used in string literals, but they are not entirely portable. The latest C standard (C11) allows multi-national Unicode characters to be embedded portably within C source text by using \uXXXX or \UXXXXXXXX encoding (where the X denotes a hexadecimal character), although this feature is not yet widely implemented. The basic C execution character set contains the same characters, along with representations for alert, backspace, and carriage return. Run-time support for extended character sets has increased with each revision of the C standard. Reserved words C89 has 32 reserved words, also known as keywords, which are the words that cannot be used for any purposes other than those for which they are predefined: auto break case char const continue default do double else enum extern float for goto if int long register return short signed sizeof static struct switch typedef union unsigned void volatile while C99 reserved five more words: _Bool _Complex _Imaginary inline restrict C11 reserved seven more words: _Alignas _Alignof _Atomic _Generic _Noreturn _Static_assert _Thread_local Most of the recently reserved words begin with an underscore followed by a capital letter, because identifiers of that form were previously reserved by the C standard for use only by implementations. Since existing program source code should not have been using these identifiers, it would not be affected when C implementations started supporting these extensions to the programming language. Some standard headers do define more convenient synonyms for underscored identifiers. The language previously included a reserved word called entry, but this was seldom implemented, and has now been removed as a reserved word. Operators Main article: Operators in C and C++ C supports a rich set of operators, which are symbols used within an expression to specify the manipulations to be performed while evaluating that expression. C has operators for: • arithmetic: +, -, *, /, % • assignment: = • augmented assignment: +=, -=, *=, /=, %=, &=, |=, ^=, <<=, >>= • bitwise logic: ~, &, |, ^ • bitwise shifts: <<, >> • boolean logic: !, &&, || • conditional evaluation: ? : • equality testing: ==, != • calling functions: ( ) • increment and decrement: ++, -- • member selection: ., -> • object size: sizeof • order relations: <, <=, >, >= • reference and dereference: &, *, [ ] • sequencing: , • subexpression grouping: ( ) • type conversion: (typename) C uses the operator = (used in mathematics to express equality) to indicate assignment, following the precedent of Fortran and PL/I, but unlike ALGOL and its derivatives. C uses the operator == to test for equality. The similarity between these two operators (assignment and equality) may result in the accidental use of one in place of the other, and in many cases, the mistake does not produce an error message (although some compilers produce warnings). For example, the conditional expression if(a==b+1) might mistakenly be written as if(a=b+1), which will be evaluated as true if a is not zero after the assignment. The C operator precedence is not always intuitive. For example, the operator == binds more tightly than (is executed prior to) the operators & (bitwise AND) and | (bitwise OR) in expressions such as x & 1 == 0, which must be written as (x & 1) == 0 if that is the coder's intent. What are the disadvantages of C Programming Language • C Programming Language doesn't support Object Oriented Programming (OOP) features like Inheritance, Encapsulation, Polymorphism etc. It is a procedure oriented language. In C, we have to implement any algorithms as a set of function calls. • C doesn't perform Run Time Type Checking. It only does compile time type checking. At run time, C doesn't ensure whether correct data type is used instead it perform automatic type conversion. • C does not provides support for namespace like C++. Without Namespace, we cannot declare two variables of same name. • C doesn't support the concept of constructors and destructors. Conclusion The C programming language doesn’t seem to have an expiration date. It’s closeness to the hardware, great portability and deterministic usage of resources makes it ideal for low level development for such things as operating system kernels and embedded software. Its versatility, efficiency and good performance makes it an excellent choice for high complexity data manipulation software, like databases or 3D animation. The fact that many programming languages today are better than C for their intended use doesn’t mean that they beat C in all areas. C is still unsurpassed when performance is the priority. The world is running on C-powered devices. We use these devices every day whether we realize it or not. C is the past, the present, and, as far as we can see, still the future for many areas of software.

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