diff --git a/apps/crt0.S b/apps/crt0.S
index 7ef9e65..d73c0ea 100644
--- a/apps/crt0.S
+++ b/apps/crt0.S
@@ -7,8 +7,11 @@ _start:
 sw	ra,12(sp)
 jal	ra, main
 #if 1
+// rust will interpret the "#if 1" and "#include" as comments and ignore
+// C, asm, zig will include the file below, which references a constant from uvm32_sys.h
 #include "non-rust-crt0-hack.S"
 #else
+// only rust will see this
 li a7, {IOREQ_HALT}
 #endif
 ecall