C# Read User Input and Put in Array in Console

General-purpose programming linguistic communication

C
Major implementations
The C Programming Language ^[1] (often referred to as K&R), the seminal book on C
Paradigm	Multi-epitome: imperative (procedural), structured
Designed past	Dennis Ritchie
Developer	Dennis Ritchie & Bell Labs (creators); ANSI X3J11 (ANSI C); ISO/IEC JTC1/SC22/WG14 (ISO C)
First appeared	1972; 50 years agone (1972) ^[two]

Stable release	C17 / June 2018; iii years ago (2018-06)
Preview release	C2x (N2731) / October xviii, 2021; iv months ago (2021-ten-xviii) ^[3]

Typing discipline	Static, weak, manifest, nominal
OS	Cross-platform
Filename extensions	.c, .h
Website	world wide web.iso.org/standard/74528.html www.open-std.org/jtc1/sc22/wg14/
pcc, GCC, Clang, Intel C, C++Builder, Microsoft Visual C++, Watcom C
Dialects
Cyclone, Unified Parallel C, Split-C, Cilk, C*
Influenced by
B (BCPL, CPL), ALGOL 68,^[4] associates, PL/I, FORTRAN
Influenced
Numerous: AMPL, AWK, csh, C++, C--, C#, Objective-C, D, Go, Java, JavaScript, JS++, Julia, Limbo, LPC, Perl, PHP, Pike, Processing, Python, Band,^[5]Rust, Seed7, Vala, Verilog (HDL),^[six] Nim, Zig
C Programming at Wikibooks

C (, as in the letter c) is a general-purpose, procedural computer programming language supporting structured programming, lexical variable scope, and recursion, with a static type system. By design, C provides constructs that map efficiently to typical machine instructions. It has establish lasting employ in applications previously coded in assembly language. Such applications include operating systems and diverse application software for computer architectures that range from supercomputers to PLCs and embedded systems.

A successor to the programming language B, C was originally developed at Bell Labs by Dennis Ritchie between 1972 and 1973 to construct utilities running on Unix. It was practical to re-implementing the kernel of the Unix operating system.^[vii] During the 1980s, C gradually gained popularity. It has become one of the about widely used programming languages,^[viii] ^[nine] with C compilers from various vendors bachelor for the majority of existing computer architectures and operating systems. C has been standardized by ANSI since 1989 (ANSI C) and by the International Organization for Standardization (ISO).

C is an imperative procedural linguistic communication. It was designed to be compiled to provide low-level access to memory and language constructs that map efficiently to machine instructions, all with minimal runtime support. Despite its low-level capabilities, the language was designed to encourage cross-platform programming. A standards-compliant C program written with portability in listen can exist compiled for a broad variety of computer platforms and operating systems with few changes to its source code.^[x]

Since 2000, C has consistently ranked amongst the top 2 languages in the TIOBE index, a measure out of the popularity of programming languages.^[11]

Overview [edit]

Similar most procedural languages in the ALGOL tradition, C has facilities for structured programming and allows lexical variable scope and recursion. Its static type organization prevents unintended operations. In C, all executable code is independent inside subroutines (also called "functions", though not strictly in the sense of functional programming). Role parameters are always passed by value (except arrays). Pass-past-reference is simulated in C by explicitly passing pointer values. C program source text is free-format, using the semicolon as a statement terminator and curly braces for group blocks of statements.

The C language also exhibits the following characteristics:

The language has a small, fixed number of keywords, including a total set of control flow primitives: if/else, for, do/while, while, and switch. User-divers names are not distinguished from keywords by any kind of sigil.
It has a large number of arithmetic, bitwise, and logic operators: +,+=,++,&,||, etc.
More than than one consignment may be performed in a single argument.
Functions:
- Function render values tin can exist ignored, when not needed.
- Part and information pointers allow advertisement hoc run-fourth dimension polymorphism.
- Functions may not be defined within the lexical telescopic of other functions.
Data typing is static, but weakly enforced; all data has a type, but implicit conversions are possible.
Declaration syntax mimics usage context. C has no "ascertain" keyword; instead, a statement kickoff with the proper name of a blazon is taken as a annunciation. At that place is no "office" keyword; instead, a function is indicated by the presence of a parenthesized argument list.
User-defined (typedef) and compound types are possible.
- Heterogeneous aggregate data types (struct) allow related information elements to be accessed and assigned as a unit of measurement.
- Matrimony is a structure with overlapping members; only the final fellow member stored is valid.
- Array indexing is a secondary note, defined in terms of pointer arithmetic. Dissimilar structs, arrays are not fantabulous objects: they cannot be assigned or compared using single born operators. There is no "array" keyword in use or definition; instead, square brackets indicate arrays syntactically, for case calendar month[11].
- Enumerated types are possible with the enum keyword. They are freely interconvertible with integers.
- Strings are non a distinct data type, but are conventionally implemented as cipher-terminated character arrays.
Low-level admission to computer memory is possible past converting machine addresses to typed pointers.
Procedures (subroutines not returning values) are a special example of role, with an untyped return type void.
A preprocessor performs macro definition, source lawmaking file inclusion, and provisional compilation.
There is a bones 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.

While C does not include certain features found in other languages (such equally object orientation and garbage drove), these can be implemented or emulated, often through the apply of external libraries (e.1000., the GLib Object System or the Boehm garbage collector).

Relations to other languages [edit]

Many afterwards languages have borrowed straight or indirectly from C, including C++, C#, Unix'southward C shell, D, Go, Java, JavaScript (including transpilers), Julia, Limbo, LPC, Objective-C, Perl, PHP, Python, Ruby, Rust, Swift, Verilog and SystemVerilog (hardware clarification languages).^{[half dozen]} These languages accept drawn many of their control structures and other basic features from C. Near of them (Python existence a dramatic exception) also express highly similar syntax to C, and they tend to combine the recognizable expression and statement syntax of C with underlying type systems, data models, and semantics that can exist radically different.

History [edit]

Early on developments [edit]

Timeline of linguistic communication development
Year	C Standard^[10]
1972	Birth
1978	M&R C
1989/1990	ANSI C and ISO C
1999	C99
2011	C11
2017	C17
TBD	C2x

The origin of C is closely tied to the development of the Unix operating arrangement, originally implemented in associates language on a PDP-7 by Dennis Ritchie and Ken Thompson, incorporating several ideas from colleagues. Eventually, they decided to port the operating system to a PDP-11. The original PDP-xi version of Unix was also developed in assembly linguistic communication.^[seven]

Thompson desired a programming language to make utilities for the new platform. At showtime, he tried to brand a Fortran compiler, simply soon gave up the idea. Instead, he created a cut-down version of the recently adult BCPL systems programming linguistic communication. The official description of BCPL was non available at the time,^[12] and Thompson modified the syntax to be less wordy, producing the similar but somewhat simpler B.^[7] Withal, few utilities were ultimately written in B because it was too wearisome, and B could not take reward of PDP-11 features such every bit byte addressability.

In 1972, Ritchie started to improve B, most notably calculation data typing for variables, which resulted in creating a new language C.^[13] The C compiler and some utilities made with it were included in Version 2 Unix.^[14]

At Version 4 Unix, released in November 1973, the Unix kernel was extensively re-implemented in C.^[seven] By this time, the C language had caused some powerful features such as struct types.

The preprocessor was introduced around 1973 at the urging of Alan Snyder and also in recognition of the usefulness of the file-inclusion mechanisms available in BCPL and PL/I. Its original version provided only included files and uncomplicated string replacements: #include and #define of parameterless macros. Before long subsequently that, it was extended, mostly by Mike Lesk and then past John Reiser, to contain macros with arguments and conditional compilation.^[7]

Unix was one of the beginning operating organisation kernels implemented in a language other than assembly. Earlier instances include the Multics organization (which was written in PL/I) and Main Control Program (MCP) for the Burroughs B5000 (which was written in ALGOL) in 1961. In around 1977, Ritchie and Stephen C. Johnson made further changes to the language to facilitate portability of the Unix operating system. Johnson's Portable C Compiler served equally the basis for several implementations of C on new platforms.^[13]

1000&R C [edit]

In 1978, Brian Kernighan and Dennis Ritchie published the kickoff edition of The C Programming Language.^[1] This book, known to C programmers equally Thousand&R, served for many years every bit an breezy specification of the language. The version of C that information technology describes is commonly referred to as "Thou&R C". As this was released in 1978, information technology is also referred to every bit C78.^[15] The 2d edition of the book^[16] covers the afterward ANSI C standard, described beneath.

1000&R introduced several linguistic communication features:

Standard I/O library
long int data type
unsigned int data type
Compound assignment operators of the form =op (such as =-) were changed to the form op= (that is, -=) to remove the semantic ambiguity created by constructs such as i=-x, which had been interpreted as i =- 10 (decrement i by 10) instead of the possibly intended i = -10 (let i exist −x).

Fifty-fifty later the publication of the 1989 ANSI standard, for many years M&R C was still considered the "lowest common denominator" to which C programmers restricted themselves when maximum portability was desired, since many older compilers were still in use, and because carefully written Yard&R C lawmaking tin can be legal Standard C besides.

In early versions of C, merely functions that return types other than int must be declared if used before the function definition; functions used without prior declaration were presumed to return type int.

For example:

                        long                                    some_function            ();                        /* int */                                    other_function            ();                        /* int */                                    calling_function            ()                        {                                                long                                    test1            ;                                                register                                    /* int */                                    test2            ;                                                test1                                    =                                    some_function            ();                                                if                                    (            test1                                    >                                    one            )                                                test2                                    =                                    0            ;                                                else                                                test2                                    =                                    other_function            ();                                                render                                    test2            ;                        }

The int type specifiers which are commented out could be omitted in K&R C, but are required in subsequently standards.

Since Thou&R office declarations did non include any data about function arguments, function parameter type checks were not performed, although some compilers would event a warning bulletin if a local role was called with the wrong number of arguments, or if multiple calls to an external function used dissimilar numbers or types of arguments. Separate tools such equally Unix'due south lint utility were adult that (amidst other things) could check for consistency of function use across multiple source files.

In the years following the publication of K&R C, several features were added to the language, supported past compilers from AT&T (in particular PCC^[17]) and another vendors. These included:

void functions (i.e., functions with no render value)
functions returning struct or union types (rather than pointers)
assignment for struct data types
enumerated types

The large number of extensions and lack of agreement on a standard library, together with the language popularity and the fact that non even the Unix compilers precisely implemented the Grand&R specification, led to the necessity of standardization.

ANSI C and ISO C [edit]

During the late 1970s and 1980s, versions of C were implemented for a wide multifariousness of mainframe computers, minicomputers, and microcomputers, including the IBM PC, every bit its popularity began to increase significantly.

In 1983, the American National Standards Plant (ANSI) formed a committee, X3J11, to establish a standard specification of C. X3J11 based the C standard on the Unix implementation; withal, the non-portable portion of the Unix C library was handed off to the IEEE working group 1003 to get the footing for the 1988 POSIX standard. In 1989, the C standard was ratified as ANSI X3.159-1989 "Programming Language C". This version of the language is oft referred to as ANSI C, Standard C, or sometimes C89.

In 1990, the ANSI C standard (with formatting changes) was adopted by the International Organization for Standardization (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, just defers to the international C standard, maintained past the working grouping ISO/IEC JTC1/SC22/WG14. National adoption of an update to the international standard typically occurs within a year of ISO publication.

Ane of the aims of the C standardization procedure was to produce a superset of M&R C, incorporating many of the afterwards introduced unofficial features. The standards committee also included several boosted features such as part prototypes (borrowed from C++), void pointers, support for international grapheme sets and locales, and preprocessor enhancements. Although the syntax for parameter declarations was augmented to include the fashion used in C++, the M&R interface continued to be permitted, for compatibility with existing source lawmaking.

C89 is supported past current C compilers, and most modernistic C code is based on it. Any plan written merely in Standard C and without any hardware-dependent assumptions will run correctly on any platform with a befitting C implementation, inside its resource limits. Without such precautions, programs may compile only on a certain platform or with a particular compiler, due, for example, to the apply of non-standard libraries, such equally GUI libraries, or to a reliance on compiler- or platform-specific attributes such equally the exact size of data types and byte endianness.

In cases where lawmaking must be compilable past either standard-conforming or K&R C-based compilers, the __STDC__ macro can exist used to split the code into Standard and Thou&R sections to preclude the use on a 1000&R C-based compiler of features bachelor simply in Standard C.

Later the ANSI/ISO standardization procedure, the C linguistic communication specification remained relatively static for several years. In 1995, Normative Amendment 1 to the 1990 C standard (ISO/IEC 9899/AMD1:1995, known informally as C95) was published, to correct some details and to add more than extensive back up for international character sets.^[eighteen]

C99 [edit]

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 equally "C99". It has since been amended three times by Technical Corrigenda.^[19]

C99 introduced several new features, including inline functions, several new information types (including long long int and a circuitous type to represent complex numbers), variable-length arrays and flexible array members, improved back up for IEEE 754 floating point, support for variadic macros (macros of variable arity), and back up for one-line comments starting time with //, equally in BCPL or C++. Many of these had already been implemented as extensions in several C compilers.

C99 is for the most function backward uniform with C90, simply is stricter in some ways; in detail, a declaration that lacks a type specifier no longer has int implicitly causeless. A standard macro __STDC_VERSION__ is defined with value 199901L to bespeak that C99 support is bachelor. GCC, Solaris Studio, and other C compilers now support many or all of the new features of C99. The C compiler in Microsoft Visual C++, however, implements the C89 standard and those parts of C99 that are required for compatibility with C++eleven.^[20] ^{[ needs update ]}

In addition, support for Unicode identifiers (variable / part names) in the grade of escaped characters (due east.m. \U0001f431) is now required. Back up for raw Unicode names is optional.

C11 [edit]

In 2007, work began on another revision of the C standard, informally chosen "C1X" until its official publication on 2011-12-08. The C standards commission 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 __STDC_VERSION__ is defined as 201112L to bespeak that C11 support is available.

C17 [edit]

Published in June 2018, C17 is the current standard for the C programming language. It introduces no new language features, merely technical corrections, and clarifications to defects in C11. The standard macro __STDC_VERSION__ is defined every bit 201710L.

C2x [edit]

C2x is an informal name for the next (after C17) major C language standard revision. It is expected to exist voted on in 2023 and would therefore be called C23.^[21] ^{[ better source needed ]}

Embedded C [edit]

Historically, embedded C programming requires nonstandard extensions to the C linguistic communication in order to support exotic features such as stock-still-point arithmetic, multiple distinct retention banks, and bones I/O operations.

In 2008, the C Standards Committee published a technical report extending the C language^[22] to accost these issues by providing a common standard for all implementations to adhere to. It includes a number of features non available in normal C, such every bit stock-still-point arithmetic, named address spaces, and bones I/O hardware addressing.

Syntax [edit]

C has a formal grammar specified by the C standard.^[23] Line endings are mostly not meaning in C; however, line boundaries exercise have significance during the preprocessing phase. Comments may appear either between the delimiters /* and */, or (since C99) post-obit // until the end of the line. Comments delimited past /* and */ do not nest, and these sequences of characters are not interpreted equally comment delimiters if they appear inside string or character literals.^[24]

C source files contain declarations and role definitions. Role definitions, in plow, 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 past the variable proper name. Keywords such as char and int specify built-in types. Sections of code are enclosed in braces ({ and }, sometimes chosen "curly brackets") to limit the scope of declarations and to act as a single statement for command structures.

As an imperative language, C uses statements to specify deportment. The most mutual argument is an expression statement, consisting of an expression to be evaluated, followed past a semicolon; as a side upshot of the evaluation, functions may be chosen 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] provisional execution and by do … while, while, and for iterative execution (looping). The for statement has separate initialization, testing, and reinitialization expressions, whatever or all of which can exist omitted. interruption and go along can exist used to leave the innermost enclosing loop statement or skip to its reinitialization. There is too a non-structured goto statement which branches direct to the designated characterization within the function. switch selects a example to exist executed based on the value of an integer expression.

Expressions can use a variety of built-in operators and may comprise function calls. The order in which arguments to functions and operands to about operators are evaluated is unspecified. The evaluations may fifty-fifty exist interleaved. Still, 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 render from each function phone call. Sequence points as well occur during evaluation of expressions containing certain operators (&&, ||, ?: and the comma operator). This permits a loftier degree of object code optimization by the compiler, but requires C programmers to take more intendance 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 whatever other language, has its blemishes. Some of the operators have the wrong precedence; some parts of the syntax could be better."^[25] The C standard did not effort to correct many of these blemishes, considering of the impact of such changes on already existing software.

Grapheme set [edit]

The bones C source graphic symbol set includes the following characters:

Lowercase and uppercase letters of ISO Basic Latin Alphabet: a–z A–Z
Decimal digits: 0–nine
Graphic characters: ! " # % & ' ( ) * + , - . / : ; < = > ? [ \ ] ^ _ { | } ~
Whitespace characters: space, horizontal tab, vertical tab, form feed, newline

Newline indicates the stop of a text line; it need non 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 characteristic is not withal widely implemented.

The bones C execution grapheme fix contains the same characters, along with representations for alert, backspace, and wagon return. Run-time support for extended graphic symbol sets has increased with each revision of the C standard.

Reserved words [edit]

C89 has 32 reserved words, also known as keywords, which are the words that cannot be used for whatever purposes other than those for which they are predefined:

auto
intermission
example
char
const
continue
default
do
double
else
enum
extern
float
for
goto
if
int
long
register
return
short
signed
sizeof
static
struct
switch
typedef
wedlock
unsigned
void
volatile
while

C99 reserved five more than words:

_Bool
_Complex
_Imaginary
inline
restrict

C11 reserved seven more words:^[26]

_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 course were previously reserved past the C standard for utilise but by implementations. Since existing programme source lawmaking should non take been using these identifiers, it would not be afflicted when C implementations started supporting these extensions to the programming language. Some standard headers practise define more convenient synonyms for underscored identifiers. The language previously included a reserved give-and-take chosen entry, but this was seldom implemented, and has now been removed every bit a reserved word.^[27]

Operators [edit]

C supports a rich set of operators, which are symbols used inside an expression to specify the manipulations to exist 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: ( )
increase 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, post-obit the precedent of Fortran and PL/I, just different ALGOL and its derivatives. C uses the operator == to test for equality. The similarity between these two operators (assignment and equality) may upshot in the accidental employ of one in place of the other, and in many cases, the mistake does non produce an error message (although some compilers produce warnings). For example, the conditional expression if (a == b + 1) might mistakenly exist written equally if (a = b + one), which volition be evaluated as true if a is not cipher after the assignment.^[28]

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 equally x & 1 == 0, which must be written as (x & 1) == 0 if that is the coder'due south intent.^[29]

"Hullo, world" example [edit]

The "hullo, earth" example, which appeared in the first edition of Yard&R, has become the model for an introductory program in most programming textbooks. The program prints "hi, world" to the standard output, which is unremarkably a terminal or screen display.

The original version was:^[30]

                        main            ()                        {                                                printf            (            "hello, world            \n            "            );                        }

A standard-conforming "hello, globe" program is:^[a]

                        #include                                    <stdio.h>                        int                                    main            (            void            )                        {                                                printf            (            "hello, earth            \n            "            );                        }

The kickoff line of the program contains a preprocessing directive, indicated by #include. This causes the compiler to replace that line with the unabridged text of the stdio.h standard header, which contains declarations for standard input and output functions such as printf and scanf. The angle brackets surrounding stdio.h indicate that stdio.h is located using a search strategy that prefers headers provided with the compiler to other headers having the same name, as opposed to double quotes which typically include local or project-specific header files.

The next line indicates that a function named main is being divers. The chief office serves a special purpose in C programs; the run-fourth dimension environs calls the main function to brainstorm program execution. The type specifier int indicates that the value that is returned to the invoker (in this case the run-time environment) equally a result of evaluating the master part, is an integer. The keyword void equally a parameter list indicates that this office takes no arguments.^[b]

The opening curly brace indicates the beginning of the definition of the main office.

The next line calls (diverts execution to) a office named printf, which in this case is supplied from a system library. In this call, the printf function is passed (provided with) a single argument, the accost of the first character in the string literal "how-do-you-do, world\northward". The string literal is an unnamed array with elements of type char, ready automatically by the compiler with a final 0-valued graphic symbol to marker the end of the array (printf needs to know this). The \n is an escape sequence that C translates to a newline grapheme, which on output signifies the stop of the current line. The render value of the printf part is of blazon int, but it is silently discarded since information technology is not used. (A more than careful program might examination the render value to determine whether or not the printf function succeeded.) The semicolon ; terminates the statement.

The closing curly brace indicates the end of the code for the chief part. Co-ordinate to the C99 specification and newer, the principal office, unlike any other office, will implicitly render a value of 0 upon reaching the } that terminates the part. (Formerly an explicit render 0; argument was required.) This is interpreted by the run-time system equally an exit code indicating successful execution.^[31]

Data types [edit]

The type organization in C is static and weakly typed, which makes it similar to the blazon organization of ALGOL descendants such as Pascal.^[32] There are congenital-in types for integers of various sizes, both signed and unsigned, floating-point numbers, and enumerated types (enum). Integer type char is often used for single-byte characters. C99 added a boolean datatype. At that place are also derived types including arrays, pointers, records (struct), and unions (union).

C is oft used in low-level systems programming where escapes from the type arrangement may exist necessary. The compiler attempts to ensure type correctness of most expressions, merely the programmer can override the checks in diverse ways, either past using a type cast 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 another way.

Some find C's declaration syntax unintuitive, particularly for office pointers. (Ritchie's idea was to declare identifiers in contexts resembling their utilise: "announcement reflects use".)^[33]

C'southward usual arithmetic conversions allow for efficient code to be generated, only can sometimes produce unexpected results. For case, 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 [edit]

C supports the utilize of pointers, a type of reference that records the address or location of an object or function in memory. Pointers can be dereferenced to access data stored at the accost pointed to, or to invoke a pointed-to function. Pointers tin can be manipulated using assignment or pointer arithmetic. The run-time representation of a pointer value is typically a raw retentivity address (perhaps augmented by an offset-within-word field), just since a pointer's blazon includes the type of the matter pointed to, expressions including pointers can be type-checked at compile fourth dimension. Pointer arithmetics is automatically scaled by the size of the pointed-to data type. Pointers are used for many purposes in C. Text strings are normally manipulated using pointers into arrays of characters. Dynamic retentivity allotment is performed using pointers. Many data types, such equally trees, are ordinarily implemented as dynamically allocated struct objects linked together using pointers. Pointers to functions are useful for passing functions as arguments to higher-order functions (such as qsort or bsearch) or every bit callbacks to be invoked past event handlers.^[31]

A nothing arrow value explicitly points to no valid location. Dereferencing a nix pointer value is undefined, often resulting in a division fault. Nix pointer values are useful for indicating special cases such as no "next" pointer in the final node of a linked list, or as an mistake indication from functions returning pointers. In appropriate contexts in source code, such equally for assigning to a pointer variable, a aught pointer constant can be written equally 0, with or without explicit casting to a pointer type, or equally the NULL macro divers past several standard headers. In conditional contexts, goose egg arrow values evaluate to false, while all other pointer values evaluate to true.

Void pointers (void *) indicate to objects of unspecified blazon, and tin therefore be used as "generic" data pointers. Since the size and blazon 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.^[31]

Careless use of pointers is potentially dangerous. Because they are typically unchecked, a arrow variable can exist made to point to any capricious location, which can cause undesirable furnishings. Although properly used pointers bespeak to safety places, they tin be fabricated to betoken to unsafe places by using invalid pointer arithmetic; the objects they point to may go along to be used later deallocation (dangling pointers); they may be used without having been initialized (wild pointers); or they may be straight assigned an unsafe value using a cast, wedlock, 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 issues by using more restrictive reference types.

Arrays [edit]

Array types in C are traditionally of a fixed, static size specified at compile time. The more contempo C99 standard also allows a course of variable-length arrays. However, information technology is also possible to allocate a block of memory (of arbitrary size) at run-fourth dimension, using the standard library's malloc office, and treat it as an assortment.

Since arrays are always accessed (in effect) via pointers, array accesses are typically non checked confronting the underlying array size, although some compilers may provide bounds checking as an option.^[34] ^[35] Array premises violations are therefore possible and tin lead to various repercussions, including illegal memory accesses, corruption of information, buffer overruns, and run-time exceptions.

C does non have a special provision for declaring multi-dimensional arrays, only rather relies on recursion within the blazon system to declare arrays of arrays, which effectively accomplishes the same thing. The index values of the resulting "multi-dimensional array" tin be thought of as increasing in row-major order. Multi-dimensional arrays are normally used in numerical algorithms (mainly from applied linear algebra) to shop matrices. The structure of the C array is well suited to this particular task. Even so, in early versions of C the bounds of the array must be known stock-still 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 was to allocate the array with an additional "row vector" of pointers to the columns.) C99 introduced "variable-length arrays" which address this issue.

The following case using modern C (C99 or later) shows allocation of a 2-dimensional array on the heap and the use of multi-dimensional assortment indexing for accesses (which tin can use bounds-checking on many C compilers):

                        int                                    func            (            int                                    N            ,                                    int                                    M            )                        {                                                bladder                                    (            *            p            )[            North            ][            Grand            ]                                    =                                    malloc            (            sizeof                                    *            p            );                                                if                                    (            !            p            )                                                return                                    -1            ;                                                for                                    (            int                                    i                                    =                                    0            ;                                    i                                    <                                    Due north            ;                                    i            ++            )                                                for                                    (            int                                    j                                    =                                    0            ;                                    j                                    <                                    1000            ;                                    j            ++            )                                                (            *            p            )[            i            ][            j            ]                                    =                                    i                                    +                                    j            ;                                                print_array            (            N            ,                                    One thousand            ,                                    p            );                                                free            (            p            );                                                return                                    1            ;                        }

Array–pointer interchangeability [edit]

The subscript notation x[i] (where x designates a pointer) is syntactic sugar for *(ten+i).^[36] Taking advantage of the compiler's knowledge of the pointer type, the address that x + i points to is not the base accost (pointed to by x) incremented by i bytes, but rather is defined to be the base accost incremented past i multiplied by the size of an element that x points to. Thus, ten[i] designates the i+1thursday element of the assortment.

Furthermore, in nigh expression contexts (a notable exception is every bit operand of sizeof), an expression of array type is automatically converted to a pointer to the array's kickoff element. This implies that an array is never copied as a whole when named as an statement to a function, but rather only the address of its outset element is passed. Therefore, although function calls in C apply pass-past-value semantics, arrays are in effect passed past reference.

The total size of an array x can exist determined by applying sizeof to an expression of array type. The size of an chemical element tin can be determined by applying the operator sizeof to any dereferenced element of an array A, every bit in n = sizeof A[0]. This, the number of elements in a declared array A tin can be determined as sizeof A / sizeof A[0]. Annotation, that if only a pointer to the start element is bachelor equally it is oft the case in C code because of the automatic conversion described higher up, the information about the full blazon of the assortment and its length are lost.

Memory management [edit]

One of the nigh important functions of a programming language is to provide facilities for managing retentiveness and the objects that are stored in retentivity. C provides three distinct ways to allocate memory for objects:^[31]

Static retentiveness allocation: space for the object is provided in the binary at compile-time; these objects take an extent (or lifetime) as long as the binary which contains them is loaded into memory.
Automatic memory allocation: temporary objects can exist stored on the stack, and this space is automatically freed and reusable after the cake in which they are declared is exited.
Dynamic memory allocation: blocks of memory of capricious size can be requested at run-time using library functions such as malloc from a region of memory chosen the heap; these blocks persist until subsequently freed for reuse past calling the library function realloc or free

These three approaches are appropriate in dissimilar situations and have various trade-offs. For example, static retention allocation has picayune allocation overhead, automatic allotment may involve slightly more overhead, and dynamic memory allocation can potentially have a great deal of overhead for both allocation and deallocation. The persistent nature of static objects is useful for maintaining state data beyond office calls, automatic allocation is easy to utilise only stack space is typically much more express and transient than either static retention or heap space, and dynamic memory allocation allows convenient allocation of objects whose size is known simply at run-fourth dimension. Nigh C programs make extensive apply of all iii.

Where possible, automatic or static allocation is ordinarily simplest because the storage is managed by the compiler, freeing the developer of the potentially mistake-prone chore of manually allocating and releasing storage. However, many information structures tin alter in size at runtime, and since static allocations (and automatic allocations before C99) must have a fixed size at compile-time, there are many situations in which dynamic allocation is necessary.^[31] Prior to the C99 standard, variable-sized arrays were a common example of this. (See the article on malloc for an example of dynamically allocated arrays.) Unlike automated allocation, which tin fail at run time with uncontrolled consequences, the dynamic allocation functions return an indication (in the class of a null pointer value) when the required storage cannot be allocated. (Static resource allotment that is too big is usually detected past the linker or loader, earlier the program tin can fifty-fifty begin execution.)

Unless otherwise specified, static objects contain zero or null arrow values upon program startup. Automatically and dynamically allocated objects are initialized only if an initial value is explicitly specified; otherwise they initially have indeterminate values (typically, whatsoever flake pattern happens to exist nowadays in the storage, which might non even represent a valid value for that type). If the program attempts to access an uninitialized value, the results are undefined. Many modern compilers try to detect and warn about this problem, just both faux positives and simulated negatives tin can occur.

Heap retentiveness resource allotment has to exist synchronized with its actual usage in any programme to be reused as much as possible. For example, if the only pointer to a heap memory allocation goes out of telescopic or has its value overwritten before it is deallocated explicitly, so that memory cannot be recovered for after reuse and is substantially lost to the plan, a miracle known as a memory leak. Conversely, it is possible for memory to exist freed, just is referenced subsequently, leading to unpredictable results. Typically, the failure symptoms announced in a portion of the programme unrelated to the lawmaking that causes the fault, making information technology difficult to diagnose the failure. Such issues are ameliorated in languages with automated garbage collection.

Libraries [edit]

The C programming language uses libraries as its primary method of extension. In C, a library is a set of functions contained within a unmarried "archive" file. Each library typically has a header file, which contains the prototypes of the functions contained within the library that may be used by a program, and declarations of special data types and macro symbols used with these functions. In club for a programme to use a library, it must include the library's header file, and the library must be linked with the plan, which in many cases requires compiler flags (e.thousand., -lm, shorthand for "link the math library").^[31]

The most common C library is the C standard library, which is specified past the ISO and ANSI C standards and comes with every C implementation (implementations which target limited environments such as embedded systems may provide only a subset of the standard library). This library supports stream input and output, retention allocation, mathematics, character strings, and time values. Several separate standard headers (for instance, stdio.h) specify the interfaces for these and other standard library facilities.

Some other mutual set of C library functions are those used by applications specifically targeted for Unix and Unix-like systems, especially functions which provide an interface to the kernel. These functions are detailed in various standards such as POSIX and the Single UNIX Specification.

Since many programs have been written in C, at that place are a wide variety of other libraries available. Libraries are often written in C because C compilers generate efficient object code; programmers so create interfaces to the library so that the routines can exist used from higher-level languages like Coffee, Perl, and Python.^[31]

File treatment and streams [edit]

File input and output (I/O) is not function of the C linguistic communication itself simply instead is handled by libraries (such every bit the C standard library) and their associated header files (e.one thousand. stdio.h). File treatment is mostly implemented through loftier-level I/O which works through streams. A stream is from this perspective a data flow that is independent of devices, while a file is a concrete device. The high-level I/O is washed through the association of a stream to a file. In the C standard library, a buffer (a memory area or queue) is temporarily used to store data before information technology's sent to the last destination. This reduces the time spent waiting for slower devices, for example a hard bulldoze or solid state drive. Low-level I/O functions are not role of the standard C library^{[ description needed ]} merely are generally part of "blank metallic" programming (programming that's independent of any operating system such equally about embedded programming). With few exceptions, implementations include low-level I/O.

Language tools [edit]

A number of tools have been developed to help C programmers find and fix statements with undefined behavior or peradventure erroneous expressions, with greater rigor than that provided by the compiler. The tool lint was the first such, leading to many others.

Automated source lawmaking checking and auditing are beneficial in whatever language, and for C many such tools exist, such every bit Lint. A common practice is to use Lint to notice questionable code when a program is outset written. One time a program passes Lint, it is then compiled using the C compiler. Also, many compilers tin optionally warn about syntactically valid constructs that are probable to actually be errors. MISRA C is a proprietary set of guidelines to avoid such questionable code, adult for embedded systems.^[37]

There are also compilers, libraries, and operating arrangement level mechanisms for performing actions that are non a standard part of C, such as bounds checking for arrays, detection of buffer overflow, serialization, dynamic retentiveness tracking, and automatic garbage drove.

Tools such equally Purify or Valgrind and linking with libraries containing special versions of the memory allocation functions tin help uncover runtime errors in memory usage.

Uses [edit]

The C Programming Language

C is widely used for systems programming in implementing operating systems and embedded arrangement applications,^[38] because C code, when written for portability, tin can be used for about purposes, still when needed, system-specific lawmaking can exist used to access specific hardware addresses and to perform type punning to match externally imposed interface requirements, with a low run-fourth dimension demand on organization resources.

C tin can be used for website programming using the Common Gateway Interface (CGI) as a "gateway" for data between the Spider web awarding, the server, and the browser.^[39] C is often called over interpreted languages because of its speed, stability, and near-universal availability.^[40]

A consequence of C's wide availability and efficiency is that compilers, libraries and interpreters of other programming languages are oft implemented in C. For example, the reference implementations of Python, Perl, Ruby, and PHP are written in C.

C enables programmers to create efficient implementations of algorithms and data structures, because the layer of brainchild from hardware is thin, and its overhead is depression, an important criterion for computationally intensive programs. For instance, the GNU Multiple Precision Arithmetic Library, the GNU Scientific Library, Mathematica, and MATLAB are completely or partially written in C.

C is sometimes used as an intermediate language by implementations of other languages. This approach may be used for portability or convenience; by using C every bit an intermediate language, additional automobile-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 C-based languages specifically designed for use equally intermediate languages, such as C--.

C has also been widely used to implement end-user applications. However, such applications can also exist written in newer, college-level languages.

[edit]

The TIOBE alphabetize graph, showing a comparing of the popularity of various programming languages^[41]

C has both directly and indirectly influenced many afterward languages such as C#, D, Go, Java, JavaScript, Limbo, LPC, Perl, PHP, Python, and Unix's C shell.^[42] The most pervasive influence has been syntactical; all of the languages mentioned combine the argument and (more or less recognizably) expression syntax of C with type systems, data models, and/or large-calibration program structures that differ from those of C, sometimes radically.

Several C or near-C interpreters exist, including Ch and CINT, which can likewise be used for scripting.

When object-oriented programming languages became popular, C++ and Objective-C were ii unlike extensions of C that provided object-oriented capabilities. Both languages were originally implemented as source-to-source compilers; source lawmaking was translated into C, and so compiled with a C compiler.^[43]

The C++ programming language (originally named "C with Classes") was devised by Bjarne Stroustrup as an approach to providing object-oriented functionality with a C-like syntax.^[44] C++ adds greater typing forcefulness, scoping, and other tools useful in object-oriented programming, and permits generic programming via templates. Most a superset of C, C++ now supports nearly of C, with a few exceptions.

Objective-C 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 Smalltalk: 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 improver to C++ and Objective-C, Ch, Cilk, and Unified Parallel C are virtually supersets of C.

See as well [edit]

Compatibility of C and C++
Comparing of Pascal and C
Comparison of programming languages
International Obfuscated C Code Contest
List of C-based programming languages
Listing of C compilers

Notes [edit]

^ The original case code will compile on most modern compilers that are not in strict standard compliance mode, but it does non 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 control line arguments. The ISO C standard (section five.ane.2.ii.one) requires both forms of primary to be supported, which is special treatment not afforded to any other function.

References [edit]

^ ^a ^b Kernighan, Brian W.; Ritchie, Dennis Yard. (February 1978). The C Programming Linguistic communication (1st ed.). Englewood Cliffs, NJ: Prentice Hall. ISBN978-0-13-110163-0.
^ Ritchie (1993): "Thompson had fabricated a cursory attempt to produce a system coded in an early version of C—before structures—in 1972, simply gave up the try."
^ Fruderica (December 13, 2020). "History of C". The cppreference.com. Archived from the original on October 24, 2020. Retrieved October 24, 2020.
^ Ritchie (1993): "The scheme of type composition adopted past C owes considerable debt to Algol 68, although it did not, peradventure, sally in a form that Algol'south adherents would approve of."
^ Ring Team (October 23, 2021). "The Ring programming language and other languages". ring-lang.cyberspace.
^ ^a ^b "Verilog HDL (and C)" (PDF). The Research Schoolhouse of Computer Science at the Australian National University. June 3, 2010. Archived from the original (PDF) on November 6, 2013. Retrieved August 19, 2013. 1980s: ; Verilog outset introduced ; Verilog inspired past the C programming linguistic communication
^ ^a ^b ^c ^d ^{due east} Ritchie (1993)
^ "Programming Language Popularity". 2009. Archived from the original on January xvi, 2009. Retrieved January 16, 2009.
^ "TIOBE Programming Community Index". 2009. Archived from the original on May iv, 2009. Retrieved May 6, 2009.
^ ^a ^b "History of C". en.cppreference.com. Archived from the original on May 29, 2018. Retrieved May 28, 2018.
^ "TIOBE Alphabetize for Oct 2021". Retrieved October 7, 2021.
^ Ritchie, Dennis. "BCPL to B to C". Archived from the original on December 12, 2019. Retrieved September x, 2019.
^ ^a ^b Johnson, S. C.; Ritchie, D. Yard. (1978). "Portability of C Programs and the UNIX System". Bell System Tech. J. 57 (6): 2021–2048. CiteSeerX10.one.one.138.35. doi:10.1002/j.1538-7305.1978.tb02141.10. S2CID 17510065. (Note: The PDF is an OCR scan of the original, and contains a rendering of "IBM 370" as "IBM 310".)
^ McIlroy, G. D. (1987). A Research Unix reader: annotated excerpts from the Programmer's Transmission, 1971–1986 (PDF) (Technical report). CSTR. Bell Labs. p. 10. 139. Archived (PDF) from the original on November 11, 2017. Retrieved February 1, 2015.
^ "C manual pages". FreeBSD Miscellaneous Data Manual (FreeBSD thirteen.0 ed.). May 30, 2011. Archived from the original on January 21, 2021. Retrieved January 15, 2021. [one] Archived January 21, 2021, at the Wayback Automobile
^ Kernighan, Brian W.; Ritchie, Dennis One thousand. (March 1988). The C Programming Linguistic communication (2d ed.). Englewood Cliffs, NJ: Prentice Hall. ISBN978-0-xiii-110362-7.
^ Stroustrup, Bjarne (2002). Sibling rivalry: C and C++ (PDF) (Study). AT&T Labs. Archived (PDF) from the original on August 24, 2014. Retrieved April fourteen, 2014.
^ C Integrity. International Arrangement for Standardization. March thirty, 1995. Archived from the original on July 25, 2018. Retrieved July 24, 2018.
^ "JTC1/SC22/WG14 – C". Home page. ISO/IEC. Archived from the original on February 12, 2018. Retrieved June 2, 2011.
^ Andrew Binstock (October 12, 2011). "Interview with Herb Sutter". Dr. Dobbs. Archived from the original on August 2, 2013. Retrieved September 7, 2013.
^ "Revised C23 Schedule WG 14 N 2759" (PDF). www.open-std.org. Archived (PDF) from the original on June 24, 2021. Retrieved Oct x, 2021.
^ "TR 18037: Embedded C" (PDF). ISO / IEC. Archived (PDF) from the original on February 25, 2021. Retrieved July 26, 2011.
^ Harbison, Samuel P.; Steele, Guy L. (2002). C: A Reference Manual (fifth ed.). Englewood Cliffs, NJ: Prentice Hall. ISBN978-0-13-089592-9. Contains a BNF grammar for C.
^ Kernighan & Ritchie (1996), p. 192.
^ Kernighan & Ritchie (1978), p. 3.
^ "ISO/IEC 9899:201x (ISO C11) Committee Draft" (PDF). Archived (PDF) from the original on December 22, 2017. Retrieved September sixteen, 2011.
^ Kernighan & Ritchie (1996), pp. 192, 259.
^ "10 Common Programming Mistakes in C++". Cs.ucr.edu. Archived from the original on Oct 21, 2008. Retrieved June 26, 2009.
^ Schultz, Thomas (2004). C and the 8051 (third ed.). Otsego, MI: PageFree Publishing Inc. p. 20. ISBN978-1-58961-237-2. Archived from the original on July 29, 2020. Retrieved Feb 10, 2012.
^ Kernighan & Ritchie (1978), p. six.
^ ^a ^b ^c ^d ^e ^f ¹⁰⁰⁰ Klemens, Ben (2013). 21st Century C. O'Reilly Media. ISBN978-1-4493-2714-9.
^ Feuer, Alan R.; Gehani, Narain H. (March 1982). "Comparing of the Programming Languages C and Pascal". ACM Computing Surveys. 14 (1): 73–92. doi:10.1145/356869.356872. S2CID 3136859.
^ Kernighan & Ritchie (1996), p. 122.
^ For example, gcc provides _FORTIFY_SOURCE. "Security Features: Compile Time Buffer Checks (FORTIFY_SOURCE)". fedoraproject.org. Archived from the original on January 7, 2007. Retrieved August five, 2012.
^ เอี่ยมสิริวงศ์, โอภาศ (2016). Programming with C. Bangkok, Thailand: SE-EDUCATION PUBLIC Company LIMITED. pp. 225–230. ISBN978-616-08-2740-iv.
^ Raymond, Eric S. (October xi, 1996). The New Hacker's Dictionary (3rd ed.). MIT Press. p. 432. ISBN978-0-262-68092-ix. Archived from the original on November 12, 2012. Retrieved August 5, 2012.
^ "Man Folio for lint (freebsd Section 1)". unix.com. May 24, 2001. Retrieved July 15, 2014.
^ Dale, Nell B.; Weems, Scrap (2014). Programming and trouble solving with C++ (6th ed.). Burlington, MA: Jones & Bartlett Learning. ISBN978-1449694289. OCLC 894992484.
^ Dr. Dobb's Sourcebook. U.South.A.: Miller Freeman, Inc. November–December 1995.
^ "Using C for CGI Programming". linuxjournal.com. March 1, 2005. Archived from the original on February 13, 2010. Retrieved January four, 2010.
^ McMillan, Robert (August 1, 2013). "Is Coffee Losing Its Mojo?". Wired. Archived from the original on February 15, 2017. Retrieved March 5, 2017.
^ O'Regan, Gerard (September 24, 2015). Pillars of computing : a compendium of select, pivotal engineering science firms. ISBN978-3319214641. OCLC 922324121.
^ Rauchwerger, Lawrence (2004). Languages and compilers for parallel calculating : 16th international workshop, LCPC 2003, Higher Station, TX, The states, October 2-4, 2003 : revised papers. Springer. ISBN978-3540246442. OCLC 57965544.
^ Stroustrup, Bjarne (1993). "A History of C++: 1979−1991" (PDF). Archived (PDF) from the original on February 2, 2019. Retrieved June 9, 2011.

Sources [edit]

Ritchie, Dennis Chiliad. (March 1993). "The Development of the C Language". ACM SIGPLAN Notices. ACM. 28 (iii): 201–208. doi:10.1145/155360.155580.
Ritchie, Dennis Grand. (1993). "The Development of the C Language". The Second ACM SIGPLAN Conference on History of Programming Languages (HOPL-II). ACM. pp. 201–208. doi:10.1145/154766.155580. ISBN0-89791-570-4 . Retrieved November 4, 2014.
Kernighan, Brian W.; Ritchie, Dennis M. (1996). The C Programming Language (second ed.). Prentice Hall. ISBNvii-302-02412-X.

External links [edit]

ISO C Working Grouping official website
- ISO/IEC 9899, publicly available official C documents, including the C99 Rationale
- "C99 with Technical corrigenda TC1, TC2, and TC3 included" (PDF). (three.61 MB)
comp.lang.c Frequently Asked Questions
A History of C, by Dennis Ritchie

rosadofancessid.blogspot.com

Source: https://en.wikipedia.org/wiki/C_(programming_language)