diff --git a/eBook/12.2.md b/eBook/12.2.md
index 163bfd0..b5c4322 100644
--- a/eBook/12.2.md
+++ b/eBook/12.2.md
@@ -71,7 +71,7 @@ func main() {
         // panic(err.Error())
         }
     fmt.Printf("%s\n", string(buf))
-    err = ioutil.WriteFile(outputFile, buf, 0x644)
+    err = ioutil.WriteFile(outputFile, buf, 0644) // oct, not hex
     if err != nil {
         panic(err. Error())
     }
diff --git a/eBook/examples/chapter_12/read_write_file1.go b/eBook/examples/chapter_12/read_write_file1.go
index 57314a5..b6138a7 100644
--- a/eBook/examples/chapter_12/read_write_file1.go
+++ b/eBook/examples/chapter_12/read_write_file1.go
@@ -14,7 +14,7 @@ func main() {
 		panic(err.Error())
 	}
 	fmt.Printf("%s\n", string(buf))
-	err = ioutil.WriteFile(outputFile, buf, 0x644)
+	err = ioutil.WriteFile(outputFile, buf, 0644) // oct, not hex
 	if err != nil {
 		panic(err.Error())
 	}