diff --git a/include/ucore/atomic.h b/include/ucore/atomic.h
index 1d7184d..5311352 100644
--- a/include/ucore/atomic.h
+++ b/include/ucore/atomic.h
@@ -1,8 +1,12 @@
 #ifndef UC_ATOMIC_H_
 #define UC_ATOMIC_H_
 
-#ifdef __GNUC__
+/** Atomic functions (macros). The ptr argument must be a pointer to 
+ * an integer type.
+ * For gcc, see http://gcc.gnu.org/onlinedocs/gcc-4.8.1/gcc/_005f_005fsync-Builtins.html
+ */
 
+#ifdef __GNUC__
 
 /**
  * Atomically add val to *ptr
@@ -11,7 +15,7 @@
 #define UC_ATOMIC_ADD(ptr, val) __sync_fetch_and_add((ptr), (val))
 
 /**
- * Atomically subtract val to *ptr
+ * Atomically subtract val from *ptr
  * @return *ptr before the subtraction
  */
 #define UC_ATOMIC_SUB(ptr, val) __sync_fetch_and_add((ptr), -(val))
@@ -30,8 +34,7 @@
 
 
 /**
- * UC_ATOMIC_CAS(p, 12, 
- * Compare-And-Swap. If *ptr is oldval, write newwal to *ptr. 
+ * Atomic Compare-And-Swap. If *ptr is oldval, write newwal to *ptr. 
  * @return *ptr that was before the operation.
  */
 #define UC_ATOMIC_CAS(ptr, oldval, newval) __sync_val_compare_and_swap((ptr), (oldval), (newval))