C# Windows Form Application Filter File Upload
In the C programming linguistic communication, data types constitute the semantics and characteristics of storage of data elements. They are expressed in the language syntax in form of declarations for memory locations or variables. Data types also make up one's mind the types of operations or methods of processing of data elements.
The C linguistic communication provides basic arithmetic types, such as integer and real number types, and syntax to build array and compound types. Headers for the C standard library, to be used via include directives, incorporate definitions of support types, that have additional properties, such as providing storage with an exact size, independent of the linguistic communication implementation on specific hardware platforms.[i] [ii]
Bones types [edit]
Primary types [edit]
The C language provides the four basic arithmetic blazon specifiers char, int, float and double, and the modifiers signed, unsigned, short, and long. The following tabular array lists the permissible combinations in specifying a big gear up of storage size-specific declarations.
| Type | Explanation | Minimum size (bits) | Format specifier | Range | Suffix for decimal constants |
|---|---|---|---|---|---|
char | Smallest addressable unit of the car that can contain basic character set. It is an integer blazon. Actual type can be either signed or unsigned. It contains CHAR_BIT $.25.[3] | 8 | %c | CHAR_MIN / CHAR_MAX | north/a |
signed char | Of the aforementioned size equally char, but guaranteed to exist signed. Capable of containing at least the [−127, +127] range.[three] [a] | 8 | %c (or %hhi for numerical output) | SCHAR_MIN / SCHAR_MAX [5] | due north/a |
unsigned char | Of the same size as char, but guaranteed to be unsigned. Contains at least the [0, 255] range.[6] | viii | %c (or %hhu for numerical output) | 0 / UCHAR_MAX | n/a |
short short int signed short signed curt int | Short signed integer type. Capable of containing at least the [−32,767, +32,767] range.[3] [a] | 16 | %hi or %hd | SHRT_MIN / SHRT_MAX | northward/a |
unsigned short unsigned short int | Short unsigned integer blazon. Contains at to the lowest degree the [0, 65,535] range.[three] | sixteen | %hu | 0 / USHRT_MAX | n/a |
int signed signed int | Basic signed integer blazon. Capable of containing at least the [−32,767, +32,767] range.[3] [a] | sixteen | %i or %d | INT_MIN / INT_MAX | none |
unsigned unsigned int | Bones unsigned integer type. Contains at least the [0, 65,535] range.[3] | 16 | %u | 0 / UINT_MAX | u or U |
long long int signed long signed long int | Long signed integer type. Capable of containing at least the [−two,147,483,647, +ii,147,483,647] range.[3] [a] | 32 | %li or %ld | LONG_MIN / LONG_MAX | 50 or L [7] |
unsigned long unsigned long int | Long unsigned integer type. Capable of containing at least the [0, four,294,967,295] range.[3] | 32 | %lu | 0 / ULONG_MAX | both u or U and fifty or Fifty |
long long long long int signed long long signed long long int | Long long signed integer type. Capable of containing at least the [−9,223,372,036,854,775,807, +nine,223,372,036,854,775,807] range.[3] [a] Specified since the C99 version of the standard. | 64 | %lli or %lld | LLONG_MIN / LLONG_MAX | ll or LL |
unsigned long long unsigned long long int | Long long unsigned integer type. Contains at least the [0, +18,446,744,073,709,551,615] range.[3] Specified since the C99 version of the standard. | 64 | %llu | 0 / ULLONG_MAX | both u or U and ll or LL |
float | Real floating-point type, usually referred to equally a unmarried-precision floating-point type. Actual properties unspecified (except minimum limits); yet, on most systems, this is the IEEE 754 unmarried-precision binary floating-signal format (32 bits). This format is required by the optional Annex F "IEC 60559 floating-signal arithmetic". | Converting from text:[b]
| |||
double | Real floating-signal type, usually referred to as a double-precision floating-point type. Actual backdrop unspecified (except minimum limits); however, on well-nigh systems, this is the IEEE 754 double-precision binary floating-point format (64 $.25). This format is required by the optional Annex F "IEC 60559 floating-point arithmetic". |
| |||
long double | Real floating-betoken type, usually mapped to an extended precision floating-point number format. Actual backdrop unspecified. It can be either x86 extended-precision floating-point format (80 bits, but typically 96 bits or 128 bits in retentiveness with padding bytes), the non-IEEE "double-double" (128 bits), IEEE 754 quadruple-precision floating-signal format (128 bits), or the same as double. See the article on long double for details. | %Lf %LF %Lg %LG %Le %LE %La %LA [c] |
- ^ a b c d east The minimal ranges −(iin−1−1) to 2n−1−1 (due east.g. [−127,127]) come from the diverse integer representations immune by the standard (ones' complement, sign-magnitude, two'southward complement).[4] However, most platforms use ii'southward complement, implying a range of the form −2g−1 to 2m−1−i with thou ≥ n for these implementations, eastward.k. [−128,127] (
SCHAR_MIN= −128 andSCHAR_MAX= 127) for an 8-bit signed char. - ^ These format strings also exist for formatting to text, just operate on a double.
- ^ a b Uppercase differs from lowercase in the output. Uppercase specifiers produce values in the uppercase, and lowercase in lower (%A, %Eastward, %F, %G produce such values equally INF, NAN and E (exponent) in uppercase)
The bodily size of the integer types varies by implementation. The standard requires only size relations between the data types and minimum sizes for each data type:
The relation requirements are that the long long is not smaller than long, which is not smaller than int, which is not smaller than brusk. As char's size is always the minimum supported data blazon, no other data types (except bit-fields) tin can exist smaller.
The minimum size for char is 8 $.25, the minimum size for short and int is xvi bits, for long it is 32 $.25 and long long must incorporate at least 64 $.25.
The type int should be the integer blazon that the target processor is most efficiently working with. This allows great flexibility: for case, all types can be 64-bit. However, several different integer width schemes (data models) are popular. Considering the data model defines how different programs communicate, a uniform information model is used inside a given operating arrangement application interface.[eight]
In do, char is usually 8 bits in size and short is commonly 16 bits in size (as are their unsigned counterparts). This holds true for platforms every bit diverse every bit 1990s SunOS 4 Unix, Microsoft MS-DOS, modern Linux, and Microchip MCC18 for embedded viii-bit Movie microcontrollers. POSIX requires char to be exactly 8 $.25 in size.
Various rules in the C standard brand unsigned char the bones type used for arrays suitable to store arbitrary non-scrap-field objects: its lack of padding bits and trap representations, the definition of object representation,[6] and the possibility of aliasing.[9]
The bodily size and behavior of floating-point types also vary past implementation. The only guarantee is that long double is non smaller than double, which is not smaller than float. Ordinarily, the 32-bit and 64-flake IEEE 754 binary floating-betoken formats are used.
The C99 standard includes new real floating-indicate types float_t and double_t, divers in <math.h>. They represent to the types used for the intermediate results of floating-point expressions when FLT_EVAL_METHOD is 0, 1, or 2. These types may be wider than long double.
C99 also added complex types: float _Complex, double _Complex, long double _Complex.
Boolean blazon [edit]
C99 added a boolean (truthful/fake) blazon _Bool. Additionally, the <stdbool.h> header defines bool as a convenient alias for this type, and as well provides macros for true and imitation. _Bool functions similarly to a normal integer type, with one exception: any assignments to a _Bool that are not 0 (false) are stored as ane (truthful). This behavior exists to avoid integer overflows in implicit narrowing conversions. For example, in the following code:
unsigned char b = 256 ; if ( b ) { /* do something */ } Variable b evaluates to imitation if unsigned char has a size of 8 bits. This is because the value 256 does not fit in the information type, which results in the lower eight $.25 of information technology being used, resulting in a zero value. Yet, irresolute the blazon causes the previous lawmaking to behave unremarkably:
_Bool b = 256 ; if ( b ) { /* do something */ } The type _Bool also ensures truthful values ever compare equal to each other:
_Bool a = 1 , b = two ; if ( a == b ) { /* practise something */ } Size and arrow difference types [edit]
The C language specification includes the typedefsouthward size_t and ptrdiff_t to represent memory-related quantities. Their size is defined according to the target processor's arithmetics capabilities, non the retentivity capabilities, such every bit available address infinite. Both of these types are defined in the <stddef.h> header (cstddef in C++).
size_t is an unsigned integer type used to represent the size of whatsoever object (including arrays) in the detail implementation. The operator sizeof yields a value of the type size_t. The maximum size of size_t is provided via SIZE_MAX, a macro constant which is defined in the <stdint.h> header (cstdint header in C++). size_t is guaranteed to exist at least 16 $.25 wide. Additionally, POSIX includes ssize_t, which is a signed integer type of the same width as size_t.
ptrdiff_t is a signed integer type used to represent the difference between pointers. It is guaranteed to be valid only against pointers of the same blazon; subtraction of pointers consisting of different types is implementation-defined.
Interface to the properties of the basic types [edit]
Information about the actual properties, such equally size, of the basic arithmetic types, is provided via macro constants in 2 headers: <limits.h> header (climits header in C++) defines macros for integer types and <float.h> header (cfloat header in C++) defines macros for floating-point types. The actual values depend on the implementation.
Properties of integer types [edit]
-
CHAR_BIT– size of the char type in bits (at least 8 bits) -
SCHAR_MIN,SHRT_MIN,INT_MIN,LONG_MIN,LLONG_MIN(C99) – minimum possible value of signed integer types: signed char, signed short, signed int, signed long, signed long long -
SCHAR_MAX,SHRT_MAX,INT_MAX,LONG_MAX,LLONG_MAX(C99) – maximum possible value of signed integer types: signed char, signed short, signed int, signed long, signed long long -
UCHAR_MAX,USHRT_MAX,UINT_MAX,ULONG_MAX,ULLONG_MAX(C99) – maximum possible value of unsigned integer types: unsigned char, unsigned short, unsigned int, unsigned long, unsigned long long -
CHAR_MIN– minimum possible value of char -
CHAR_MAX– maximum possible value of char -
MB_LEN_MAX– maximum number of bytes in a multibyte character
Backdrop of floating-point types [edit]
-
FLT_MIN,DBL_MIN,LDBL_MIN– minimum normalized positive value of float, double, long double respectively -
FLT_TRUE_MIN,DBL_TRUE_MIN,LDBL_TRUE_MIN(C11) – minimum positive value of bladder, double, long double respectively -
FLT_MAX,DBL_MAX,LDBL_MAX– maximum finite value of float, double, long double, respectively -
FLT_ROUNDS– rounding mode for floating-point operations -
FLT_EVAL_METHOD(C99) – evaluation method of expressions involving different floating-bespeak types -
FLT_RADIX– radix of the exponent in the floating-signal types -
FLT_DIG,DBL_DIG,LDBL_DIG– number of decimal digits that tin be represented without losing precision by bladder, double, long double, respectively -
FLT_EPSILON,DBL_EPSILON,LDBL_EPSILON– deviation between 1.0 and the next representable value of bladder, double, long double, respectively -
FLT_MANT_DIG,DBL_MANT_DIG,LDBL_MANT_DIG– number ofFLT_RADIX-base digits in the floating-point significand for types float, double, long double, respectively -
FLT_MIN_EXP,DBL_MIN_EXP,LDBL_MIN_EXP– minimum negative integer such thatFLT_RADIXraised to a power one less than that number is a normalized float, double, long double, respectively -
FLT_MIN_10_EXP,DBL_MIN_10_EXP,LDBL_MIN_10_EXP– minimum negative integer such that x raised to that power is a normalized bladder, double, long double, respectively -
FLT_MAX_EXP,DBL_MAX_EXP,LDBL_MAX_EXP– maximum positive integer such thatFLT_RADIXraised to a power one less than that number is a normalized float, double, long double, respectively -
FLT_MAX_10_EXP,DBL_MAX_10_EXP,LDBL_MAX_10_EXP– maximum positive integer such that 10 raised to that ability is a normalized bladder, double, long double, respectively -
DECIMAL_DIG(C99) – minimum number of decimal digits such that whatsoever number of the widest supported floating-bespeak type can be represented in decimal with a precision ofDECIMAL_DIGdigits and read back in the original floating-point blazon without changing its value.DECIMAL_DIGis at least 10.
Stock-still-width integer types [edit]
The C99 standard includes definitions of several new integer types to raise the portability of programs.[2] The already available basic integer types were accounted insufficient, because their bodily sizes are implementation defined and may vary beyond different systems. The new types are especially useful in embedded environments where hardware usually supports only several types and that support varies between different environments. All new types are defined in <inttypes.h> header (cinttypes header in C++) and as well are available at <stdint.h> header (cstdint header in C++). The types can be grouped into the following categories:
- Verbal-width integer types that are guaranteed to have the aforementioned number n of $.25 beyond all implementations. Included only if it is available in the implementation.
- Least-width integer types that are guaranteed to be the smallest blazon bachelor in the implementation, that has at to the lowest degree specified number n of bits. Guaranteed to exist specified for at least N=8,16,32,64.
- Fastest integer types that are guaranteed to be the fastest integer blazon available in the implementation, that has at least specified number n of bits. Guaranteed to be specified for at least N=8,xvi,32,64.
- Pointer integer types that are guaranteed to exist able to concord a pointer. Included only if it is available in the implementation.
- Maximum-width integer types that are guaranteed to be the largest integer type in the implementation.
The post-obit tabular array summarizes the types and the interface to acquire the implementation details (n refers to the number of bits):
| Type category | Signed types | Unsigned types | ||||
|---|---|---|---|---|---|---|
| Type | Minimum value | Maximum value | Type | Minimum value | Maximum value | |
| Exact width | intnorthward_t | INTn_MIN | INTnorthward_MAX | uintnorth_t | 0 | UINTn_MAX |
| Least width | int_leastn_t | INT_LEASTnorth_MIN | INT_LEASTdue north_MAX | uint_leastnorth_t | 0 | UINT_LEASTn_MAX |
| Fastest | int_fastn_t | INT_FASTdue north_MIN | INT_FASTn_MAX | uint_fastn_t | 0 | UINT_FASTdue north_MAX |
| Pointer | intptr_t | INTPTR_MIN | INTPTR_MAX | uintptr_t | 0 | UINTPTR_MAX |
| Maximum width | intmax_t | INTMAX_MIN | INTMAX_MAX | uintmax_t | 0 | UINTMAX_MAX |
Printf and scanf format specifiers [edit]
The <inttypes.h> header (cinttypes in C++) provides features that raise the functionality of the types defined in the <stdint.h> header. Information technology defines macros for printf format cord and scanf format string specifiers corresponding to the types defined in <stdint.h> and several functions for working with the intmax_t and uintmax_t types. This header was added in C99.
- Printf format string
The macros are in the format PRI{fmt}{type} . Here {fmt} defines the output formatting and is ane of d (decimal), x (hexadecimal), o (octal), u (unsigned) and i (integer). {type} defines the blazon of the argument and is one of north , FASTn , To the lowest degreen , PTR, MAX, where n corresponds to the number of bits in the argument.
- Scanf format string
The macros are in the format SCN{fmt}{blazon} . Here {fmt} defines the output formatting and is one of d (decimal), x (hexadecimal), o (octal), u (unsigned) and i (integer). {type} defines the blazon of the statement and is 1 of n , FASTn , Leastn , PTR, MAX, where due north corresponds to the number of bits in the statement.
- Functions
![[icon]](https://upload.wikimedia.org/wikipedia/commons/thumb/1/1c/Wiki_letter_w_cropped.svg/20px-Wiki_letter_w_cropped.svg.png){kind=small} | This section needs expansion. You can assistance by adding to it. (October 2011) |
Additional floating-signal types [edit]
Similarly to the fixed-width integer types, ISO/IEC TS 18661 specifies floating-point types for IEEE 754 interchange and extended formats in binary and decimal:
-
_FloatNorthfor binary interchange formats; -
_DecimalNfor decimal interchange formats; -
_FloatN10for binary extended formats; -
_DecimalDue northxfor decimal extended formats.
Structures [edit]
Structures aggregate the storage of multiple data items, of potentially differing information types, into one memory block referenced by a single variable. The post-obit case declares the information type struct altogether which contains the name and birthday of a person. The construction definition is followed by a announcement of the variable John that allocates the needed storage.
struct birthday { char proper name [ 20 ]; int day ; int month ; int year ; }; struct birthday John ; The memory layout of a structure is a language implementation result for each platform, with a few restrictions. The retentiveness accost of the first member must be the aforementioned equally the accost of structure itself. Structures may be initialized or assigned to using chemical compound literals. A function may straight render a structure, although this is oft not efficient at run-time. Since C99, a construction may also end with a flexible array member.
A structure containing a arrow to a structure of its ain type is usually used to build linked data structures:
struct node { int val ; struct node * next ; }; Arrays [edit]
For every type T, except void and function types, in that location be the types "array of N elements of type T". An array is a collection of values, all of the same type, stored contiguously in memory. An array of size N is indexed by integers from 0 up to and including N−1. Here is a brief example:
int cat [ ten ]; // array of 10 elements, each of type int Arrays can be initialized with a compound initializer, simply non assigned. Arrays are passed to functions by passing a arrow to the starting time chemical element. Multidimensional arrays are defined equally "array of array …", and all except the outermost dimension must take compile-time abiding size:
int a [ 10 ][ 8 ]; // array of ten elements, each of type 'array of 8 int elements' Pointers [edit]
Every information type T has a respective type pointer to T . A arrow is a data blazon that contains the address of a storage location of a variable of a particular type. They are declared with the asterisk (*) type declarator following the basic storage blazon and preceding the variable name. Whitespace earlier or after the asterisk is optional.
char * square ; long * circumvolve ; int * oval ; Pointers may also exist declared for pointer data types, thus creating multiple indirect pointers, such as char ** and int ***, including pointers to array types. The latter are less common than an array of pointers, and their syntax may be confusing:
char * pc [ x ]; // array of ten elements of 'arrow to char' char ( * pa )[ 10 ]; // pointer to a x-element array of char The chemical element pc requires ten blocks of retention of the size of pointer to char (unremarkably twoscore or lxxx bytes on common platforms), but element pa is only one pointer (size 4 or 8 bytes), and the data information technology refers to is an array of ten bytes ( sizeof * pa == ten ).
Unions [edit]
A spousal relationship blazon is a special construct that permits access to the same retentivity block by using a choice of differing type descriptions. For instance, a spousal relationship of data types may be declared to permit reading the same data either as an integer, a float, or whatever other user declared type:
union { int i ; float f ; struct { unsigned int u ; double d ; } s ; } u ; The full size of u is the size of u.southward – which happens to exist the sum of the sizes of usau and u.due south.d – since due south is larger than both i and f. When assigning something to u.i, some parts of u.f may be preserved if u.i is smaller than u.f.
Reading from a marriage fellow member is not the same equally casting since the value of the fellow member is non converted, but just read.
Part pointers [edit]
Function pointers let referencing functions with a item signature. For case, to shop the address of the standard function abs in the variable my_int_f:
int ( * my_int_f )( int ) = & abs ; // the & operator can exist omitted, merely makes clear that the "address of" abs is used here Part pointers are invoked past name just similar normal function calls. Function pointers are split from pointers and void pointers.
Type qualifiers [edit]
The aforementioned types tin be characterized farther by blazon qualifiers, yielding a qualified type. As of 2014[update] and C11, there are four type qualifiers in standard C: const (C89), volatile (C89), restrict (C99) and _Atomic (C11) – the latter has a private proper name to avoid clashing with user names,[10] but the more ordinary name atomic can be used if the <stdatomic.h> header is included. Of these, const is by far the best-known and most used, appearing in the standard library and encountered in any pregnant employ of the C language, which must satisfy const-correctness. The other qualifiers are used for depression-level programming, and while widely used there, are rarely used by typical programmers.[ commendation needed ]
See also [edit]
- C syntax
- Uninitialized variable
- Integer (computer science)
References [edit]
- ^ Barr, Michael (2 December 2007). "Portable Fixed-Width Integers in C". Retrieved 18 January 2016.
- ^ a b ISO/IEC 9899:1999 specification, TC3 (PDF). p. 255, § 7.18 Integer types <stdint.h>.
- ^ a b c d e f g h i j ISO/IEC 9899:1999 specification, TC3 (PDF). p. 22, § 5.2.4.2.one Sizes of integer types <limits.h>.
- ^ Rationale for International Standard—Programming Languages—C Revision 5.10 (PDF). p. 25, § 5.ii.four.ii.1 Sizes of integer types <limits.h>.
- ^ https://docs.microsoft.com/en-u.s./cpp/c-language/cpp-integer-limits?view=msvc-170.
- ^ a b ISO/IEC 9899:1999 specification, TC3 (PDF). p. 37, § six.two.6.1 Representations of types – General.
- ^ https://en.cppreference.com/west/cpp/language/integer_literal.
- ^ "64-Bit Programming Models: Why LP64?". The Open Group. Retrieved 9 November 2011.
- ^ ISO/IEC 9899:1999 specification, TC3 (PDF). p. 67, § six.v Expressions.
- ^ C11:The New C Standard, Thomas Plum
Source: https://en.wikipedia.org/wiki/C_data_types
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