diff --git a/src/core/ctype.c b/src/core/ctype.c
index 2941daf9..891af71e 100644
--- a/src/core/ctype.c
+++ b/src/core/ctype.c
@@ -35,11 +35,12 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 /**
  * Check to see if character is a space
  *
- * @v c			Character
+ * @v character		Character
  * @ret isspace		Character is a space
  */
-int isspace ( int c ) {
-	switch ( c ) {
+int isspace ( int character ) {
+
+	switch ( character ) {
 	case ' ' :
 	case '\f' :
 	case '\n' :
diff --git a/src/include/ctype.h b/src/include/ctype.h
index e92ecb1c..0d79ecd1 100644
--- a/src/include/ctype.h
+++ b/src/include/ctype.h
@@ -4,30 +4,114 @@
 /** @file
  *
  * Character types
+ *
  */
 
-FILE_LICENCE ( GPL2_OR_LATER );
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 
-#define isdigit(c)	((c) >= '0' && (c) <= '9')
-#define islower(c)	((c) >= 'a' && (c) <= 'z')
-#define isupper(c)	((c) >= 'A' && (c) <= 'Z')
-#define isxdigit(c)	(isdigit(c) || ((c) >= 'A' && (c) <= 'F') || ((c) >= 'a' && (c) <= 'f'))
-#define isprint(c)	((c) >= ' ' && (c) <= '~' )
+/**
+ * Check if character is a decimal digit
+ *
+ * @v character		ASCII character
+ * @ret is_digit	Character is a decimal digit
+ */
+static inline int isdigit ( int character ) {
 
-static inline unsigned char tolower(unsigned char c)
-{
-	if (isupper(c))
-		c -= 'A'-'a';
-	return c;
+	return ( ( character >= '0' ) && ( character <= '9' ) );
 }
 
-static inline unsigned char toupper(unsigned char c)
-{
-	if (islower(c))
-		c -= 'a'-'A';
-	return c;
+/**
+ * Check if character is a hexadecimal digit
+ *
+ * @v character		ASCII character
+ * @ret is_xdigit	Character is a hexadecimal digit
+ */
+static inline int isxdigit ( int character ) {
+
+	return ( ( ( character >= '0' ) && ( character <= '9' ) ) ||
+		 ( ( character >= 'A' ) && ( character <= 'F' ) ) ||
+		 ( ( character >= 'a' ) && ( character <= 'f' ) ) );
 }
 
-extern int isspace ( int c );
+/**
+ * Check if character is an upper-case letter
+ *
+ * @v character		ASCII character
+ * @ret is_upper	Character is an upper-case letter
+ */
+static inline int isupper ( int character ) {
+
+	return ( ( character >= 'A' ) && ( character <= 'Z' ) );
+}
+
+/**
+ * Check if character is a lower-case letter
+ *
+ * @v character		ASCII character
+ * @ret is_lower	Character is a lower-case letter
+ */
+static inline int islower ( int character ) {
+
+	return ( ( character >= 'a' ) && ( character <= 'z' ) );
+}
+
+/**
+ * Check if character is alphabetic
+ *
+ * @v character		ASCII character
+ * @ret is_alpha	Character is alphabetic
+ */
+static inline int isalpha ( int character ) {
+
+	return ( isupper ( character ) || islower ( character ) );
+}
+
+/**
+ * Check if character is alphanumeric
+ *
+ * @v character		ASCII character
+ * @ret is_alnum	Character is alphanumeric
+ */
+static inline int isalnum ( int character ) {
+
+	return ( isalpha ( character ) || isdigit ( character ) );
+}
+
+/**
+ * Check if character is printable
+ *
+ * @v character		ASCII character
+ * @ret is_print	Character is printable
+ */
+static inline int isprint ( int character ) {
+
+	return ( ( character >= ' ' ) && ( character <= '~' ) );
+}
+
+/**
+ * Convert character to lower case
+ *
+ * @v character		Character
+ * @v character		Lower-case character
+ */
+static inline int tolower ( int character ) {
+
+	return ( isupper ( character ) ?
+		 ( character - 'A' + 'a' ) : character );
+}
+
+/**
+ * Convert character to upper case
+ *
+ * @v character		Character
+ * @v character		Upper-case character
+ */
+static inline int toupper ( int character ) {
+
+	return ( islower ( character ) ?
+		 ( character - 'a' + 'A' ) : character );
+}
+
+extern int isspace ( int character );
 
 #endif /* _CTYPE_H */