diff --git a/main.c b/main.c
index 76e9eeb..10a448e 100644
--- a/main.c
+++ b/main.c
@@ -118,13 +118,13 @@ mpmain(void)
 void
 process0(void)
 {
-  struct proc *p0 = &proc[0];
-  struct proc *p1;
   extern struct spinlock proc_table_lock;
+  struct proc *p0, *p1;
   struct trapframe tf;
 
   release(&proc_table_lock);
 
+  p0 = &proc[0];
   p0->cwd = iget(rootdev, 1);
   iunlock(p0->cwd);
 
diff --git a/printf.c b/printf.c
index e013346..0ddd90b 100644
--- a/printf.c
+++ b/printf.c
@@ -11,18 +11,20 @@ putc(int fd, char c)
 static void
 printint(int fd, int xx, int base, int sgn)
 {
+  static char digits[] = "0123456789ABCDEF";
   char buf[16];
-  char digits[] = "0123456789ABCDEF";
-  int i = 0, neg = 0;
+  int i, neg;
   uint x;
 
+  neg = 0;
   if(sgn && xx < 0){
     neg = 1;
-    x = 0 - xx;
+    x = -xx;
   } else {
     x = xx;
   }
 
+  i = 0;
   do {
     buf[i++] = digits[x % base];
   } while((x /= base) != 0);
@@ -37,9 +39,12 @@ printint(int fd, int xx, int base, int sgn)
 void
 printf(int fd, char *fmt, ...)
 {
-  int i, state = 0, c;
-  uint *ap = (uint*)(void*)&fmt + 1;
+  char *s;
+  int c, i, state;
+  uint *ap;
 
+  state = 0;
+  ap = (uint*)(void*)&fmt + 1;
   for(i = 0; fmt[i]; i++){
     c = fmt[i] & 0xff;
     if(state == 0){
@@ -56,7 +61,7 @@ printf(int fd, char *fmt, ...)
         printint(fd, *ap, 16, 0);
         ap++;
       } else if(c == 's'){
-        char *s = (char*)*ap;
+        s = (char*)*ap;
         ap++;
         while(*s != 0){
           putc(fd, *s);
diff --git a/string.c b/string.c
index dc73266..a871b68 100644
--- a/string.c
+++ b/string.c
@@ -4,8 +4,9 @@
 void*
 memset(void *dst, int c, uint n)
 {
-  char *d = (char*) dst;
+  char *d;
 
+  d = (char*)dst;
   while(n-- > 0)
     *d++ = c;
 
@@ -15,12 +16,13 @@ memset(void *dst, int c, uint n)
 int
 memcmp(const void *v1, const void *v2, uint n)
 {
-  const uchar *s1 = (const uchar*) v1;
-  const uchar *s2 = (const uchar*) v2;
-
+  const uchar *s1, *s2;
+  
+  s1 = v1;
+  s2 = v2;
   while(n-- > 0) {
     if(*s1 != *s2)
-      return (int) *s1 - (int) *s2;
+      return *s1 - *s2;
     s1++, s2++;
   }
 
diff --git a/sysfile.c b/sysfile.c
index a73f250..e5d4eae 100644
--- a/sysfile.c
+++ b/sysfile.c
@@ -54,7 +54,7 @@ int
 sys_pipe(void)
 {
   int *fd;
-  struct file *rf = 0, *wf = 0;
+  struct file *rf, *wf;
   int fd0, fd1;
 
   if(argptr(0, (void*)&fd, 2*sizeof fd[0]) < 0)
diff --git a/trap.c b/trap.c
index 7a47516..ed66e99 100644
--- a/trap.c
+++ b/trap.c
@@ -30,9 +30,7 @@ idtinit(void)
 void
 trap(struct trapframe *tf)
 {
-  int v = tf->trapno;
-
-  if(v == T_SYSCALL){
+  if(tf->trapno == T_SYSCALL){
     if(cp->killed)
       proc_exit();
     cp->tf = tf;
@@ -47,7 +45,7 @@ trap(struct trapframe *tf)
   // during interrupt handler.  Decrement before returning.
   cpus[cpu()].nlock++;
 
-  switch(v){
+  switch(tf->trapno){
   case IRQ_OFFSET + IRQ_TIMER:
     lapic_timerintr();
     cpus[cpu()].nlock--;
@@ -82,12 +80,13 @@ trap(struct trapframe *tf)
     if(cp) {
       // Assume process divided by zero or dereferenced null, etc.
       cprintf("pid %d %s: unhandled trap %d on cpu %d eip %x -- kill proc\n",
-              cp->pid, cp->name, v, cpu(), tf->eip);
+              cp->pid, cp->name, tf->trapno, cpu(), tf->eip);
       proc_exit();
     }
     
     // Otherwise it's our mistake.
-    cprintf("unexpected trap %d from cpu %d eip %x\n", v, cpu(), tf->eip);
+    cprintf("unexpected trap %d from cpu %d eip %x\n",
+            tf->trapno, cpu(), tf->eip);
     panic("trap");
   }
   
diff --git a/ulib.c b/ulib.c
index 994ceb9..6c57b2d 100644
--- a/ulib.c
+++ b/ulib.c
@@ -31,7 +31,8 @@ strcmp(const char *p, const char *q)
 uint
 strlen(char *s)
 {
-  int n = 0;
+  int n;
+
   for(n = 0; s[n]; n++)
     ;
   return n;
@@ -40,11 +41,11 @@ strlen(char *s)
 void*
 memset(void *dst, int c, uint n)
 {
-  char *d = (char*) dst;
-
+  char *d;
+  
+  d = dst;
   while(n-- > 0)
     *d++ = c;
-
   return dst;
 }
 
@@ -60,10 +61,10 @@ strchr(const char *s, char c)
 char*
 gets(char *buf, int max)
 {
-  int i = 0, cc;
+  int i, cc;
   char c;
 
-  while(i+1 < max){
+  for(i=0; i+1 < max; ){
     cc = read(0, &c, 1);
     if(cc < 1)
       break;
diff --git a/umalloc.c b/umalloc.c
index 3473c79..30f970d 100644
--- a/umalloc.c
+++ b/umalloc.c
@@ -19,7 +19,7 @@ union header {
 typedef union header Header;
 
 static Header base;
-static Header *freep = 0;
+static Header *freep;
 
 void
 free(void *ap)
diff --git a/usertests.c b/usertests.c
index 30673c3..a449ed0 100644
--- a/usertests.c
+++ b/usertests.c
@@ -203,13 +203,14 @@ void
 pipe1(void)
 {
   int fds[2], pid;
-  int seq = 0, i, n, cc, total;
+  int seq, i, n, cc, total;
 
   if(pipe(fds) != 0){
     printf(1, "pipe() failed\n");
     exit();
   }
   pid = fork();
+  seq = 0;
   if(pid == 0){
     close(fds[0]);
     for(n = 0; n < 5; n++){
@@ -464,8 +465,8 @@ twofiles(void)
 void
 createdelete(void)
 {
+  enum { N = 20 };
   int pid, i, fd;
-  int n = 20;
   char name[32];
 
   printf(1, "createdelete test\n");
@@ -477,7 +478,7 @@ createdelete(void)
 
   name[0] = pid ? 'p' : 'c';
   name[2] = '\0';
-  for(i = 0; i < n; i++){
+  for(i = 0; i < N; i++){
     name[1] = '0' + i;
     fd = open(name, O_CREATE | O_RDWR);
     if(fd < 0){
@@ -499,14 +500,14 @@ createdelete(void)
   //  else
   //exit();
 
-  for(i = 0; i < n; i++){
+  for(i = 0; i < N; i++){
     name[0] = 'p';
     name[1] = '0' + i;
     fd = open(name, 0);
-    if((i == 0 || i >= n/2) && fd < 0){
+    if((i == 0 || i >= N/2) && fd < 0){
       printf(1, "oops createdelete %s didn't exist\n", name);
       exit();
-    } else if((i >= 1 && i < n/2) && fd >= 0){
+    } else if((i >= 1 && i < N/2) && fd >= 0){
       printf(1, "oops createdelete %s did exist\n", name);
       exit();
     }
@@ -516,10 +517,10 @@ createdelete(void)
     name[0] = 'c';
     name[1] = '0' + i;
     fd = open(name, 0);
-    if((i == 0 || i >= n/2) && fd < 0){
+    if((i == 0 || i >= N/2) && fd < 0){
       printf(1, "oops createdelete %s didn't exist\n", name);
       exit();
-    } else if((i >= 1 && i < n/2) && fd >= 0){
+    } else if((i >= 1 && i < N/2) && fd >= 0){
       printf(1, "oops createdelete %s did exist\n", name);
       exit();
     }
@@ -527,7 +528,7 @@ createdelete(void)
       close(fd);
   }
 
-  for(i = 0; i < n; i++){
+  for(i = 0; i < N; i++){
     name[0] = 'p';
     name[1] = '0' + i;
     unlink(name);