diff --git a/kernel/console.c b/kernel/console.c
index 56a6799..1e8d355 100644
--- a/kernel/console.c
+++ b/kernel/console.c
@@ -149,7 +149,7 @@ consoleintr(int c)
     }
     break;
   case C('H'): // Backspace
-  case '\x7f':
+  case '\x7f': // Delete key
     if(cons.e != cons.w){
       cons.e--;
       consputc(BACKSPACE);
diff --git a/kernel/proc.c b/kernel/proc.c
index eb667a5..580b3b6 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -171,8 +171,8 @@ freeproc(struct proc *p)
   p->state = UNUSED;
 }
 
-// Create a user page table for a given process,
-// with no user memory, but with trampoline pages.
+// Create a user page table for a given process, with no user memory,
+// but with trampoline and trapframe pages.
 pagetable_t
 proc_pagetable(struct proc *p)
 {
@@ -193,7 +193,8 @@ proc_pagetable(struct proc *p)
     return 0;
   }
 
-  // map the trapframe just below TRAMPOLINE, for trampoline.S.
+  // map the trapframe page just below the trampoline page, for
+  // trampoline.S.
   if(mappages(pagetable, TRAPFRAME, PGSIZE,
               (uint64)(p->trapframe), PTE_R | PTE_W) < 0){
     uvmunmap(pagetable, TRAMPOLINE, 1, 0);
diff --git a/kernel/syscall.c b/kernel/syscall.c
index c1b3670..95b9f70 100644
--- a/kernel/syscall.c
+++ b/kernel/syscall.c
@@ -83,27 +83,27 @@ argstr(int n, char *buf, int max)
   return fetchstr(addr, buf, max);
 }
 
-extern uint64 sys_chdir(void);
-extern uint64 sys_close(void);
-extern uint64 sys_dup(void);
-extern uint64 sys_exec(void);
-extern uint64 sys_exit(void);
 extern uint64 sys_fork(void);
-extern uint64 sys_fstat(void);
-extern uint64 sys_getpid(void);
-extern uint64 sys_kill(void);
-extern uint64 sys_link(void);
-extern uint64 sys_mkdir(void);
-extern uint64 sys_mknod(void);
-extern uint64 sys_open(void);
+extern uint64 sys_exit(void);
+extern uint64 sys_wait(void);
 extern uint64 sys_pipe(void);
 extern uint64 sys_read(void);
+extern uint64 sys_kill(void);
+extern uint64 sys_exec(void);
+extern uint64 sys_fstat(void);
+extern uint64 sys_chdir(void);
+extern uint64 sys_dup(void);
+extern uint64 sys_getpid(void);
 extern uint64 sys_sbrk(void);
 extern uint64 sys_sleep(void);
-extern uint64 sys_unlink(void);
-extern uint64 sys_wait(void);
-extern uint64 sys_write(void);
 extern uint64 sys_uptime(void);
+extern uint64 sys_open(void);
+extern uint64 sys_write(void);
+extern uint64 sys_mknod(void);
+extern uint64 sys_unlink(void);
+extern uint64 sys_link(void);
+extern uint64 sys_mkdir(void);
+extern uint64 sys_close(void);
 
 static uint64 (*syscalls[])(void) = {
 [SYS_fork]    sys_fork,