Null coalescing operator Wikipedia
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systems programming

However, do note that a shift operand value which is either a negative number or is greater than or equal to the total number of bits in this value results in undefined behavior. For example, when shifting a 32 bit unsigned integer, a shift amount of 32 or higher would be undefined. The precedence table determines the order of binding in chained expressions, when it is not expressly specified by parentheses. «The syntax [i.e., grammar] specifies the precedence of operators in the evaluation of an expression, which is the same as the order of the major subclauses of this subclause, highest precedence first.»

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However, in early versions of C 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 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 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. The for statement has separate initialization, testing, and reinitialization expressions, any or all of which can be omitted.

Since C# 3.0 the syntactic sugar of auto-implemented properties is available, where the accessor and mutator encapsulate operations on a single attribute of a class. Square brackets are used with arrays, both to declare them and to get a value at a given index in one of them. The language is intended for use in developing software components suitable for deployment in distributed environments. Ruby has a null coalescing operator since version 2.3 and calls it both «safe navigation operator» and «lonely operator».

Null coalescing operator

Earlier instances include the Multics system (which was written in PL/I) and Master Control Program for the Burroughs B5000 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 as the basis for several implementations of C on new platforms. While C does not include certain features found in other languages , these can be implemented or emulated, often through the use of external libraries (e.g., the GLib Object System or the Boehm garbage collector). Low-level access to computer memory is possible by converting machine addresses to pointers.

  • While C does not include certain features found in other languages , these can be implemented or emulated, often through the use of external libraries (e.g., the GLib Object System or the Boehm garbage collector).
  • Dereferencing a null pointer value is undefined, often resulting in a segmentation fault.
  • The only implicit conversions by default are those that are considered safe, such as widening of integers.

C has both directly and indirectly influenced many later languages such as C++ and Java. The most pervasive influence has been syntactical; all of the languages mentioned combine the statement and expression syntax of C with type systems, data models or large-scale program structures that differ from those of C, sometimes radically. C lacks standard support for exception handling and only offers return codes for error checking. The setjmp and longjmp standard library functions have been used to implement a try-catch mechanism via macros.

Market Cap is calculated by multiplying the number of shares outstanding by the stock’s price. To calculate, start with total shares outstanding and subtract the number of restricted shares. Restricted stock typically is that issued to company insiders with limits on when it may be traded.Dividend YieldA company’s dividend expressed as a percentage of its current stock price.


The only implicit conversions by default are those that are considered safe, such as widening of integers. This is enforced at compile-time, during JIT, and, in some cases, at runtime. No implicit conversions occur between Booleans and integers, nor between enumeration members and integers . Any user-defined conversion must be explicitly marked as explicit or implicit, unlike C++ copy constructors and conversion operators, which are both implicit by default. In earlier versions, it could be used via a Babel plugin, and in TypeScript.


The C programming language uses libraries as its primary method of extension. In C, a library is a set of functions contained within a single «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 order for a program to use a library, it must include the library’s header file, and the library must be linked with the program, which in many cases requires compiler flags (e.g., -lm, shorthand for «link the math library»). One of the aims of the C standardization process was to produce a superset of K&R C, incorporating many of the subsequently introduced unofficial features. The standards committee also included several additional features such as function prototypes (borrowed from C++), void pointers, support for international character sets and locales, and preprocessor enhancements.

C (programming language)

User-defined and compound types are possible.Heterogeneous aggregate data types allow related data elements to be accessed and assigned as a unit. The book introduced the «Hello, World!» program, which prints only the text «hello, world», as an illustration of a minimal working C program. Since then, many texts have followed that convention for introducing a programming language. Unboxing is the operation of converting a value of a reference type into a value of a value type. The C# language does not allow for global variables or functions.

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C has direct control over memory allocation and deallocation, which gives reasonable efficiency and predictable timing to memory-handling operations, without any concerns for sporadic stop-the-world garbage collection events – it has predictable performance. The closing curly brace indicates the end of the code for the main function. According to the C99 specification and newer, the main function, unlike any other function, will implicitly return a value of 0 upon reaching the that terminates the function. (Formerly an explicit return 0; statement was required.) This is interpreted by the run-time system as an exit code indicating successful execution. The first line of the program contains a preprocessing directive, indicated by #include. This causes the compiler to replace that line with the entire text of the stdio.h standard header, which contains declarations for standard input and output functions such as printf and scanf.


The «hello, world» example, which appeared in the first edition of K&R, has become the model for an introductory program in most programming textbooks. The program prints «hello, world» to the standard output, which is usually a terminal or screen display. The basic C execution character set contains the same characters, along with representations for alert, backspace, and carriage return.

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The first edition, published February 22, 1978, was the first widely available book on the C programming language. Its version of C is sometimes termed K&R C (after the book’s authors), often to distinguish this early version from the later version of C standardized as ANSI C. The C# specification details a minimum set of types and class libraries that the compiler expects to have available. In practice, C# is most often used with some implementation of the Common Language Infrastructure , which is standardized as ECMA-335 Common Language Infrastructure . Source generators, a feature of the Roslyn C# compiler, enable compile time metaprogramming. During the compilation process, developers can inspect the code being compiled with the compiler’s API and pass additional generated C# source code to be compiled.

Instead, he created a cut-down version of the recently developed BCPL systems programming language. The official description of BCPL was not available at the time and Thompson modified the syntax to be less wordy, and similar to a simplified ALGOL known as SMALGOL. Like BCPL, B had a bootstrapping compiler to facilitate porting to new machines. However, few utilities were ultimately written in B because it was too slow, and could not take advantage of PDP-11 features such as byte addressability. When object-oriented programming languages became popular, C++ and Objective-C were two different extensions of C that provided object-oriented capabilities. Both languages were originally implemented as source-to-source compilers; source code was translated into C, and then compiled with a C compiler.

C is the twelfth most frequently used letter in the English language , with a frequency of about 2.8% in words. On the continent, meanwhile, a similar phonetic change before the same two vowels had also been going on in almost all modern romance languages . Other alphabets have letters homoglyphic to ‘c’ but not analogous in use and derivation, like the Cyrillic letter Es (С, с) which derives from the lunate sigma, named due to its resemblance to the crescent moon. The most significant bit of the first number is 1 and that of the second number is also 1 so the most significant bit of the result is 1; in the second most significant bit, the bit of second number is zero, so we have the result as 0.

A consequence of C’s wide availability and efficiency is that compilers, libraries and interpreters of other programming languages are often implemented in C. For example, the reference implementations of Python, Perl, Ruby, and PHP are written in C. Dereferencing a null pointer value is undefined, often resulting in a segmentation fault. Null pointer values are useful for indicating special cases such as no «next» pointer in the final node of a linked list, 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.

The more recent C99 also allows a form of variable-length arrays. However, it is also possible to allocate a block of memory at run-time, using the standard library’s malloc function, and treat it as an array. C# is a general-purpose high-level programming language supporting multiple paradigms. C# encompasses static typing, strong typing, lexically scoped, imperative, declarative, functional, generic, object-oriented (class-based), and component-oriented programming disciplines. However, logical operators treat each operand as having only one value, either true or false, rather than treating each bit of an operand as an independent value. Logical operators consider zero false and any nonzero value true.

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Another difference is that logical operators perform short-circuit evaluation. In the C programming language, operations can be performed on a bit level using bitwise operators. This is a list of operators in the C and C++ programming languages. All the operators listed exist in C++; the column «Included in C», states whether an operator is also present in C. Unless otherwise specified, static objects contain zero or null pointer 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 .

If the program attempts to access an uninitialized value, the results are undefined. Many modern compilers try to detect and warn about this problem, but both false positives and false negatives can occur. Since arrays are always accessed via pointers, array accesses are typically not checked against the underlying array size, although some compilers may provide bounds checking as an option. Array bounds violations are therefore possible and can lead to various repercussions, including illegal memory accesses, corruption of data, buffer overruns, and run-time exceptions. Using LINQ in C# brings advantages like Intellisense support, strong filtering capabilities, type safety with compile error checking ability, and consistency for querying data over a variety of sources.


The language previously included a reserved word called entry, but this was seldom implemented, and has now[when? Many of these had already been implemented as extensions in several C compilers. C89 is supported by current C compilers, and most modern C code is based on it. Any program written only in Standard C and without any hardware-dependent assumptions will run correctly on any platform with a conforming C implementation, within its resource limits. These three approaches are appropriate in different situations and have various trade-offs. For example, static memory allocation has little allocation overhead, automatic allocation may involve slightly more overhead, and dynamic memory allocation can potentially have a great deal of overhead for both allocation and deallocation.

  • C has been standardized by ANSI since and by the International Organization for Standardization .
  • Bitwise operations are contrasted by byte-level operations which characterize the bitwise operators’ logical counterparts, the AND, OR, NOT operators.
  • C# 3.0 expanded support for functional programming with the introduction of a lightweight syntax for lambda expressions, extension methods , and a list comprehension syntax in the form of a «query comprehension» language.

During the late 1970s and 1980s, c# development outsourcings of C were implemented for a wide variety of mainframe computers, minicomputers, and microcomputers, including the IBM PC, as its popularity began to increase significantly. The int type specifiers which are commented out could be omitted in K&R C, but are required in later standards. Complex functionality such as I/O, string manipulation, and mathematical functions are consistently delegated to library routines. Functions may not be defined within the lexical scope of other functions. The Godot game engine has implemented an optional C# module thanks to a donation of $24,000 from Microsoft.

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