diff --git a/fat.asm b/fat.asm
index 4e99781..0416842 100644
--- a/fat.asm
+++ b/fat.asm
@@ -16,6 +16,7 @@ cclus:	dw 0
 csec:	dw 0
 
 	times (0x0B - ($-$$)) db 0
+	; BIOS PARAMETER BLOCK
 fdc:	; sector size
 .ss:	dw 0x200
 	; sectors per cluster
@@ -38,6 +39,7 @@ fdc:	; sector size
 
 	; mformat keeps writing until here
 	; if we place init earlier, code gets overwritten
+	; this also marks the end for the BPB
 	times (62 - ($-$$)) nop
 
 init:	xor ax, ax
diff --git a/fix-rom.c b/fix-rom.c
index d1099ed..b94574e 100644
--- a/fix-rom.c
+++ b/fix-rom.c
@@ -1,3 +1,8 @@
+/* QEMU and x86 hardware with PCI support (and up) require that BIOS options
+ * rom have a valid checksum, that the sum of all their bytes equals zero.
+ * This script edits a rom binary in-place so it fits that criteria.
+ */
+
 #include <stdio.h>
 #include <sys/types.h>
 #include <sys/stat.h>
diff --git a/hello.asm b/hello.asm
index 9a41dfe..30c954c 100644
--- a/hello.asm
+++ b/hello.asm
@@ -1,4 +1,5 @@
 ; COM program displaying hello world string
+; This is primarily for testing purposes
 org 0x0100
 
 main: