diff --git a/android-project/jni/src/Android.mk b/android-project/jni/src/Android.mk
index 3e0942fe..67c1f534 100644
--- a/android-project/jni/src/Android.mk
+++ b/android-project/jni/src/Android.mk
@@ -12,7 +12,6 @@ NP2_PATH := $(LOCAL_PATH)/../np2
 LOCAL_C_INCLUDES := $(LOCAL_PATH)/$(SDL_PATH)/include \
 	$(LOCAL_PATH) \
 	$(NP2_PATH) \
-	$(NP2_PATH)/bios \
 	$(NP2_PATH)/cbus \
 	$(NP2_PATH)/common \
 	$(NP2_PATH)/embed \
@@ -23,7 +22,6 @@ LOCAL_C_INCLUDES := $(LOCAL_PATH)/$(SDL_PATH)/include \
 	$(NP2_PATH)/generic \
 	$(NP2_PATH)/i286c \
 	$(NP2_PATH)/io \
-	$(NP2_PATH)/lio \
 	$(NP2_PATH)/mem \
 	$(NP2_PATH)/sdl2 \
 	$(NP2_PATH)/sound \
diff --git a/bios/bios.c b/bios/bios.c
index ac0c0d6f..93923375 100644
--- a/bios/bios.c
+++ b/bios/bios.c
@@ -1,21 +1,26 @@
-#include	"compiler.h"
-#include	"strres.h"
-#include	"dosio.h"
-#include	"cpucore.h"
-#include	"pccore.h"
-#include	"iocore.h"
-#include	"bios.h"
-#include	"biosmem.h"
-#include	"sxsibios.h"
-#include	"lio.h"
-#include	"vram.h"
-#include	"fddfile.h"
-#include	"fdd_mtr.h"
-#include	"fdfmt.h"
-#include	"keytable.res"
-#include	"itfrom.res"
-#include	"startup.res"
-#include	"biosfd80.res"
+/**
+ * @file	bios.c
+ * @brief	Implementation of BIOS
+ */
+
+#include "compiler.h"
+#include "bios.h"
+#include "biosmem.h"
+#include "sxsibios.h"
+#include "strres.h"
+#include "cpucore.h"
+#include "pccore.h"
+#include "iocore.h"
+#include "lio/lio.h"
+#include "vram.h"
+#include "fddfile.h"
+#include "fdd_mtr.h"
+#include "fdfmt.h"
+#include "dosio.h"
+#include "keytable.res"
+#include "itfrom.res"
+#include "startup.res"
+#include "biosfd80.res"
 
 
 #define	BIOS_SIMULATE
diff --git a/bios/bios.h b/bios/bios.h
index eb7a651b..1b8409c0 100644
--- a/bios/bios.h
+++ b/bios/bios.h
@@ -1,3 +1,11 @@
+/**
+ * @file	bios.h
+ * @brief	Interface of BIOS
+ */
+
+#pragma once
+
+#include "cpumem.h"
 
 enum {
 	BIOS_SEG		= 0xfd80,
diff --git a/bios/biosmem.h b/bios/biosmem.h
index 2060da16..e4f83c30 100644
--- a/bios/biosmem.h
+++ b/bios/biosmem.h
@@ -1,3 +1,9 @@
+/**
+ * @file	biosmem.h
+ * @brief	Defines of BIOS memory
+ */
+
+#pragma once
 
 enum {
 	MEMB_EXPMMSZ			= 0x00401,
diff --git a/bios/sxsibios.c b/bios/sxsibios.c
index 7c00269e..25fd5300 100644
--- a/bios/sxsibios.c
+++ b/bios/sxsibios.c
@@ -1,9 +1,13 @@
-#include	"compiler.h"
+/**
+ * @file	sxsibios.c
+ * @brief	Implementation of SxSI BIOS
+ */
+
+#include "compiler.h"
+#include "sxsibios.h"
+#include "biosmem.h"
 #include	"cpucore.h"
 #include	"pccore.h"
-#include	"bios.h"
-#include	"biosmem.h"
-#include	"sxsibios.h"
 #include	"scsicmd.h"
 #include	"sxsi.h"
 #include	"timing.h"
diff --git a/bios/sxsibios.h b/bios/sxsibios.h
index 8ad8f745..09131546 100644
--- a/bios/sxsibios.h
+++ b/bios/sxsibios.h
@@ -1,3 +1,9 @@
+/**
+ * @file	sxsibios.h
+ * @brief	Interface of SxSI BIOS
+ */
+
+#pragma once
 
 enum {
 	SXSIBIOS_SASI		= 0,
@@ -27,4 +33,3 @@ void np2sysp_scsidev(const void *arg1, long arg2);
 #ifdef __cplusplus
 }
 #endif
-
diff --git a/i286c/cpumem.h b/i286c/cpumem.h
index 8bbeac0c..2fc08da4 100644
--- a/i286c/cpumem.h
+++ b/i286c/cpumem.h
@@ -1,4 +1,6 @@
 
+#pragma once
+
 #ifndef MEMCALL
 #define	MEMCALL
 #endif
diff --git a/i286c/i286c_mn.c b/i286c/i286c_mn.c
index df3557ee..95799bbe 100644
--- a/i286c/i286c_mn.c
+++ b/i286c/i286c_mn.c
@@ -3,7 +3,7 @@
 #include	"i286c.h"
 #include	"pccore.h"
 #include	"iocore.h"
-#include	"bios.h"
+#include	"bios/bios.h"
 #include	"i286c.mcr"
 #if defined(ENABLE_TRAP)
 #include "trap/inttrap.h"
diff --git a/i286c/v30patch.c b/i286c/v30patch.c
index 21e524a1..4aef7adc 100644
--- a/i286c/v30patch.c
+++ b/i286c/v30patch.c
@@ -4,7 +4,7 @@
 #include	"v30patch.h"
 #include	"pccore.h"
 #include	"iocore.h"
-#include	"bios.h"
+#include	"bios/bios.h"
 #include	"dmav30.h"
 #include	"i286c.mcr"
 #if defined(ENABLE_TRAP)
diff --git a/i286x/cpumem.h b/i286x/cpumem.h
index 8c2225fe..2731ed71 100644
--- a/i286x/cpumem.h
+++ b/i286x/cpumem.h
@@ -1,4 +1,6 @@
 
+#pragma once
+
 #ifndef MEMCALL
 #define	MEMCALL
 #endif
diff --git a/i286x/i286x.cpp b/i286x/i286x.cpp
index 3e4feb4d..4e82bc42 100644
--- a/i286x/i286x.cpp
+++ b/i286x/i286x.cpp
@@ -10,7 +10,7 @@
 #include	"i286x.mcr"
 #include	"i286xea.mcr"
 #include	"v30patch.h"
-#include	"bios.h"
+#include	"bios/bios.h"
 #include	"dmax86.h"
 #if defined(ENABLE_TRAP)
 #include "trap/inttrap.h"
diff --git a/i286x/v30patch.cpp b/i286x/v30patch.cpp
index 03e83c4a..75113b4a 100644
--- a/i286x/v30patch.cpp
+++ b/i286x/v30patch.cpp
@@ -6,7 +6,7 @@
 #include	"i286xrep.h"
 #include	"i286xcts.h"
 #include	"pccore.h"
-#include	"bios.h"
+#include	"bios/bios.h"
 #include	"iocore.h"
 #include	"i286x.mcr"
 #include	"i286xea.mcr"
diff --git a/i386c/ia32/interface.c b/i386c/ia32/interface.c
index 68b6a20d..8a21c433 100644
--- a/i386c/ia32/interface.c
+++ b/i386c/ia32/interface.c
@@ -33,7 +33,7 @@
 #include "pccore.h"
 #include "iocore.h"
 #include "dmax86.h"
-#include "bios.h"
+#include "bios/bios.h"
 #include "break.h"
 
 
diff --git a/io/np2sysp.c b/io/np2sysp.c
index 63d5f2ea..f3fc2540 100644
--- a/io/np2sysp.c
+++ b/io/np2sysp.c
@@ -7,7 +7,7 @@
 #include	"cpucore.h"
 #include	"pccore.h"
 #include	"iocore.h"
-#include	"sxsibios.h"
+#include	"bios/sxsibios.h"
 #if defined(SUPPORT_HOSTDRV)
 #include	"hostdrv.h"
 #endif
diff --git a/lio/gput1.c b/lio/gput1.c
index 1ce2bcc2..14f66675 100644
--- a/lio/gput1.c
+++ b/lio/gput1.c
@@ -2,7 +2,7 @@
 #include	"cpucore.h"
 #include	"pccore.h"
 #include	"iocore.h"
-#include	"bios.h"
+#include	"bios/bios.h"
 #include	"lio.h"
 #include	"vram.h"
 
diff --git a/lio/gscreen.c b/lio/gscreen.c
index 7f212ef7..33b6cf83 100644
--- a/lio/gscreen.c
+++ b/lio/gscreen.c
@@ -2,8 +2,8 @@
 #include	"cpucore.h"
 #include	"pccore.h"
 #include	"iocore.h"
-#include	"bios.h"
-#include	"biosmem.h"
+#include	"bios/bios.h"
+#include	"bios/biosmem.h"
 #include	"lio.h"
 #include	"vram.h"
 
diff --git a/lio/lio.c b/lio/lio.c
index dfc70918..cace919c 100644
--- a/lio/lio.c
+++ b/lio/lio.c
@@ -1,14 +1,18 @@
-#include	"compiler.h"
-#include	"cpucore.h"
-#include	"pccore.h"
-#include	"iocore.h"
-#include	"gdc_sub.h"
-#include	"bios.h"
-#include	"biosmem.h"
-#include	"vram.h"
-#include	"lio.h"
-#include	"lio.res"
-
+/**
+ * @file	lio.c
+ * @brief	Implementation of LIO
+ */
+
+#include "compiler.h"
+#include "lio.h"
+#include "cpucore.h"
+#include "pccore.h"
+#include "iocore.h"
+#include "gdc_sub.h"
+#include "bios/bios.h"
+#include "bios/biosmem.h"
+#include "vram.h"
+#include "lio.res"
 
 void lio_initialize(void) {
 
diff --git a/lio/lio.h b/lio/lio.h
index 6e1d7c37..b39c5760 100644
--- a/lio/lio.h
+++ b/lio/lio.h
@@ -1,3 +1,9 @@
+/**
+ * @file	lio.h
+ * @brief	Interface of LIO
+ */
+
+#pragma once
 
 enum {
 	LIO_SEGMENT		= 0xf990,
diff --git a/pccore.c b/pccore.c
index aa5df42b..6873c549 100644
--- a/pccore.c
+++ b/pccore.c
@@ -20,8 +20,8 @@
 #include	"pc9861k.h"
 #include	"mpu98ii.h"
 #include	"amd98.h"
-#include	"bios.h"
-#include	"biosmem.h"
+#include "bios/bios.h"
+#include "bios/biosmem.h"
 #include	"vram.h"
 #include	"scrndraw.h"
 #include	"dispsync.h"
diff --git a/sdl2/MacOSX/np2sdl2.xcodeproj/project.pbxproj b/sdl2/MacOSX/np2sdl2.xcodeproj/project.pbxproj
index 296f1980..05e35d5b 100644
--- a/sdl2/MacOSX/np2sdl2.xcodeproj/project.pbxproj
+++ b/sdl2/MacOSX/np2sdl2.xcodeproj/project.pbxproj
@@ -1735,7 +1735,6 @@
 					./np2sdl2,
 					..,
 					../..,
-					../../bios,
 					../../cbus,
 					../../common,
 					../../embed,
@@ -1746,7 +1745,6 @@
 					../../generic,
 					../../i286c,
 					../../io,
-					../../lio,
 					../../mem,
 					../../sound,
 					../../vram,
@@ -1773,7 +1771,6 @@
 					./np2sdl2,
 					..,
 					../..,
-					../../bios,
 					../../cbus,
 					../../common,
 					../../embed,
@@ -1784,7 +1781,6 @@
 					../../generic,
 					../../i286c,
 					../../io,
-					../../lio,
 					../../mem,
 					../../sound,
 					../../vram,
diff --git a/sdl2/iOS/np2sdl2.xcodeproj/project.pbxproj b/sdl2/iOS/np2sdl2.xcodeproj/project.pbxproj
index 6e8be435..ad1c0d14 100644
--- a/sdl2/iOS/np2sdl2.xcodeproj/project.pbxproj
+++ b/sdl2/iOS/np2sdl2.xcodeproj/project.pbxproj
@@ -1700,7 +1700,6 @@
 					.,
 					..,
 					../..,
-					../../bios,
 					../../cbus,
 					../../common,
 					../../embed,
@@ -1711,7 +1710,6 @@
 					../../generic,
 					../../i286c,
 					../../io,
-					../../lio,
 					../../mem,
 					../../sound,
 					../../vram,
@@ -1741,7 +1739,6 @@
 					.,
 					..,
 					../..,
-					../../bios,
 					../../cbus,
 					../../common,
 					../../embed,
@@ -1752,7 +1749,6 @@
 					../../generic,
 					../../i286c,
 					../../io,
-					../../lio,
 					../../mem,
 					../../sound,
 					../../vram,
diff --git a/sdl2/win32/np2sdl2.vcproj b/sdl2/win32/np2sdl2.vcproj
index 72103eda..b3c8fdfa 100644
--- a/sdl2/win32/np2sdl2.vcproj
+++ b/sdl2/win32/np2sdl2.vcproj
@@ -44,7 +44,7 @@
 			<Tool
 				Name="VCCLCompilerTool"
 				Optimization="0"
-				AdditionalIncludeDirectories="..\;.\;..\..\;..\..\bios;..\..\cbus;..\..\common;..\..\embed;..\..\embed\menu;..\..\embed\menubase;..\..\fdd;..\..\font;..\..\generic;..\..\i286c;..\..\io;..\..\lio;..\..\mem;..\..\sound;..\..\vram;..\..\zlib"
+				AdditionalIncludeDirectories="..\;.\;..\..\;..\..\cbus;..\..\common;..\..\embed;..\..\embed\menu;..\..\embed\menubase;..\..\fdd;..\..\font;..\..\generic;..\..\i286c;..\..\io;..\..\mem;..\..\sound;..\..\vram;..\..\zlib"
 				PreprocessorDefinitions="WIN32;_DEBUG;_CONSOLE"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
@@ -118,7 +118,7 @@
 			<Tool
 				Name="VCCLCompilerTool"
 				Optimization="0"
-				AdditionalIncludeDirectories="..\;.\;..\..\;..\..\bios;..\..\cbus;..\..\common;..\..\embed;..\..\embed\menu;..\..\embed\menubase;..\..\fdd;..\..\font;..\..\generic;..\..\i286c;..\..\io;..\..\lio;..\..\mem;..\..\sound;..\..\vram;..\..\zlib"
+				AdditionalIncludeDirectories="..\;.\;..\..\;..\..\cbus;..\..\common;..\..\embed;..\..\embed\menu;..\..\embed\menubase;..\..\fdd;..\..\font;..\..\generic;..\..\i286c;..\..\io;..\..\mem;..\..\sound;..\..\vram;..\..\zlib"
 				PreprocessorDefinitions="WIN32;_DEBUG;_CONSOLE"
 				MinimalRebuild="true"
 				BasicRuntimeChecks="3"
@@ -193,7 +193,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="2"
 				EnableIntrinsicFunctions="true"
-				AdditionalIncludeDirectories="..\;.\;..\..\;..\..\bios;..\..\cbus;..\..\common;..\..\embed;..\..\embed\menu;..\..\embed\menubase;..\..\fdd;..\..\font;..\..\generic;..\..\i286c;..\..\io;..\..\lio;..\..\mem;..\..\sound;..\..\vram;..\..\zlib"
+				AdditionalIncludeDirectories="..\;.\;..\..\;..\..\cbus;..\..\common;..\..\embed;..\..\embed\menu;..\..\embed\menubase;..\..\fdd;..\..\font;..\..\generic;..\..\i286c;..\..\io;..\..\mem;..\..\sound;..\..\vram;..\..\zlib"
 				PreprocessorDefinitions="WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS"
 				RuntimeLibrary="2"
 				EnableFunctionLevelLinking="true"
@@ -270,7 +270,7 @@
 				Name="VCCLCompilerTool"
 				Optimization="2"
 				EnableIntrinsicFunctions="true"
-				AdditionalIncludeDirectories="..\;.\;..\..\;..\..\bios;..\..\cbus;..\..\common;..\..\embed;..\..\embed\menu;..\..\embed\menubase;..\..\fdd;..\..\font;..\..\generic;..\..\i286c;..\..\io;..\..\lio;..\..\mem;..\..\sound;..\..\vram;..\..\zlib"
+				AdditionalIncludeDirectories="..\;.\;..\..\;..\..\cbus;..\..\common;..\..\embed;..\..\embed\menu;..\..\embed\menubase;..\..\fdd;..\..\font;..\..\generic;..\..\i286c;..\..\io;..\..\mem;..\..\sound;..\..\vram;..\..\zlib"
 				PreprocessorDefinitions="WIN32;NDEBUG;_CONSOLE;_CRT_SECURE_NO_WARNINGS"
 				RuntimeLibrary="2"
 				EnableFunctionLevelLinking="true"
diff --git a/statsave.c b/statsave.c
index c4fe7e24..c3a619fd 100644
--- a/statsave.c
+++ b/statsave.c
@@ -23,7 +23,7 @@
 #include "mpu98ii.h"
 #include "board14.h"
 #include "amd98.h"
-#include "bios.h"
+#include "bios/bios.h"
 #include "vram.h"
 #include "palettes.h"
 #include "maketext.h"
diff --git a/win9x/debuguty/viewcmn.cpp b/win9x/debuguty/viewcmn.cpp
index 6f3fcfe7..491b3460 100644
--- a/win9x/debuguty/viewcmn.cpp
+++ b/win9x/debuguty/viewcmn.cpp
@@ -14,7 +14,7 @@
 #include	"cpucore.h"
 #include	"pccore.h"
 #include	"iocore.h"
-#include	"bios.h"
+#include	"bios/bios.h"
 
 
 const char viewcmn_hex[16] = {
diff --git a/win9x/np2.cpp b/win9x/np2.cpp
index c2f2c921..e7ff1853 100644
--- a/win9x/np2.cpp
+++ b/win9x/np2.cpp
@@ -37,7 +37,6 @@
 #include "iocore.h"
 #include "pc9861k.h"
 #include "mpu98ii.h"
-#include "bios.h"
 #include "scrndraw.h"
 #include "sound.h"
 #include "beep.h"
diff --git a/win9x/np21base.props b/win9x/np21base.props
index c4f6ef95..b1dab705 100644
--- a/win9x/np21base.props
+++ b/win9x/np21base.props
@@ -9,7 +9,7 @@
   </PropertyGroup>
   <ItemDefinitionGroup>
     <ClCompile>
-      <AdditionalIncludeDirectories>..\win9x;..\win9x\dialog;..\win9x\mountdir;..\win9x\debuguty;..\;..\common;..\i386c;..\i386c\ia32;..\i386c\ia32\instructions;..\i386c\ia32\instructions\fpu;..\mem;..\io;..\cbus;..\bios;..\lio;..\vram;..\sound;..\fdd;..\font;..\generic;..\zlib;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
+      <AdditionalIncludeDirectories>..\win9x;..\win9x\dialog;..\win9x\mountdir;..\win9x\debuguty;..\;..\common;..\i386c;..\i386c\ia32;..\i386c\ia32\instructions;..\i386c\ia32\instructions\fpu;..\mem;..\io;..\cbus;..\vram;..\sound;..\fdd;..\font;..\generic;..\zlib;%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
       <DisableSpecificWarnings>4819;4996</DisableSpecificWarnings>
       <PreprocessorDefinitions>WIN32;_WINDOWS;SUPPORT_PC9821;%(PreprocessorDefinitions)</PreprocessorDefinitions>
     </ClCompile>
diff --git a/x11/Makefile.am b/x11/Makefile.am
index 7ada1bb3..8c0989b3 100644
--- a/x11/Makefile.am
+++ b/x11/Makefile.am
@@ -226,13 +226,11 @@ AM_CPPFLAGS=	-I$(real_topsrcdir) \
 		-I$(real_topsrcdir)/x11/gtk2 \
 		-I$(real_topsrcdir)/x11/debug \
 		-I$(real_topsrcdir)/common \
-		-I$(real_topsrcdir)/bios \
 		-I$(real_topsrcdir)/cbus \
 		-I$(real_topsrcdir)/fdd \
 		-I$(real_topsrcdir)/font \
 		-I$(real_topsrcdir)/generic \
 		-I$(real_topsrcdir)/io \
-		-I$(real_topsrcdir)/lio \
 		-I$(real_topsrcdir)/mem \
 		-I$(real_topsrcdir)/sound \
 		-I$(real_topsrcdir)/vram \