diff --git a/include/string.h b/include/string.h
index 136fd9c..1cd8f35 100644
--- a/include/string.h
+++ b/include/string.h
@@ -3,29 +3,107 @@
 
 #include <stddef.h>
 
-/* memset() - fill memory with a constant byte. */
-extern void *memset(void *s, int c, size_t n);
-extern void *memcpy(void *dest, const void *src, size_t n);
+/* Copying functions. */
 
-/* strcat() - concatenate two string */
-extern char *strcat(char *dest, char const *src);
+/* Copy __n characters from __src to __dest (overlap not allowed). */
+extern void *memcpy(void *__dest, void const *__src, size_t __n);
 
-/* strcmp() - compare two strings */
-extern int strcmp(const char *s1, const char *s2);
-extern int strncmp(const char *s1, const char *s2, size_t n);
+/* Copy __n characters from __src to __dest (overlap allowed). */
+extern void *memmove(void *__dest, void const *__src, size_t __n);
 
-/* strcpy(), strncpy() - copy a string. */
-extern char *strncpy(char *dest, char const *str, size_t size);
-extern char *strcpy(char *dest, char const *src);
+/* Copy string __src into __dest. */
+extern char *strcpy(char * restrict __dest, char const * restrict __src);
 
-/* strlen - calculate the lenght of a string. */
-extern size_t strnlen(char const *str, size_t maxlen);
-extern size_t strlen(char const *str);
+/* Copy at most __n characters of __src into __dest. */
+extern char *strncpy(char * restrict __dest, char const * restrict __src,
+	size_t __n);
 
-/* strrchr() - find the last occurent of a byte */
-extern char *strrchr(const char *s, int c);
+/* Concatenation functions. */
 
-/* strdup() - dump string */
-extern char *strdup(const char *s);
+/* Copy __src at the end of __dest. */
+extern char *strcat(char * restrict __dest, char const * restrict __src);
+
+/* Copy at most __n characters of __src into __dest. */
+extern char *strncat(char * restrict __dest, char const * restrict __src,
+	size_t __n);
+
+/* Comparison functions. */
+
+/* Compare __n characters from __s1 and __s2. */
+extern int memcmp(void const *__s1, void const *__s2, size_t __n);
+
+/* Compare __s1 and __s2 as strings. */
+extern int strcmp(char const *__s1, char const *__s2);
+
+/* Compare __s1 and __s2 with locale-dependent collation rules. */
+extern int strcoll(char const *__s1, char const *__s2);
+
+/* Compare at most __n characters of __s1 and __s2. */
+extern int strncmp(char const *__s1, char const *__s2, size_t __n);
+
+/* Transform __src into __dest in a way that morphs strcoll into strcmp. */
+extern size_t strxfrm(char * restrict __dest, char const * restrict __src,
+	size_t __n);
+
+/* Search functions. */
+
+/* Search __c within the first __n characters of __s. */
+extern void *memchr(void const *__s, int __c, size_t __n);
+
+/* Find the first occurrence of __c within __s. */
+extern char *strchr(char const *__s, int __c);
+
+/* Count initial characters of __s that are not in __exclude. */
+extern char *strcspn(char const *__s, char const *__exclude);
+
+/* Find the first character of __s that is also in __include. */
+extern char *strpbrk(char const *__s, char const *__include);
+
+/* Find the last occurrence of __c within __s. */
+extern char *strrchr(char const *__s, int __c);
+
+/* Count initial characters of __s that are in __include. */
+extern char *strspn(char const *__s, char const *__include);
+
+/* Find the first occurrence of __s2 as a substring of __s1. */
+extern char *strstr(char const *__s1, char const *__s2);
+
+/* Break __s into tokens delimited by characters from __separators. */
+extern char *strtok(char * restrict __s, char const * restrict __separators);
+
+/* Miscellaneous functions. */
+
+/* Fill the __n first bytes of __s with character __c. */
+extern void *memset(void *__s, int __c, size_t __n);
+
+/* Returns a string that describes the errno value __errnum. */
+extern char *strerror(int __errnum);
+
+/* Length of __s. */
+extern size_t strlen(char const *__s);
+
+/*
+** Extensions
+*/
+
+/* The following functions are not specified by C99, but convenient. */
+
+/* Minimum of __n and the length of __s. */
+extern size_t strnlen(char const *__s, size_t __n);
+
+/* Like strchr, but returns the end of __s if __c is not found. */
+extern char *strchrnul(char const *__s, int __c);
+
+/* Compare __s1 and __s2 case-insensitively. */
+extern int strcasecmp(char const *__s1, char const *__s2);
+
+/* Compare at most __n characters of __s1 and __s2 case-insensitively. */
+extern int strncasecmp(char const *__s1, char const *__s2, size_t __n);
+
+/* Duplicate __s with malloc. */
+extern char *strdup(char const *__s);
+
+/* Duplicate at most __n characters of __s with malloc. */
+extern char *strndup(char const *__s, size_t __n);
 
 #endif /*__STRING_H__*/