# Null-terminated byte strings

From cppreference.com
< cpp‎ | string

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 `<cctype>`
isalnum | checks if a character is alphanumeric (function)
isalpha | checks if a character is alphabetic (function)
islower | checks if a character is lowercase (function)
isupper | checks if a character is an uppercase character (function)
isdigit | checks if a character is a digit (function)
isxdigit | checks if a character is a hexadecimal character (function)
iscntrl | checks if a character is a control character (function)
isgraph | checks if a character is a graphical character (function)
isspace | checks if a character is a space character (function)
isblank (C++11) | checks if a character is a blank character (function)
isprint | checks if a character is a printing character (function)
ispunct | checks if a character is a punctuation character (function)

##### Character manipulation

tolower | converts a character to lowercase (function)
toupper | converts a character to uppercase (function)

ASCII values (hex) | characters | `iscntrl` `iswcntrl` | `isprint` `iswprint` | `isspace` `iswspace` | `isblank` `iswblank` | `isgraph` `iswgraph` | `ispunct` `iswpunct` | `isalnum` `iswalnum` | `isalpha` `iswalpha` | `isupper` `iswupper` | `islower` `iswlower` | `isdigit` `iswdigit` | `isxdigit` `iswxdigit`
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
0 - 8 | `0x00-0x08` | control codes (`NUL`, etc.) | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
9 | `0x09` | tab (`\t`) | `≠0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
10 - 13 | `0x0A-0x0D` | whitespaces (`\n`,`\v`,`\f`,`\r`) | `≠0` | `0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
14 - 31 | `0x0E-0x1F` | control codes | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
32 | `0x20` | space | `0` | `≠0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`
33 - 47 | `0x21-0x2F` | `!"#$%&'()*+,-./` | `0` | `≠0` | `0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0`
48 - 57 | `0x30-0x39` | `0123456789` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `0` | `0` | `0` | `≠0` | `≠0`
58 - 64 | `0x3a-0x40` | `:;<=>?@` | `0` | `≠0` | `0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0`
65 - 70 | `0x41-0x46` | `ABCDEF` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `≠0` | `≠0` | `0` | `0` | `≠0`
71 - 90 | `0x47-0x5A` | `GHIJKLMNOPQRSTUVWXYZ` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `≠0` | `≠0` | `0` | `0` | `0`
91 - 96 | `0x5B-0x60` | `[\]^_`` | `0` | `≠0` | `0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0`
97 -102 | `0x61-0x66` | `abcdef` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `≠0` | `0` | `≠0` | `0` | `≠0`
103-122 | `0x67-0x7A` | `ghijklmnopqrstuvwxyz` | `0` | `≠0` | `0` | `0` | `≠0` | `0` | `≠0` | `≠0` | `0` | `≠0` | `0` | `0`
123-126 | `0x7B-0x7E` | `{|}~` | `0` | `≠0` | `0` | `0` | `≠0` | `≠0` | `0` | `0` | `0` | `0` | `0` | `0`
127 | `0x7F` | backspace character (`DEL`) | `≠0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0` | `0`

##### Conversions to numeric formats

Defined in header `<cstdlib>`
atof | converts a byte string to a floating point value (function)
atoi atol atoll | converts a byte string to an integer value (function)
strtol strtoll | converts a byte string to an integer value (function)
strtoul strtoull | converts a byte string to an unsigned integer value (function)
strtof strtod strtold | converts a byte string to a floating point value (function)
Defined in header `<cinttypes>`
strtoimax strtoumax (C++11)(C++11) | converts a byte string to std::intmax_t or std::uintmax_t (function)

##### String manipulation

Defined in header `<cstring>`
strcpy | copies one string to another (function)
strncpy | copies a certain amount of characters from one string to another (function)
strcat | concatenates two strings (function)
strncat | concatenates a certain amount of characters of two strings (function)
strxfrm | transform a string so that strcmp would produce the same result as strcoll (function)

##### String examination

Defined in header `<cstring>`
strlen | returns the length of a given string (function)
strcmp | compares two strings (function)
strncmp | compares a certain amount of characters of two strings (function)
strcoll | compares two strings in accordance to the current locale (function)
strchr | finds the first occurrence of a character (function)
strrchr | finds the last occurrence of a character (function)
strspn | returns the length of the maximum initial segment that consists of only the characters found in another byte string (function)
strcspn | returns the length of the maximum initial segment that consists of only the characters not found in another byte string (function)
strpbrk | finds the first location of any character from a set of separators (function)
strstr | finds the first occurrence of a substring of characters (function)
strtok | finds the next token in a byte string (function)

##### Character array manipulation

Defined in header `<cstring>`
memchr | searches an array for the first occurrence of a character (function)
memcmp | compares two buffers (function)
memset | fills a buffer with a character (function)
memcpy | copies one buffer to another (function)
memmove | moves one buffer to another (function)

##### Miscellaneous

Defined in header `<cstring>`
strerror | returns a text version of a given error code (function)

### See also

C documentation for Null-terminated byte strings

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