Null-terminated byte strings
A null-terminated byte string (NTBS) is a sequence of nonzero bytes followed by a byte with value zero (the terminating null character). Each byte in a byte string encodes one character of some character set. For example, the character array {'\x63','\x61','\x74','\0'
} is an NTBS holding the string "cat"
in ASCII encoding.
Functions
Character classification |
|
Defined in header <ctype.h>
|
|
checks if a character is alphanumeric (function) | |
checks if a character is alphabetic (function) | |
checks if a character is lowercase (function) | |
checks if a character is an uppercase character (function) | |
checks if a character is a digit (function) | |
checks if a character is a hexadecimal character (function) | |
checks if a character is a control character (function) | |
checks if a character is a graphical character (function) | |
checks if a character is a space character (function) | |
(C99) |
checks if a character is a blank character (function) |
checks if a character is a printing character (function) | |
checks if a character is a punctuation character (function) | |
Character manipulation |
|
converts a character to lowercase (function) | |
converts a character to uppercase (function) |
Note: additional functions whose names begin with either to
or is
, followed by a lowercase letter, may be added to the header ctype.h
in future and should not be defined by programs that include that header.
ASCII values | characters | iscntrl |
isprint |
isspace |
isblank |
isgraph |
ispunct |
isalnum |
isalpha |
isupper |
islower |
isdigit |
isxdigit | ||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
decimal | hexadecimal | octal | |||||||||||||
0–8 | \x0 –\x8
|
\0 –\10
|
control codes (NUL , etc.)
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
9 | \x9
|
\11
|
tab (\t )
|
≠0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
10–13 | \xA –\xD
|
\12 –\15
|
whitespaces (\n , \v , \f , \r )
|
≠0
|
0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
14–31 | \xE –\x1F
|
\16 –\37
|
control codes | ≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
32 | \x20
|
\40
|
space | 0
|
≠0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
33–47 | \x21 –\x2F
|
\41 –\57
|
!"#$%&'()*+,-./
|
0
|
≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
48–57 | \x30 –\x39
|
\60 –\71
|
0123456789
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
0
|
0
|
0
|
≠0
|
≠0
|
58–64 | \x3A –\x40
|
\72 –\100
|
:;<=>?@
|
0
|
≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
65–70 | \x41 –\x46
|
\101 –\106
|
ABCDEF
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
≠0
|
≠0
|
0
|
0
|
≠0
|
71–90 | \x47 –\x5A
|
\107 –\132
|
GHIJKLMNOP
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
≠0
|
≠0
|
0
|
0
|
0
|
91–96 | \x5B –\x60
|
\133 –\140
|
[\]^_`
|
0
|
≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
97–102 | \x61 –\x66
|
\141 –\146
|
abcdef
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
≠0
|
0
|
≠0
|
0
|
≠0
|
103–122 | \x67 –\x7A
|
\147 –\172
|
ghijklmnop
|
0
|
≠0
|
0
|
0
|
≠0
|
0
|
≠0
|
≠0
|
0
|
≠0
|
0
|
0
|
123–126 | \x7B –\x7E
|
\172 –\176
|
}~ | 0
|
≠0
|
0
|
0
|
≠0
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
127 | \x7F
|
\177
|
backspace character (DEL )
|
≠0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
0
|
Conversions to numeric formats |
|
Defined in header <stdlib.h>
|
|
converts a byte string to a floating-point value (function) | |
(C99) |
converts a byte string to an integer value (function) |
(C99) |
converts a byte string to an integer value (function) |
(C99) |
converts a byte string to an unsigned integer value (function) |
(C99)(C99) |
converts a byte string to a floating point value (function) |
Defined in header <inttypes.h>
|
|
(C99)(C99) |
converts a byte string to intmax_t or uintmax_t (function) |
String manipulation |
|
Defined in header <string.h>
|
|
(C11) |
copies one string to another (function) |
(C11) |
copies a certain amount of characters from one string to another (function) |
(C11) |
concatenates two strings (function) |
(C11) |
concatenates a certain amount of characters of two strings (function) |
transform a string so that strcmp would produce the same result as strcoll (function) | |
String examination |
|
Defined in header <string.h>
|
|
(C11) |
returns the length of a given string (function) |
compares two strings (function) | |
compares a certain amount of characters of two strings (function) | |
compares two strings in accordance to the current locale (function) | |
finds the first occurrence of a character (function) | |
finds the last occurrence of a character (function) | |
returns the length of the maximum initial segment that consists of only the characters found in another byte string | |
returns the length of the maximum initial segment that consists of only the characters not found in another byte string | |
finds the first location of any character in one string, in another string (function) | |
finds the first occurrence of a substring of characters (function) | |
(C11) |
finds the next token in a byte string (function) |
Character array manipulation |
|
Defined in header <string.h>
|
|
searches an array for the first occurrence of a character (function) | |
compares two buffers (function) | |
(C11) |
fills a buffer with a character (function) |
(C11) |
copies one buffer to another (function) |
(C11) |
moves one buffer to another (function) |
Miscellaneous |
|
Defined in header <string.h>
|
|
(C11)(C11) |
returns a text version of a given error code (function) |
References
C11 standard (ISO/IEC 9899:2011):
- 7.4 Character handling (p: 200-204)
- 7.8 Format conversion of integer types (p: 217-220)
- 7.22 General utilities (p: 340-360)
- 7.24 String handling (p: 362-372)
- 7.31.2 Character handling (p: 455)
- 7.31.5 Format conversion of integer types (p: 455)
- 7.31.12 General utilities (p: 456)
- 7.31.13 String handling (p: 456)
- K.3.6 General utilities (p: 604=613)
- K.3.7 String handling (p: 614-623)
C99 standard (ISO/IEC 9899:1999):
- 7.4 Character handling (p: 181-185)
- 7.8 Format conversion of integer types (p: 198-201)
- 7.20 General utilities (p: 306-324)
- 7.21 String handling (p: 325-334)
- 7.26.2 Character handling (p: 401)
- 7.26.4 Format conversion of integer types (p: 401)
- 7.26.10 General utilities (p: 402)
- 7.26.11 String handling (p: 402)
C89/C90 standard (ISO/IEC 9899:1990):
- 4.3 CHARACTER HANDLING
- 4.10 GENERAL UTILITIES
- 4.11 STRING HANDLING
- 4.13.2 Character handling
- 4.13.7 General utilities
- 4.13.8 String handling
See also
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