diff --git a/console.c b/console.c
index 16d0e7a..1d51a3c 100644
--- a/console.c
+++ b/console.c
@@ -18,8 +18,8 @@ static void consputc(int);
 static int panicked = 0;
 
 static struct {
-	struct spinlock lock;
-	int locking;
+  struct spinlock lock;
+  int locking;
 } cons;
 
 static void
diff --git a/exec.c b/exec.c
index 4f11695..39530aa 100644
--- a/exec.c
+++ b/exec.c
@@ -30,7 +30,7 @@ exec(char *path, char **argv)
   if(elf.magic != ELF_MAGIC)
     goto bad;
 
-  if (!(pgdir = setupkvm()))
+  if(!(pgdir = setupkvm()))
     goto bad;
 
   // Load program into memory.
@@ -41,11 +41,11 @@ exec(char *path, char **argv)
       continue;
     if(ph.memsz < ph.filesz)
       goto bad;
-    if (!allocuvm(pgdir, (char *)ph.va, ph.memsz))
+    if(!allocuvm(pgdir, (char *)ph.va, ph.memsz))
       goto bad;
     if(ph.va + ph.memsz > sz)
       sz = ph.va + ph.memsz;
-    if (!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz))
+    if(!loaduvm(pgdir, (char *)ph.va, ip, ph.offset, ph.filesz))
       goto bad;
   }
   iunlockput(ip);
@@ -53,7 +53,7 @@ exec(char *path, char **argv)
   // Allocate and initialize stack at sz
   sz = PGROUNDUP(sz);
   sz += PGSIZE; // leave an invalid page
-  if (!allocuvm(pgdir, (char *)sz, PGSIZE))
+  if(!allocuvm(pgdir, (char *)sz, PGSIZE))
     goto bad;
   mem = uva2ka(pgdir, (char *)sz);
   spoffset = sz;
@@ -105,7 +105,7 @@ exec(char *path, char **argv)
   return 0;
 
  bad:
-  if (pgdir) freevm(pgdir);
+  if(pgdir) freevm(pgdir);
   iunlockput(ip);
   return -1;
 }
diff --git a/trap.c b/trap.c
index ae26739..b2b2ebb 100644
--- a/trap.c
+++ b/trap.c
@@ -86,7 +86,7 @@ trap(struct trapframe *tf)
     cprintf("pid %d %s: trap %d err %d on cpu %d "
             "eip 0x%x addr 0x%x--kill proc\n",
             proc->pid, proc->name, tf->trapno, tf->err, cpu->id, tf->eip, 
-	    rcr2());
+            rcr2());
     proc->killed = 1;
   }
 
diff --git a/vm.c b/vm.c
index a60c915..c3601a4 100644
--- a/vm.c
+++ b/vm.c
@@ -244,13 +244,13 @@ freevm(pde_t *pgdir)
     if (da != 0) {
       pte_t *pgtab = (pte_t*) da;
       for (j = 0; j < NPTENTRIES; j++) {
-	if (pgtab[j] != 0) {
-	  uint pa = PTE_ADDR(pgtab[j]);
-	  uint va = PGADDR(i, j, 0);
-	  if (va < USERTOP)   // user memory
+        if (pgtab[j] != 0) {
+          uint pa = PTE_ADDR(pgtab[j]);
+          uint va = PGADDR(i, j, 0);
+          if (va < USERTOP)   // user memory
             kfree((void *) pa);
-	  pgtab[j] = 0;
-	}
+          pgtab[j] = 0;
+        }
       }
       kfree((void *) da);
       pgdir[i] = 0;
@@ -287,7 +287,7 @@ inituvm(pde_t *pgdir, char *addr, char *init, uint sz)
 
   for (i = 0; i < sz; i += PGSIZE) {
     if (!(pte = walkpgdir(pgdir, (void *)(i+addr), 0)))
-	panic("inituvm: pte should exist\n");
+      panic("inituvm: pte should exist\n");
     off = (i+(uint)addr) % PGSIZE;
     pa = PTE_ADDR(*pte);
     if (sz - i < PGSIZE) n = sz - i;