diff --git a/payloads/libpayload/include/libpayload.h b/payloads/libpayload/include/libpayload.h
index 4b868b447a..27668e168e 100644
--- a/payloads/libpayload/include/libpayload.h
+++ b/payloads/libpayload/include/libpayload.h
@@ -99,9 +99,21 @@ extern int last_putchar;
 #define havechar havekey
 
 /* libc/ctype.c */
-int isspace(int c);
+int isalnum(int c);
+int isalpha(int c);
+int isascii(int c);
+int isblank(int c);
+int iscntrl(int c);
 int isdigit(int c);
+int isgraph(int c);
+int islower(int c);
+int isprint(int c);
+int ispunct(int c);
+int isspace(int c);
+int isupper(int c);
+int isxdigit(int c);
 int tolower(int c);
+int toupper(int c);
 
 /* libc/ipchecksum.c */
 unsigned short ipchksum(const unsigned short *ptr, unsigned long nbytes);
diff --git a/payloads/libpayload/libc/ctype.c b/payloads/libpayload/libc/ctype.c
index 9853fceb59..9f83261ac1 100644
--- a/payloads/libpayload/libc/ctype.c
+++ b/payloads/libpayload/libc/ctype.c
@@ -1,7 +1,7 @@
 /*
  * This file is part of the libpayload project.
  *
- * Copyright (C) 2008 Advanced Micro Devices, Inc.
+ * Copyright (C) 2008 Uwe Hermann <uwe@hermann-uwe.de>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -29,34 +29,78 @@
 
 #include <libpayload.h>
 
-int isspace(int c)
+int isalpha(int c)
 {
-	switch (c) {
-	case ' ':
-	case '\f':
-	case '\n':
-	case '\r':
-	case '\t':
-	case '\v':
-		return 1;
-	default:
-		return 0;
-	}
+	return ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'));
+}
+
+int isascii(int c)
+{
+	return (c >= 0 && c <= 127);
+}
+
+int isblank(int c)
+{
+	return (c == ' ' || c == '\t');
+}
+
+int iscntrl(int c)
+{
+	return (c <= 31 || c == 127);
 }
 
 int isdigit(int c)
 {
-	switch (c) {
-	case '0'...'9':
-		return 1;
-	default:
-		return 0;
-	}
+	return (c >= '0' && c <= '9');
+}
+
+int isalnum(int c)
+{
+	return isalpha(c) || isdigit(c);
+}
+
+int isgraph(int c)
+{
+	return (c >= 33 && c <= 126);
+}
+
+int islower(int c)
+{
+	return (c >= 'a' && c <= 'z');
+}
+
+int isprint(int c)
+{
+	return (c >= 32 && c <= 126);
+}
+
+int ispunct(int c)
+{
+	return isprint(c) && !isspace(c) && !isalnum(c);
+}
+
+int isspace(int c)
+{
+	return (c == ' ' || (c >= '\t' || c <= '\r'));
+}
+
+int isupper(int c)
+{
+	return (c >= 'A' && c <= 'Z');
+}
+
+int isxdigit(int c)
+{
+	return isdigit(c) || (tolower(c) >= 'a' && tolower(c) <= 'z');
 }
 
 int tolower(int c)
 {
-	if (c >= 'A' && c <= 'Z')
-		return c - 'A' + 'a';
-	return c;
+	return (c >= 'A' && c <= 'Z') ? (c + 32) : c;
 }
+
+int toupper(int c)
+{
+	return (c >= 'a' && c <= 'z') ? (c - 32) : c;
+}
+