/ June 2018; 1 year ago ( 2018-06),.c,.hMajorK&R,Influenced by(, ),Influenced:, (HDL),. at WikibooksC (, as in the ) is a, computer supporting, and, while a prevents unintended operations. By design, C provides constructs that map efficiently to typical, and has found lasting use in applications previously coded in. Such applications include, as well as various for computers ranging from to.C was originally developed at by between 1972 and 1973 to make utilities running on. Later, it was applied to re-implementing the kernel of the Unix operating system.

1. C&c Generals Zero Hour Maps

During the 1980s, C gradually gained popularity. Nowadays, it is one of the, with C from various vendors available for the majority of existing and operating systems. C has been standardized by the since 1989 (see ) and subsequently by the.C is an language. It was designed to be compiled using a relatively straightforward, to provide access to, to provide language constructs that map efficiently to, and to require minimal. Despite its low-level capabilities, the language was designed to encourage programming.

A -compliant C program that is written with in mind can be compiled for a wide variety of computer platforms and operating systems with few changes to its source code; the language has become available on various platforms, from embedded to. (right), the inventor of the C programming language, withLike most procedural languages in the tradition, C has facilities for and allows and recursion. Its static prevents unintended operations. In C, all is contained within (also called 'functions', though not strictly in the sense of ). Are always passed by value. Pass-by-reference is simulated in C by explicitly passing values. C program source text is, using the as a terminator and for grouping.The C language also exhibits the following characteristics:.

There is a small, fixed number of keywords, including a full set of primitives:,. User-defined names are not distinguished from keywords by any kind of. There are a large number of arithmetic, bitwise and logic operators: +, +=, , &, etc. More than one may be performed in a single statement. Function return values can be ignored when not needed. Typing is, but; all data has a type, but implicit conversions are possible. 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 ( ) and compound types are possible. Heterogeneous aggregate data types ( ) allow related data elements to be accessed and assigned as a unit. is a structure with overlapping members; only the last member stored is valid. 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 month11. are possible with the enum keyword. The cover of the book The C Programming Language, first edition, by andIn 1978, and published the first edition of. This book, known to C programmers as 'K&R', served for many years as an informal of the language. The version of C that it describes is commonly referred to as K&R C. Main article:During the late 1970s and 1980s, versions of C were implemented for a wide variety of, and, including the, as its popularity began to increase significantly.In 1983, the (ANSI) formed a committee, X3J11, to establish a standard specification of C.

C&c Generals Zero Hour Maps

X3J11 based the C standard on the Unix implementation; however, the non-portable portion of the Unix C library was handed off to the 1003 to become the basis for the 1988 standard. In 1989, the C standard was ratified as ANSI X3.159-1989 'Programming Language C'. This version of the language is often referred to as, Standard C, or sometimes C89.In 1990, the ANSI C standard (with formatting changes) was adopted by the (ISO) as ISO/IEC 9899:1990, which is sometimes called C90. Therefore, the terms 'C89' and 'C90' refer to the same programming language.ANSI, like other national standards bodies, no longer develops the C standard independently, but defers to the international C standard, maintained by the working group /WG14. National adoption of an update to the international standard typically occurs within a year of ISO publication.One of the aims of the C standardization process was to produce a of K&R C, incorporating many of the subsequently introduced unofficial features. The standards committee also included several additional features such as (borrowed from C), void pointers, support for international and, and preprocessor enhancements.

Although the for parameter declarations was augmented to include the style used in C, the K&R interface continued to be permitted, for compatibility with existing source code.C89 is supported by current C compilers, and most C code being written today is based on it. Any program written only in Standard C and without any hardware-dependent assumptions will run correctly on any with a conforming C implementation, within its resource limits. Main article:The C standard was further revised in the late 1990s, leading to the publication of ISO/IEC 9899:1999 in 1999, which is commonly referred to as '. It has since been amended three times by Technical Corrigenda.C99 introduced several new features, including, several new (including long long int and a complex type to represent ), and, improved support for floating point, support for (macros of variable ), and support for one-line comments beginning with //, as in or C. Many of these had already been implemented as extensions in several C compilers.C99 is for the most part backward compatible with C90, but is stricter in some ways; in particular, a declaration that lacks a type specifier no longer has int implicitly assumed.

A standard macro STDCVERSION is defined with value 199901L to indicate that C99 support is available., and other C compilers now support many or all of the new features of C99. The C compiler in, however, implements the C89 standard and those parts of C99 that are required for compatibility with. Main article:In 2007, work began on another revision of the C standard, informally called 'C1X' until its official publication on 2011-12-08. The C standards committee adopted guidelines to limit the adoption of new features that had not been tested by existing implementations.The C11 standard adds numerous new features to C and the library, including 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. The standard macro STDCVERSION is defined as 201112L to indicate that C11 support is available.C18. Main article:Historically, embedded C programming requires nonstandard extensions to the C language in order to support exotic features such as fixed-point arithmetic, multiple distinct memory banks, and basic I/O operations.In 2008, the C Standards Committee published a extending the C language to address these issues by providing a common standard for all implementations to adhere to.

It includes a number of features not available in normal C, such as, named address spaces, and basic I/O hardware addressing.Syntax. Alignas AlignofAtomic GenericNoreturn StaticassertThreadlocalMost 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:C supports a rich set of, which are symbols used within an to specify the manipulations to be performed while evaluating that expression.

C has operators for:.:,.: =.: +=, -=,.=, /=,%=, &=, =, ^=, =.: , &, , ^.:.:!, &&.:. equality testing:,.: ( ).: , -.:., -. object size:.:, =.: &,.

sequencing:.: ( ).: ( typename)C uses the operator = (used in mathematics to express equality) to indicate assignment, following the precedent of and, but unlike 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(ab+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 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.

'Hello, world' example The ' example, which appeared in the first edition of, has become the model for an introductory program in most programming textbooks, regardless of programming language. The program prints 'hello, world' to the, which is usually a terminal or screen display.The original version was. This section needs additional citations for. Unsourced material may be challenged and removed.Find sources: – ( October 2012) The in C is and, which makes it similar to the type system of descendants such as. There are built-in types for integers of various sizes, both signed and unsigned, and enumerated types ( enum). Integer type char is often used for single-byte characters. There are also derived types including, ( ), and ( union).C is often used in low-level systems programming where escapes from the type system may be necessary.

The compiler attempts to ensure type correctness of most expressions, but the programmer can override the checks in various ways, either by using a to explicitly convert a value from one type to another, or by using pointers or unions to reinterpret the underlying bits of a data object in some other way.Some find C's declaration syntax unintuitive, particularly for. (Ritchie's idea was to declare identifiers in contexts resembling their use: '.)C's usual arithmetic conversions allow for efficient code to be generated, but can sometimes produce unexpected results. For example, a comparison of signed and unsigned integers of equal width requires a conversion of the signed value to unsigned. This can generate unexpected results if the signed value is negative.Pointers C supports the use of, a type of that records the address or location of an object or function in memory. Pointers can be dereferenced to access data stored at the address pointed to, or to invoke a pointed-to function.

Pointers can be manipulated using assignment. The run-time representation of a pointer value is typically a raw memory address (perhaps augmented by an offset-within-word field), but since a pointer's type includes the type of the thing pointed to, expressions including pointers can be type-checked at compile time. Pointer arithmetic is automatically scaled by the size of the pointed-to data type. Pointers are used for many purposes in C.

Are commonly manipulated using pointers into arrays of characters. Is performed using pointers. Many data types, such as, are commonly implemented as dynamically allocated struct objects linked together using pointers.

Pointers to functions are useful for passing functions as arguments to (such as or ) or as to be invoked by event handlers.A value explicitly points to no valid location. Dereferencing a null pointer value is undefined, often resulting in a.

Null pointer values are useful for indicating special cases such as no 'next' pointer in the final node of a, or as an error indication from functions returning pointers. In appropriate contexts in source code, such as for assigning to a pointer variable, a null pointer constant can be written as 0, with or without explicit casting to a pointer type, or as the NULL macro defined by several standard headers. In conditional contexts, null pointer values evaluate to false, while all other pointer values evaluate to true.Void pointers ( void.) point to objects of unspecified type, and can therefore be used as 'generic' data pointers. Since the size and type of the pointed-to object is not known, void pointers cannot be dereferenced, nor is pointer arithmetic on them allowed, although they can easily be (and in many contexts implicitly are) converted to and from any other object pointer type.Careless use of pointers is potentially dangerous. Because they are typically unchecked, a pointer variable can be made to point to any arbitrary location, which can cause undesirable effects. Although properly used pointers point to safe places, they can be made to point to unsafe places by using invalid; the objects they point to may continue to be used after deallocation ; they may be used without having been initialized ; or they may be directly assigned an unsafe value using a cast, union, or through another corrupt pointer.

In general, C is permissive in allowing manipulation of and conversion between pointer types, although compilers typically provide options for various levels of checking. Some other programming languages address these problems by using more restrictive types.Arrays.

See also:types in C are traditionally of a fixed, static size specified at compile time. (The more recent C99 standard also allows a form of variable-length arrays.) However, it is also possible to allocate a block of memory (of arbitrary size) at run-time, using the standard library's malloc function, and treat it as an array. C's unification of arrays and pointers means that declared arrays and these dynamically allocated simulated arrays are virtually interchangeable.Since arrays are always accessed (in effect) via pointers, array accesses are typically not checked against the underlying array size, although some compilers may provide as an option. Array bounds violations are therefore possible and rather common in carelessly written code, and can lead to various repercussions, including illegal memory accesses, corruption of data, and run-time exceptions. If bounds checking is desired, it must be done manually.C does not have a special provision for declaring, but rather relies on within the type system to declare arrays of arrays, which effectively accomplishes the same thing. The index values of the resulting 'multi-dimensional array' can be thought of as increasing in.Multi-dimensional arrays are commonly used in numerical algorithms (mainly from applied ) to store matrices. The structure of the C array is well suited to this particular task.

However, since arrays are passed merely as pointers, the bounds of the array must be known fixed values or else explicitly passed to any subroutine that requires them, and dynamically sized arrays of arrays cannot be accessed using double indexing. (A workaround for this is to allocate the array with an additional 'row vector' of pointers to the columns.)C99 introduced 'variable-length arrays' which address some, but not all, of the issues with ordinary C arrays.Array–pointer interchangeability The subscript notation xi (where x designates a pointer) is for.(x+i). Taking advantage of the compiler's knowledge of the pointer type, the address that x + i points to is not the base address (pointed to by x) incremented by i bytes, but rather is defined to be the base address incremented by i multiplied by the size of an element that x points to. Thus, xi designates the i+1th element of the array.Furthermore, in most expression contexts (a notable exception is as operand of ), the name of an array is automatically converted to a pointer to the array's first element. This implies that an array is never copied as a whole when named as an argument to a function, but rather only the address of its first element is passed. Therefore, although function calls in C use semantics, arrays are in effect passed by.The size of an element can be determined by applying the operator sizeof to any dereferenced element of x, as in n = sizeof.x or n = sizeof x0, and the number of elements in a declared array A can be determined as sizeof A / sizeof A0. The latter only applies to array names: variables declared with subscripts ( int A20).

Due to the semantics of C, it is not possible to determine the entire size of arrays through pointers to arrays or those created by dynamic allocation ( ); code such as sizeof arr / sizeof arr0 (where arr designates a pointer) will not work since the compiler assumes the size of the pointer itself is being requested. Since array name arguments to sizeof are not converted to pointers, they do not exhibit such ambiguity. However, arrays created by dynamic allocation are accessed by pointers rather than true array variables, so they suffer from the same sizeof issues as array pointers.Thus, despite this apparent equivalence between array and pointer variables, there is still a distinction to be made between them. Even though the name of an array is, in most expression contexts, converted into a pointer (to its first element), this pointer does not itself occupy any storage; the array name is not an, and its address is a constant, unlike a pointer variable. Consequently, what an array 'points to' cannot be changed, and it is impossible to assign a new address to an array name. Array contents may be copied, however, by using the memcpy function, or by accessing the individual elements.Memory management One of the most important functions of a programming language is to provide facilities for managing and the objects that are stored in memory.

This section needs additional citations for. Unsourced material may be challenged and removed.Find sources: – ( July 2014) A number of tools have been developed to help C programmers find and fix statements with undefined behavior or possibly erroneous expressions, with greater rigor than that provided by the compiler. The tool was the first such, leading to many others.Automated source code checking and auditing are beneficial in any language, and for C many such tools exist, such as. A common practice is to use Lint to detect questionable code when a program is first written. Once a program passes Lint, it is then compiled using the C compiler. Also, many compilers can optionally warn about syntactically valid constructs that are likely to actually be errors. Is a proprietary set of guidelines to avoid such questionable code, developed for embedded systems.There are also compilers, libraries, and operating system level mechanisms for performing actions that are not a standard part of C, such as for arrays, detection of, tracking, and.Tools such as or and linking with libraries containing special versions of the can help uncover runtime errors in memory usage.Uses.

The graph, showing a comparison of the popularity of various programming languagesC is widely used for in implementing and applications, because C code, when written for portability, can be used for most purposes, yet when needed, system-specific code can be used to access specific hardware addresses and to perform to match externally imposed interface requirements, with a low demand on system resources.C can also be used for website programming using as a 'gateway' for information between the Web application, the server, and the browser. C is often chosen over because of its speed, stability, and near-universal availability.One consequence of C's wide availability and efficiency is that, libraries and of other programming languages are often implemented in C. The of, and, for example, are all written in C.Because the layer of abstraction is thin and the overhead is low, C enables programmers to create efficient implementations of algorithms and data structures, useful for computationally intense programs. For example, the, the, and are completely or partially written in C.C is sometimes used as an by implementations of other languages. This approach may be used for portability or convenience; by using C as an intermediate language, additional machine-specific code generators are not necessary.

C has some features, such as line-number preprocessor directives and optional superfluous commas at the end of initializer lists, that support compilation of generated code. However, some of C's shortcomings have prompted the development of other specifically designed for use as intermediate languages, such as.C has also been widely used to implement applications. However, such applications can also be written in newer, higher-level languages.Related languages C has both directly and indirectly influenced many later languages such as, and Unix's. The most pervasive influence has been syntactical, all of the languages mentioned combine the statement and (more or less recognizably) expression with type systems, data models and/or large-scale program structures that differ from those of C, sometimes radically.Several C or near-C interpreters exist, including and, which can also be used for scripting.When object-oriented languages became popular, and were two different extensions of C that provided object-oriented capabilities. Both languages were originally implemented as; source code was translated into C, and then compiled with a C compiler.The programming language was devised by as an approach to providing functionality with a C-like syntax.

C adds greater typing strength, scoping, and other tools useful in object-oriented programming, and permits via templates. Nearly a superset of C, C now supports most of C, with.was originally a very 'thin' layer on top of C, and remains a strict superset of C that permits object-oriented programming using a hybrid dynamic/static typing paradigm. Objective-C derives its syntax from both C and: syntax that involves preprocessing, expressions, function declarations, and function calls is inherited from C, while the syntax for object-oriented features was originally taken from Smalltalk.In addition to and, and are nearly supersets of C.See also.Notes. The original example code will compile on most modern compilers that are not in strict standard compliance mode, but it does not fully conform to the requirements of either C89 or C99. In fact, C99 requires that a diagnostic message be produced. The main function actually has two arguments, int argc and char.argv, respectively, which can be used to handle.

The ISO C standard (section 5.1.2.2.1) requires both forms of main to be supported, which is special treatment not afforded to any other function.References. ^; (February 1978). (1st ed.).:.: 'Thompson had made a brief attempt to produce a system coded in an early version of C—before structures—in 1972, but gave up the effort.' .: 'The scheme of type composition adopted by C owes considerable debt to Algol 68, although it did not, perhaps, emerge in a form that Algol's adherents would approve of.' Ring 1.10 documentation. Retrieved 27 June 2019. ^ (PDF).

The Research School of Computer Science at the Australian National University. Archived from (PDF) on 2013-11-06. Retrieved 2013-08-19. 1980s:; Verilog first introduced; Verilog inspired by the C programming language. Archived from on 13 December 2007.

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ACM SIGPLAN Notices. 28 (3): 201–208. ^; (1978). 'Portability of C Programs and the UNIX System'. Bell System Tech. 57 (6): 2021–2048.

(Note: this reference is an OCR scan of the original, and contains an OCR glitch rendering 'IBM 370' as 'IBM 310'.). (1987). (PDF) (Technical report). 139. ^; (March 1988).

(2nd ed.).:. (2002). (PDF) (Report). International Organization for Standardization. Retrieved 2 June 2011.

Andrew Binstock (October 12, 2011). Retrieved September 7, 2013. (PDF). Retrieved 26 July 2011.

Harbison, Samuel P.; (2002). C: A Reference Manual (5th ed.).:. Contains a grammar for C.; (1996). The C Programming Language (2nd ed.). P. 192. Page 3 of the original K&R.; (1996).

The C Programming Language (2nd ed.). Pp. 192, 259. Retrieved 26 June 2009. Schultz, Thomas (2004).

Otsego, MI: PageFree Publishing Inc. Retrieved 10 February 2012. Page 6 of the original K&R. ^ (2013).

21st Century C. Feuer, Alan R.; Gehani, Narain H. (March 1982). 'Comparison of the Programming Languages C and Pascal'. ACM Computing Surveys.

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Pp. 225–230. (11 October 1996). Retrieved 5 August 2012. Summit, Steve. Retrieved March 6, 2013. Summit, Steve.

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Dobb's Sourcebook. U.S.A.: Miller Freeman, Inc. November–December 1995. 1 March 2005. Retrieved 4 January 2010. Gerard), O'Regan, Gerard (Cornelius (2015-09-24).

Pillars of computing: a compendium of select, pivotal technology firms. Lawrence., Rauchwerger (2004). Languages and compilers for parallel computing: 16th international workshop, LCPC 2003, College Station, TX, USA, October 2-4, 2003: revised papers. Springer. (1993).

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The second ACM History of Programming Languages Conference (HOPL-II). Cambridge, MA, USA — April 20–23, 1993:. Retrieved 2014-11-04.Further reading.

Banahan, M.; Brady, D.; Doran, M. (2nd ed.). King, K. (April 2008). C Programming: A Modern Approach (2nd ed.). Murray Hill, New Jersey: AT&T Bell Laboratories. Feuer, Alan R.

The C Puzzle Book (1st, revised printing ed.).External links.

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