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+
+# complex.h - complex number support
+
+Not supported/implemented
diff --git a/doc/ctype.md b/doc/ctype.md
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+
+# ctype.h - Classification of ASCII characters
+
+Function declarations:
+
+- [isalnum](#isalnum)
+- [isalpha](#isalpha)
+- [isblank](#isblank)
+- [iscntrl](#iscntrl)
+- [isdigit](#isdigit)
+- [isgraph](#isgraph)
+- [islower](#islower)
+- [isprint](#isprint)
+- [ispunct](#ispunct)
+- [isspace](#isspace)
+- [isupper](#isupper)
+- [isxdigit](#isxdigit)
+- [tolower](#tolower)
+- [toupper](#toupper)
+
+## [isalnum](#isalnum)
+
+Description
+
+Function checks whether given integer is an ASCII code representing a letter or
+a digit. These characters are lowercase letters ('a'..'z'), uppercase letters
+('A'..'Z') and digits ('0'..'9').
+
+Declaration
+
+```c
+int isalnum(int c);
+```
+
+Description
+
+Function checks whether given integer is an ASCII code representing a letter.
+These characters are lowercase letters ('a'..'z') and uppercase letters.
+
+Declaration
+
+```c
+int isalpha(int c);
+```
+
+Description
+
+Checks whether a character is a space (' ') or a horizontal tab ('\t')
+
+Declaration
+
+```c
+int isblank(int c);
+```
+
+Description
+
+Checks whether a character is a control character
+('\x00' through '\x1f' and '\x7f').
+
+Declaration
+
+```c
+int iscntrl(int c);
+```
+
+Description
+
+Checks whether a character is a digit ('0' through '9')
+
+Declaration
+
+```c
+int isdigit(int c);
+```
+Description
+
+Checks whether a character is a hexadecimal digit ('0' through '9', 'a' through 'f' or 'A' through 'F')
+
+Declaration
+
+```c
+int isxdigit(int c);
+```
+Description
+
+Checks whether a character is a
+
+- Number;
+- Letter;
+- or punctuation
+
+Declaration
+
+```c
+int isgraph(int c);
+```
+Description
+
+Checks whether a character is a lowercase letter ('a' through 'z')
+
+Declaration
+
+```c
+int islower(int c);
+```
+Description
+
+Checks whether a character is a uppercase letter ('A' through 'Z')
+
+Declaration
+
+```c
+int islower(int c);
+```
+Description
+
+Checks whether a character is a
+
+- Number;
+- Letter;
+- Space;
+- or punctuation
+
+Declaration
+
+```c
+int isprint(int c);
+```
+Description
+
+Checks whether a character is a punctuation character (one of `!"#$%&'()*+,-./:;<=>?@[\]^_{|}~`
+or backtick).
+
+Declaration
+
+```c
+int ispunct(int c);
+```
+Description
+
+Function checks whether given integer is a whitespace character. These
+characters include whitespace (' '), form feed ('\f'), line feed ('\n'),
+carriage return ('\r'), horizontal and vertical tab ('\t' and '\v').
+
+Declaration
+
+```c
+int isspace(int c);
+```
+
+Description
+
+If the character is an uppercase letter returns lowercase version of it. Otherwise
+returns the character unmodified.
+
+Declaration
+
+```c
+int tolower(int c);
+```
+Description
+
+If the character is an lowercase letter returns uppercase version of it. Otherwise
+returns the character unmodified.
+
+Declaration
+
+```c
+int toupper(int c);
+```
+