Index: src/OFString.h
==================================================================
--- src/OFString.h
+++ src/OFString.h
@@ -131,6 +131,16 @@
 
 /**
  * Reverse the OFString.
  */
 - reverse;
+
+/**
+ * Upper the OFString.
+ */
+- upper;
+
+/**
+ * Lower the OFString.
+ */
+- lower;
 @end

Index: src/OFString.m
==================================================================
--- src/OFString.m
+++ src/OFString.m
@@ -207,8 +207,28 @@
 		string[i] ^= string[j];
 		string[j] ^= string[i];
 		string[i] ^= string[j];
 	}
 
+	return self;
+}
+
+- upper
+{
+	size_t i = length;
+
+	while (i--) 
+		string[i] = towupper(string[i]);
+
+	return self;
+}
+
+- lower
+{
+	size_t i = length;
+
+	while (i--) 
+		string[i] = towlower(string[i]);
+
 	return self;
 }
 @end

Index: tests/OFString/OFString.m
==================================================================
--- tests/OFString/OFString.m
+++ tests/OFString/OFString.m
@@ -61,13 +61,27 @@
 		puts("Reversed s1 is expected string! GOOD!");
 	else {
 		puts("Reversed s1 is NOT the expected string!");
 		return 1;
 	}
+
+	if (!strcmp([[s1 upper] cString], "321TSET"))
+		puts("Upper s1 is expected string! GOOD!");
+	else {
+		puts("Upper s1 is NOT expected string!");
+		return 1;
+	}
+
+	if (!strcmp([[s1 lower] cString], "321tset"))
+		puts("Lower s1 is expected string! GOOD!");
+	else {
+		puts("Lower s1 is NOT expected string!");
+		return 1;
+	}
 
 	[s1 free];
 	[s2 free];
 	[s3 free];
 	[s4 free];
 
 	return 0;
 }