diff --git a/mmu.h b/mmu.h
index 48a3787..c8b45fc 100644
--- a/mmu.h
+++ b/mmu.h
@@ -15,12 +15,12 @@
 
 // Segment selectors (indexes) in our GDTs.
 // Defined by our convention, not the architecture.
-#define KCSEG32 (1<<3)  /* kernel 32-bit code segment */
-#define KCSEG   (2<<3)  /* kernel code segment */
-#define KDSEG   (3<<3)  /* kernel data segment */
-#define TSSSEG  (4<<3)  /* tss segment - takes two slots */
-#define UDSEG   (6<<3)  /* user data segment */
-#define UCSEG   (7<<3)  /* user code segment */
+#define SEG_KCODE32 (1<<3)  // kernel 32-bit code segment
+#define SEG_KCODE   (2<<3)  // kernel code segment
+#define SEG_KDATA   (3<<3)  // kernel data segment
+#define SEG_TSS     (4<<3)  // tss segment - takes two slots
+#define SEG_UDATA   (6<<3)  // user data segment
+#define SEG_UCODE   (7<<3)  // user code segment
 
 #define NSEGS 8
 
@@ -54,21 +54,21 @@ struct segdesc {
 
 #define DPL_USER    0x3     // User DPL
 
-#define SEG_A      (1<<0)      /* segment accessed bit */
-#define SEG_R      (1<<1)      /* readable (code) */
-#define SEG_W      (1<<1)      /* writable (data) */
-#define SEG_C      (1<<2)      /* conforming segment (code) */
-#define SEG_E      (1<<2)      /* expand-down bit (data) */
-#define SEG_CODE   (1<<3)      /* code segment (instead of data) */
+#define SEG_A      (1<<0)      // segment accessed bit 
+#define SEG_R      (1<<1)      // readable (code) 
+#define SEG_W      (1<<1)      // writable (data) 
+#define SEG_C      (1<<2)      // conforming segment (code) 
+#define SEG_E      (1<<2)      // expand-down bit (data) 
+#define SEG_CODE   (1<<3)      // code segment (instead of data) 
 
 // User and system segment bits.
-#define SEG_S      (1<<4)      /* if 0, system descriptor */
-#define SEG_DPL(x) ((x)<<5)    /* descriptor privilege level (2 bits) */
-#define SEG_P      (1<<7)      /* segment present */
-#define SEG_AVL    (1<<8)      /* available for operating system use */
-#define SEG_L      (1<<9)      /* long mode */
-#define SEG_D      (1<<10)     /* default operation size 32-bit */
-#define SEG_G      (1<<11)     /* granularity */
+#define SEG_S      (1<<4)      // if 0, system descriptor 
+#define SEG_DPL(x) ((x)<<5)    // descriptor privilege level (2 bits) 
+#define SEG_P      (1<<7)      // segment present 
+#define SEG_AVL    (1<<8)      // available for operating system use 
+#define SEG_L      (1<<9)      // long mode 
+#define SEG_D      (1<<10)     // default operation size 32-bit 
+#define SEG_G      (1<<11)     // granularity 
 
 // Application segment type bits
 #define STA_X       0x8     // Executable segment
@@ -76,12 +76,12 @@ struct segdesc {
 #define STA_R       0x2     // Readable (executable segments)
 
 // System segment type bits
-#define SEG_LDT    (2<<0)      /* local descriptor table */
-#define SEG_TSS64A (9<<0)      /* available 64-bit TSS */
-#define SEG_TSS64B (11<<0)     /* busy 64-bit TSS */
-#define SEG_CALL64 (12<<0)     /* 64-bit call gate */
-#define SEG_INTR64 (14<<0)     /* 64-bit interrupt gate */
-#define SEG_TRAP64 (15<<0)     /* 64-bit trap gate */
+#define SEG_LDT    (2<<0)      // local descriptor table 
+#define SEG_TSS64A (9<<0)      // available 64-bit TSS 
+#define SEG_TSS64B (11<<0)     // busy 64-bit TSS 
+#define SEG_CALL64 (12<<0)     // 64-bit call gate 
+#define SEG_INTR64 (14<<0)     // 64-bit interrupt gate 
+#define SEG_TRAP64 (15<<0)     // 64-bit trap gate 
 
 // A virtual address 'la' has a six-part structure as follows:
 //
@@ -129,7 +129,7 @@ struct taskstate {
   uint8 iopb[0];
 } __attribute__ ((packed));
 
-#define INT_P      (1<<7)      /* interrupt descriptor present */
+#define INT_P      (1<<7)      // interrupt descriptor present
 
 struct intgate
 {
diff --git a/proc.c b/proc.c
index 4d0faec..14c3da8 100644
--- a/proc.c
+++ b/proc.c
@@ -139,8 +139,8 @@ userinit(void)
   inituvm(p->pgdir, _binary_initcode_start, (uint64)_binary_initcode_size);
   p->sz = PGSIZE;
   memset(p->tf, 0, sizeof(*p->tf));
-  p->tf->cs = UCSEG | 0x3;
-  p->tf->ss = UDSEG | 0x3;
+  p->tf->cs = SEG_UCODE | DPL_USER;
+  p->tf->ss = SEG_UDATA | DPL_USER;
   p->tf->r11 = FL_IF;
   p->tf->rsp = PGSIZE;
   p->tf->rcx = 0;  // beginning of initcode.S
diff --git a/trap.c b/trap.c
index c6c6bc2..afa0e18 100644
--- a/trap.c
+++ b/trap.c
@@ -20,7 +20,7 @@ tvinit(void)
   int i;
 
   for(i=0; i<256; i++) {
-    idt[i] = INTDESC(KCSEG, vectors[i], INT_P | SEG_INTR64);
+    idt[i] = INTDESC(SEG_KCODE, vectors[i], INT_P | SEG_INTR64);
   }
   idtinit();
     
diff --git a/vm.c b/vm.c
index e992ed4..4b272ff 100644
--- a/vm.c
+++ b/vm.c
@@ -49,13 +49,13 @@ seginit(void)
   // to (star >> 32) + 8 and the CS selector to (star >> 32).
   // When executing a sysret instruction the CPU sets the SS selector
   // to (star >> 48) + 8 and the CS selector to (star >> 48) + 16.
-  uint64 star = ((((uint64)UCSEG|0x3)- 16)<<48)|((uint64)(KCSEG)<<32);
+  uint64 star = ((((uint64)SEG_UCODE|0x3)- 16)<<48)|((uint64)(SEG_KCODE)<<32);
   writemsr(MSR_STAR, star);
   writemsr(MSR_LSTAR, (uint64)&sysentry);
   writemsr(MSR_SFMASK, FL_TF | FL_IF);
 
     // Initialize cpu-local storage.
-  writegs(KDSEG);
+  writegs(SEG_KDATA);
   writemsr(MSR_GS_BASE, (uint64)c);
   writemsr(MSR_GS_KERNBASE, (uint64)c);
 }
@@ -202,8 +202,8 @@ switchuvm(struct proc *p)
 
   c = mycpu();
   uint64 base = (uint64) &(c->ts);
-  c->gdt[TSSSEG>>3] =  SEGDESC(base, (sizeof(c->ts)-1), SEG_P|SEG_TSS64A);
-  c->gdt[(TSSSEG>>3)+1] = SEGDESCHI(base);
+  c->gdt[SEG_TSS>>3] =  SEGDESC(base, (sizeof(c->ts)-1), SEG_P|SEG_TSS64A);
+  c->gdt[(SEG_TSS>>3)+1] = SEGDESCHI(base);
   c->ts.rsp[0] = (uint64) p->kstack + KSTACKSIZE;
   c->ts.iomba = (ushort) 0xFFFF;
 
@@ -211,7 +211,7 @@ switchuvm(struct proc *p)
   dtr.base = (uint64)c->gdt;
   lgdt((void *)&dtr.limit);
 
-  ltr(TSSSEG);
+  ltr(SEG_TSS);
 
   lcr3(V2P(p->pgdir));  // switch to process's address space