'strings' should be 'string'.

21-shell/libc/string.h

@@ -1,5 +1,5 @@
-#ifndef STRINGS_H
-#define STRINGS_H
+#ifndef STRING_H
+#define STRING_H
 
 void int_to_ascii(int n, char str[]);
 void reverse(char s[]);

22-malloc/README.md

@@ -15,7 +15,7 @@ our first page starts at 0x10000 (as hardcoded on `mem.c`) and
 subsequent `kmalloc()`'s produce a new address which is
 aligned 4096 bytes or 0x1000 from the previous one.
 
-Note that we added a new `strings.c:hex_to_ascii()` for
+Note that we added a new `string.c:hex_to_ascii()` for
 nicer printing of hex numbers.
 
 Another cosmetic modification is to rename `types.c` to 

22-malloc/libc/string.h

@@ -1,5 +1,5 @@
-#ifndef STRINGS_H
-#define STRINGS_H
+#ifndef STRING_H
+#define STRING_H
 
 void int_to_ascii(int n, char str[]);
 void hex_to_ascii(int n, char str[]);

23-fixes/libc/string.h

@@ -1,5 +1,5 @@
-#ifndef STRINGS_H
-#define STRINGS_H
+#ifndef STRING_H
+#define STRING_H
 
 void int_to_ascii(int n, char str[]);
 void hex_to_ascii(int n, char str[]);