diff --git a/asm.h b/asm.h
index b8a7353..49eab70 100644
--- a/asm.h
+++ b/asm.h
@@ -14,5 +14,5 @@
                 (0xC0 | (((lim) >> 28) & 0xf)), (((base) >> 24) & 0xff)
 
 #define STA_X     0x8       // Executable segment
-#define STA_W     0x2       // Writeable (non-executable segments)
+#define STA_W     0x2       // Writable (non-executable segments)
 #define STA_R     0x2       // Readable (executable segments)
diff --git a/bootasm.S b/bootasm.S
index 8d394aa..7feb21b 100644
--- a/bootasm.S
+++ b/bootasm.S
@@ -43,7 +43,6 @@ seta20.2:
   orl     $CR0_PE, %eax
   movl    %eax, %cr0
 
-//PAGEBREAK!
   # Complete the transition to 32-bit protected mode by using a long jmp
   # to reload %cs and %eip.  The segment descriptors are set up with no
   # translation, so that the mapping is still the identity mapping.
diff --git a/elf.h b/elf.h
index d16c967..f65f744 100644
--- a/elf.h
+++ b/elf.h
@@ -32,11 +32,3 @@ struct proghdr {
   uint flags;
   uint align;
 };
-
-// Values for Proghdr type
-#define ELF_PROG_LOAD           1
-
-// Flag bits for Proghdr flags
-#define ELF_PROG_FLAG_EXEC      1
-#define ELF_PROG_FLAG_WRITE     2
-#define ELF_PROG_FLAG_READ      4
diff --git a/main.c b/main.c
index 808545d..fc54b83 100644
--- a/main.c
+++ b/main.c
@@ -1,8 +1,6 @@
 #include "types.h"
 #include "x86.h"
 
-extern char end[]; // first address after kernel loaded from ELF file
-
 int
 halt(void)
 {
diff --git a/mmu.h b/mmu.h
index bcf3fe0..d5113b3 100644
--- a/mmu.h
+++ b/mmu.h
@@ -6,7 +6,4 @@
 
 // various segment selectors.
 #define SEG_KCODE 1  // kernel code
-#define SEG_KDATA 2  // kernel data+stack
-#define SEG_UCODE 3  // user code
-#define SEG_UDATA 4  // user data+stack
-#define SEG_TSS   5  // this process's task state
\ No newline at end of file
+#define SEG_KDATA 2  // kernel data+stack
\ No newline at end of file
diff --git a/param.h b/param.h
index 3b66684..f756028 100644
--- a/param.h
+++ b/param.h
@@ -1,3 +1 @@
 #define KSTACKSIZE 4096  // size of per-process kernel stack
-#define NCPU          8  // maximum number of CPUs
-
diff --git a/x86.h b/x86.h
index 9b2984f..765ee17 100644
--- a/x86.h
+++ b/x86.h
@@ -30,15 +30,6 @@ outw(ushort port, ushort data)
   asm volatile("out %0,%1" : : "a" (data), "d" (port));
 }
 
-static inline void
-outsl(int port, const void *addr, int cnt)
-{
-  asm volatile("cld; rep outsl" :
-               "=S" (addr), "=c" (cnt) :
-               "d" (port), "0" (addr), "1" (cnt) :
-               "cc");
-}
-
 static inline void
 stosb(void *addr, int data, int cnt)
 {
@@ -47,12 +38,3 @@ stosb(void *addr, int data, int cnt)
                "0" (addr), "1" (cnt), "a" (data) :
                "memory", "cc");
 }
-
-static inline void
-stosl(void *addr, int data, int cnt)
-{
-  asm volatile("cld; rep stosl" :
-               "=D" (addr), "=c" (cnt) :
-               "0" (addr), "1" (cnt), "a" (data) :
-               "memory", "cc");
-}
\ No newline at end of file