diff --git a/chapter4_memory.md b/chapter4_memory.md
index 3045555..87f988d 100644
--- a/chapter4_memory.md
+++ b/chapter4_memory.md
@@ -1191,15 +1191,15 @@ hartid = 0: vaddr 0x00404000 is mapped to paddr 0x87f9a000
 === user alloc 0 @ vaddr 0x00404000
 hartid = 1: alloc page 0x87f99000
 hartid = 1: vaddr 0x00404000 is mapped to paddr 0x87f99000
-=== user0: 0
+=== user 0: 0
 >>> user alloc 1 @ vaddr 0x00404000
-=== user0: 1
+=== user 0: 1
 >>> user 1: 5
-=== user0: 2
+=== user 0: 2
 >>> user 1: 6
-=== user0: 3
+=== user 0: 3
 >>> user 1: 7
-=== user0: 4
+=== user 0: 4
 >>> user 1: 8
 hartid = 0: User exit with code: 0.
 >>> user 1: 9