diff --git a/kernel/memlayout.h b/kernel/memlayout.h
index b6e595d..776f98c 100644
--- a/kernel/memlayout.h
+++ b/kernel/memlayout.h
@@ -25,12 +25,12 @@
 #define VIRTIO0 0x10001000
 #define VIRTIO0_IRQ 1
 
-// local interrupt controller, which contains the timer.
+// core local interruptor (CLINT), which contains the timer.
 #define CLINT 0x2000000L
 #define CLINT_MTIMECMP(hartid) (CLINT + 0x4000 + 8*(hartid))
 #define CLINT_MTIME (CLINT + 0xBFF8) // cycles since boot.
 
-// qemu puts programmable interrupt controller here.
+// qemu puts platform-level interrupt controller (PLIC) here.
 #define PLIC 0x0c000000L
 #define PLIC_PRIORITY (PLIC + 0x0)
 #define PLIC_PENDING (PLIC + 0x1000)