How to Read Floats and Unsigned Ints From Text File C++

In the C programming language, information types plant the semantics and characteristics of storage of data elements. They are expressed in the language syntax in grade of declarations for memory locations or variables. Data types also determine the types of operations or methods of processing of information elements.

The C linguistic communication provides basic arithmetic types, such equally integer and real number types, and syntax to build array and compound types. Headers for the C standard library, to exist used via include directives, contain definitions of support types, that have additional properties, such equally providing storage with an exact size, contained of the language implementation on specific hardware platforms.^{[one] [2]}

Bones types [edit]

Main types [edit]

The C language provides the four basic arithmetics type specifiers char, int, float and double, and the modifiers signed, unsigned, short, and long. The following table lists the permissible combinations in specifying a large fix of storage size-specific declarations.

Type	Explanation	Minimum size ($.25)	Format specifier	Range	Suffix for decimal constants
char	Smallest addressable unit of measurement of the automobile that can contain basic character fix. It is an integer type. Actual type can exist either signed or unsigned. It contains CHAR_BIT $.25.[3]	8	%c	CHAR_MIN / CHAR_MAX	northward/a
signed char	Of the same size every bit char, just guaranteed to be signed. Capable of containing at least the [−127, +127] range.[3] [a]	8	%c (or %hhi for numerical output)	SCHAR_MIN / SCHAR_MAX [5]	n/a
unsigned char	Of the same size as char, but guaranteed to be unsigned. Contains at least the [0, 255] range.[vi]	8	%c (or %hhu for numerical output)	0 / UCHAR_MAX	n/a
brusk curt int signed curt signed short int	Short signed integer type. Capable of containing at least the [−32,767, +32,767] range.[3] [a]	16	%how-do-you-do or %hard disk drive	SHRT_MIN / SHRT_MAX	n/a
unsigned curt unsigned curt int	Brusque unsigned integer type. Contains at least the [0, 65,535] range.[3]	16	%hu	0 / USHRT_MAX	n/a
int signed signed int	Basic signed integer type. Capable of containing at least the [−32,767, +32,767] range.[three] [a]	16	%i or %d	INT_MIN / INT_MAX	none
unsigned unsigned int	Basic unsigned integer type. Contains at least the [0, 65,535] range.[3]	sixteen	%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, +2,147,483,647] range.[3] [a]	32	%li or %ld	LONG_MIN / LONG_MAX	l or L [seven]
unsigned long unsigned long int	Long unsigned integer blazon. Capable of containing at to the lowest degree the [0, 4,294,967,295] range.[3]	32	%lu	0 / ULONG_MAX	both u or U and l or L
long long long long int signed long long signed long long int	Long long signed integer blazon. Capable of containing at to the lowest degree the [−9,223,372,036,854,775,807, +9,223,372,036,854,775,807] 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 to the lowest degree the [0, +eighteen,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 blazon, ordinarily referred to as a single-precision floating-point type. Actual properties unspecified (except minimum limits); however, on most systems, this is the IEEE 754 single-precision binary floating-indicate format (32 $.25). This format is required past the optional Addendum F "IEC 60559 floating-point arithmetic".		Converting from text:[b] %f %F %g %K %e %E %a %A
double	Real floating-point blazon, usually referred to as a double-precision floating-indicate type. Actual properties unspecified (except minimum limits); however, on nearly systems, this is the IEEE 754 double-precision binary floating-point format (64 bits). This format is required past the optional Annex F "IEC 60559 floating-signal arithmetic".		%lf %lF %lg %lG %le %lE %la %lA [c]
long double	Real floating-indicate blazon, commonly mapped to an extended precision floating-signal number format. Actual backdrop unspecified. It can be either x86 extended-precision floating-bespeak format (80 bits, but typically 96 bits or 128 bits in retentiveness with padding bytes), the non-IEEE "double-double" (128 $.25), IEEE 754 quadruple-precision floating-point format (128 $.25), or the aforementioned as double. See the article on long double for details.		%Lf %LF %Lg %LG %Le %LE %La %LA [c]

1. ^ ^{a b c d e} The minimal ranges −(2^{due north−one}−1) to iiⁿ⁻¹−i (e.g. [−127,127]) come from the diverse integer representations allowed by the standard (ones' complement, sign-magnitude, 2'due south complement).^[iv] Even so, most platforms use 2's complement, implying a range of the form −2^thousand−1 to two^thousand−i−one with m ≥ northward for these implementations, e.thousand. [−128,127] (SCHAR_MIN = −128 and SCHAR_MAX = 127) for an eight-fleck signed char.
2. ^ These format strings also be for formatting to text, but operate on a double.
3. ^ ^{a b} Upper-case letter differs from lowercase in the output. Upper-case letter specifiers produce values in the upper-case letter, and lowercase in lower (%A, %E, %F, %1000 produce such values as INF, NAN and E (exponent) in uppercase)

The actual size of the integer types varies by implementation. The standard requires only size relations between the information 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 short. As char's size is e'er the minimum supported information type, no other data types (except chip-fields) can exist smaller.

The minimum size for char is 8 bits, the minimum size for brusque and int is xvi bits, for long it is 32 $.25 and long long must comprise at least 64 bits.

The type int should be the integer type that the target processor is most efficiently working with. This allows peachy flexibility: for example, all types tin be 64-scrap. Nevertheless, several different integer width schemes (data models) are popular. Because the data model defines how different programs communicate, a uniform data model is used within a given operating system application interface.^[8]

In practice, char is usually viii bits in size and short is usually 16 bits in size (as are their unsigned counterparts). This holds true for platforms as diverse as 1990s SunOS 4 Unix, Microsoft MS-DOS, modern Linux, and Microchip MCC18 for embedded viii-bit Picture show microcontrollers. POSIX requires char to exist exactly 8 $.25 in size.

Diverse rules in the C standard make unsigned char the basic type used for arrays suitable to store arbitrary non-bit-field objects: its lack of padding bits and trap representations, the definition of object representation,^[6] and the possibility of aliasing.^[9]

The actual size and beliefs of floating-point types also vary by implementation. The only guarantee is that long double is non smaller than double, which is non smaller than bladder. Usually, the 32-chip and 64-bit IEEE 754 binary floating-betoken formats are used.

The C99 standard includes new real floating-signal types float_t and double_t, divers in <math.h>. They correspond 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 type [edit]

C99 added a boolean (true/false) type _Bool. Additionally, the <stdbool.h> header defines bool as a convenient allonym for this blazon, and also provides macros for true and imitation. _Bool functions similarly to a normal integer blazon, with one exception: whatever assignments to a _Bool that are not 0 (simulated) are stored as 1 (true). This behavior exists to avoid integer overflows in implicit narrowing conversions. For example, in the post-obit code:

                        unsigned                                    char                                    b                                    =                                    256            ;                        if                                    (            b            )                                    {                                                /* do something */                        }                      

Variable b evaluates to fake if unsigned char has a size of 8 bits. This is because the value 256 does not fit in the data type, which results in the lower 8 bits of it existence used, resulting in a nil value. Nevertheless, irresolute the type causes the previous code to behave normally:

                        _Bool                                    b                                    =                                    256            ;                        if                                    (            b            )                                    {                                                /* do something */                        }                      

The type _Bool as well ensures true values always compare equal to each other:

                        _Bool                                    a                                    =                                    1            ,                                    b                                    =                                    2            ;                        if                                    (            a                                    ==                                    b            )                                    {                                                /* do something */                        }                      

Size and pointer difference types [edit]

The C language specification includes the typedefdue south size_t and ptrdiff_t to represent memory-related quantities. Their size is divers co-ordinate to the target processor'due south arithmetic capabilities, not the memory capabilities, such equally available address infinite. Both of these types are divers in the <stddef.h> header (cstddef in C++).

size_t is an unsigned integer type used to represent the size of whatever object (including arrays) in the particular implementation. The operator sizeof yields a value of the blazon size_t. The maximum size of size_t is provided via SIZE_MAX, a macro constant which is divers in the <stdint.h> header (cstdint header in C++). size_t is guaranteed to be at least xvi $.25 wide. Additionally, POSIX includes ssize_t, which is a signed integer type of the aforementioned width as size_t.

ptrdiff_t is a signed integer type used to correspond the deviation between pointers. It is guaranteed to be valid only against pointers of the same type; subtraction of pointers consisting of different types is implementation-divers.

Interface to the properties of the basic types [edit]

Information about the actual properties, such every bit size, of the basic arithmetic types, is provided via macro constants in ii headers: <limits.h> header (climits header in C++) defines macros for integer types and <bladder.h> header (cfloat header in C++) defines macros for floating-betoken types. The actual values depend on the implementation.

Backdrop of integer types [edit]

• CHAR_BIT – size of the char type in bits (at least eight $.25)
• 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 grapheme

Properties 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 float, double, long double respectively
• FLT_MAX, DBL_MAX, LDBL_MAX – maximum finite value of bladder, double, long double, respectively
• FLT_ROUNDS – rounding way for floating-signal operations
• FLT_EVAL_METHOD (C99) – evaluation method of expressions involving dissimilar floating-point types
• FLT_RADIX – radix of the exponent in the floating-point types
• FLT_DIG, DBL_DIG, LDBL_DIG – number of decimal digits that can be represented without losing precision by float, double, long double, respectively
• FLT_EPSILON, DBL_EPSILON, LDBL_EPSILON – deviation between 1.0 and the adjacent representable value of float, double, long double, respectively
• FLT_MANT_DIG, DBL_MANT_DIG, LDBL_MANT_DIG – number of FLT_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 that FLT_RADIX raised 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 10 raised to that power is a normalized float, double, long double, respectively
• FLT_MAX_EXP, DBL_MAX_EXP, LDBL_MAX_EXP – maximum positive integer such that FLT_RADIX raised to a power ane 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 x raised to that ability is a normalized float, double, long double, respectively
• DECIMAL_DIG (C99) – minimum number of decimal digits such that any number of the widest supported floating-point type tin be represented in decimal with a precision of DECIMAL_DIG digits and read back in the original floating-bespeak type without changing its value. DECIMAL_DIG is at least 10.

Stock-still-width integer types [edit]

The C99 standard includes definitions of several new integer types to enhance the portability of programs.^[two] The already bachelor basic integer types were deemed bereft, because their bodily sizes are implementation defined and may vary beyond different systems. The new types are especially useful in embedded environments where hardware normally supports only several types and that back up varies between unlike environments. All new types are defined in <inttypes.h> header (cinttypes header in C++) and also are bachelor at <stdint.h> header (cstdint header in C++). The types can exist grouped into the following categories:

• Exact-width integer types that are guaranteed to have the aforementioned number n of $.25 across all implementations. Included only if it is available in the implementation.
• Least-width integer types that are guaranteed to exist the smallest blazon available in the implementation, that has at least specified number n of bits. Guaranteed to be specified for at least N=eight,16,32,64.
• Fastest integer types that are guaranteed to exist the fastest integer type bachelor in the implementation, that has at least specified number n of bits. Guaranteed to be specified for at least Northward=8,16,32,64.
• Pointer integer types that are guaranteed to be able to hold a pointer. Included only if it is available in the implementation.
• Maximum-width integer types that are guaranteed to be the largest integer blazon in the implementation.

The post-obit tabular array summarizes the types and the interface to acquire the implementation details (north refers to the number of $.25):

Blazon category	Signed types			Unsigned types
	Type	Minimum value	Maximum value	Type	Minimum value	Maximum value
Exact width	intn_t	INTnorth_MIN	INTdue north_MAX	uintnorth_t	0	UINTdue north_MAX
Least width	int_leastnorth_t	INT_LEASTnorthward_MIN	INT_LEASTdue north_MAX	uint_leastn_t	0	UINT_LEASTn_MAX
Fastest	int_fastn_t	INT_FASTnorthward_MIN	INT_FASTn_MAX	uint_fastnorthward_t	0	UINT_FASTn_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 enhance the functionality of the types divers in the <stdint.h> header. It defines macros for printf format string and scanf format cord specifiers respective 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 cord

The macros are in the format PRI{fmt}{type} . Here {fmt} defines the output formatting and is i of d (decimal), 10 (hexadecimal), o (octal), u (unsigned) and i (integer). {blazon} defines the type of the argument and is ane of n , FASTnorthward , LEASTn , PTR, MAX, where northward corresponds to the number of bits in the argument.

Scanf format cord

The macros are in the format SCN{fmt}{type} . Hither {fmt} defines the output formatting and is 1 of d (decimal), x (hexadecimal), o (octal), u (unsigned) and i (integer). {type} defines the blazon of the statement and is one of n , FASTdue north , To the lowest degreen , PTR, MAX, where n corresponds to the number of bits in the argument.

Functions

This section needs expansion. You can assist by calculation to it. (Oct 2011)

Additional floating-point 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:

• _FloatN for binary interchange formats;
• _DecimalN for decimal interchange formats;
• _FloatDue northx for binary extended formats;
• _DecimalNx for decimal extended formats.

Structures [edit]

Structures amass the storage of multiple data items, of potentially differing data types, into one memory block referenced past a unmarried variable. The post-obit case declares the data blazon struct birthday which contains the name and birthday of a person. The structure definition is followed past a declaration of the variable John that allocates the needed storage.

                        struct            altogether                                    {                                                char                                    proper name            [            20            ];                                                int                                    solar day            ;                                                int                                    month            ;                                                int                                    year            ;                        };                        struct            birthday                                    John            ;                      

The memory layout of a construction is a language implementation result for each platform, with a few restrictions. The memory accost of the start member must be the same as the accost of structure itself. Structures may exist initialized or assigned to using compound literals. A part may directly return a structure, although this is ofttimes non efficient at run-time. Since C99, a structure may also end with a flexible array member.

A structure containing a pointer to a structure of its own blazon is commonly used to build linked data structures:

                        struct            node                                    {                                                int                                    val            ;                                                struct            node                                    *            next            ;                        };                      

Arrays [edit]

For every type T, except void and function types, there exist the types "assortment of Northward elements of type T". An array is a collection of values, all of the aforementioned blazon, stored contiguously in memory. An array of size N is indexed past integers from 0 upward to and including North−1. Here is a cursory example:

                        int                                    true cat            [            10            ];                                    // array of ten elements, each of blazon int          

Arrays can exist initialized with a chemical compound initializer, only not assigned. Arrays are passed to functions by passing a pointer to the first element. Multidimensional arrays are divers as "array of array …", and all except the outermost dimension must have compile-time abiding size:

                        int                                    a            [            10            ][            eight            ];                                    // array of 10 elements, each of type 'array of eight int elements'          

Pointers [edit]

Every data blazon T has a respective blazon arrow to T . A pointer is a data type that contains the address of a storage location of a variable of a particular type. They are declared with the asterisk (*) blazon declarator following the basic storage type and preceding the variable name. Whitespace before or after the asterisk is optional.

                        char                                    *            square            ;                        long                                    *            circle            ;                        int                                    *            oval            ;                      

Pointers may also be alleged for pointer information types, thus creating multiple indirect pointers, such as char ** and int ***, including pointers to assortment types. The latter are less mutual than an assortment of pointers, and their syntax may be confusing:

                        char                                    *            pc            [            10            ];                                    // assortment of x elements of 'pointer to char'            char                                    (            *            pa            )[            x            ];                                    // pointer to a 10-element array of char          

The element pc requires x blocks of memory of the size of pointer to char (usually 40 or 80 bytes on common platforms), but element pa is simply 1 arrow (size 4 or 8 bytes), and the data information technology refers to is an array of 10 bytes ( sizeof * pa == 10 ).

Unions [edit]

A union blazon is a special construct that permits access to the aforementioned retentiveness cake by using a choice of differing blazon descriptions. For example, a union of data types may exist alleged to permit reading the aforementioned data either as an integer, a float, or any other user alleged type:

                        union            {                                                int                                    i            ;                                                float                                    f            ;                                                struct            {                                                unsigned                                    int                                    u            ;                                                double                                    d            ;                                                }                                    s            ;                        }                                    u            ;                      

The full size of u is the size of u.due south – which happens to be the sum of the sizes of u.s.u and united statesd – since s 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 union member is not the same as casting since the value of the member is not converted, merely merely read.

Function pointers [edit]

Office pointers allow referencing functions with a particular signature. For example, to shop the address of the standard function abs in the variable my_int_f:

                        int                                    (            *            my_int_f            )(            int            )                                    =                                    &            abs            ;                        // the & operator can be omitted, but makes clear that the "address of" abs is used here          

Office pointers are invoked past proper name just like normal function calls. Part pointers are separate from pointers and void pointers.

Type qualifiers [edit]

The aforementioned types tin be characterized further by blazon qualifiers, yielding a qualified type. Every bit of 2014^[update] and C11, in that location are four blazon 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] simply 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 nearly used, appearing in the standard library and encountered in any significant use of the C linguistic communication, which must satisfy const-correctness. The other qualifiers are used for low-level programming, and while widely used at that place, are rarely used by typical programmers.^{[ citation needed ]}

See as well [edit]

• C syntax
• Uninitialized variable
• Integer (computer scientific discipline)

References [edit]

1. ^ Barr, Michael (2 December 2007). "Portable Stock-still-Width Integers in C". Retrieved 18 Jan 2016.
2. ^ ^{a b} ISO/IEC 9899:1999 specification, TC3 (PDF). p. 255, § 7.xviii Integer types <stdint.h>.
3. ^ ^{a b c d e f g h i j} ISO/IEC 9899:1999 specification, TC3 (PDF). p. 22, § 5.2.4.2.1 Sizes of integer types <limits.h>.
4. ^ Rationale for International Standard—Programming Languages—C Revision v.ten (PDF). p. 25, § 5.ii.4.2.1 Sizes of integer types <limits.h>.
5. ^ https://docs.microsoft.com/en-u.s.a./cpp/c-language/cpp-integer-limits?view=msvc-170.
6. ^ ^{a b} ISO/IEC 9899:1999 specification, TC3 (PDF). p. 37, § 6.2.6.1 Representations of types – General.
7. ^ https://en.cppreference.com/westward/cpp/language/integer_literal.
8. ^ "64-Fleck Programming Models: Why LP64?". The Open up Group. Retrieved 9 Nov 2011.
9. ^ ISO/IEC 9899:1999 specification, TC3 (PDF). p. 67, § 6.5 Expressions.
10. ^ C11:The New C Standard, Thomas Plum

How to Read Floats and Unsigned Ints From Text File C++

Source: https://en.wikipedia.org/wiki/C_data_types

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