diff --git a/kill.c b/kill.c
index 2d69d4d..5e60113 100644
--- a/kill.c
+++ b/kill.c
@@ -6,7 +6,7 @@ int
 main(int argc, char **argv)
 {
   int i;
-	
+
   if(argc < 1){
     printf(2, "usage: kill pid...\n");
     exit();
diff --git a/lapic.c b/lapic.c
index f64f54b..19c5b4b 100644
--- a/lapic.c
+++ b/lapic.c
@@ -156,7 +156,7 @@ lapicstartap(uchar apicid, uint addr)
   lapicw(ICRLO, INIT | LEVEL | ASSERT);
   microdelay(200);
   lapicw(ICRLO, INIT | LEVEL);
-  microdelay(100);	// should be 10ms, but too slow in Bochs!
+  microdelay(100);    // should be 10ms, but too slow in Bochs!
   
   // Send startup IPI (twice!) to enter bootstrap code.
   // Regular hardware is supposed to only accept a STARTUP
diff --git a/proc.h b/proc.h
index eebfa23..d37975c 100644
--- a/proc.h
+++ b/proc.h
@@ -32,7 +32,7 @@ struct proc {
   uint sz;                     // Size of process memory (bytes)
   char *kstack;                // Bottom of kernel stack for this process
   enum proc_state state;       // Process state
-  int pid;                     // Process ID
+  volatile int pid;            // Process ID
   struct proc *parent;         // Parent process
   struct trapframe *tf;        // Trap frame for current syscall
   struct context *context;     // Switch here to run process
diff --git a/uart.c b/uart.c
index 298066f..4cd1e0f 100644
--- a/uart.c
+++ b/uart.c
@@ -10,67 +10,67 @@
 #include "proc.h"
 #include "x86.h"
 
-#define COM1	0x3f8
+#define COM1    0x3f8
 
-static int uart;	// is there a uart?
+static int uart;    // is there a uart?
 
 void
 uartinit(void)
 {
-	char *p;
+  char *p;
 
-	// Turn off the FIFO
-	outb(COM1+2, 0);
-	
-	// 9600 baud, 8 data bits, 1 stop bit, parity off.
-	outb(COM1+3, 0x80);	// Unlock divisor
-	outb(COM1+0, 115200/9600);
-	outb(COM1+1, 0);
-	outb(COM1+3, 0x03);	// Lock divisor, 8 data bits.
-	outb(COM1+4, 0);
-	outb(COM1+1, 0x01);	// Enable receive interrupts.
+  // Turn off the FIFO
+  outb(COM1+2, 0);
+  
+  // 9600 baud, 8 data bits, 1 stop bit, parity off.
+  outb(COM1+3, 0x80);    // Unlock divisor
+  outb(COM1+0, 115200/9600);
+  outb(COM1+1, 0);
+  outb(COM1+3, 0x03);    // Lock divisor, 8 data bits.
+  outb(COM1+4, 0);
+  outb(COM1+1, 0x01);    // Enable receive interrupts.
 
-	// If status is 0xFF, no serial port.
-	if(inb(COM1+5) == 0xFF)
-		return;
-	uart = 1;
+  // If status is 0xFF, no serial port.
+  if(inb(COM1+5) == 0xFF)
+    return;
+  uart = 1;
 
-	// Acknowledge pre-existing interrupt conditions;
-	// enable interrupts.
-	inb(COM1+2);
-	inb(COM1+0);
-	picenable(IRQ_COM1);
-	ioapicenable(IRQ_COM1, 0);
-	
-	// Announce that we're here.
-	for(p="xv6...\n"; *p; p++)
-		uartputc(*p);
+  // Acknowledge pre-existing interrupt conditions;
+  // enable interrupts.
+  inb(COM1+2);
+  inb(COM1+0);
+  picenable(IRQ_COM1);
+  ioapicenable(IRQ_COM1, 0);
+  
+  // Announce that we're here.
+  for(p="xv6...\n"; *p; p++)
+    uartputc(*p);
 }
 
 void
 uartputc(int c)
 {
-	int i;
+  int i;
 
-	if(!uart)
-		return;
-	for(i = 0; i < 128 && !(inb(COM1+5) & 0x20); i++)
-		microdelay(10);
-	outb(COM1+0, c);
+  if(!uart)
+    return;
+  for(i = 0; i < 128 && !(inb(COM1+5) & 0x20); i++)
+    microdelay(10);
+  outb(COM1+0, c);
 }
 
 static int
 uartgetc(void)
 {
-	if(!uart)
-		return -1;
-	if(!(inb(COM1+5) & 0x01))
-		return -1;
-	return inb(COM1+0);
+  if(!uart)
+    return -1;
+  if(!(inb(COM1+5) & 0x01))
+    return -1;
+  return inb(COM1+0);
 }
 
 void
 uartintr(void)
 {
-	consoleintr(uartgetc);
+  consoleintr(uartgetc);
 }