diff --git a/parts/platforms/README.md b/parts/platforms/README.md
new file mode 100644
index 0000000..08d9751
--- /dev/null
+++ b/parts/platforms/README.md
@@ -0,0 +1,5 @@
+# platforms
+
+This is a collection of include files that set platform-specific constants
+that different parts use. When assembling your own OS, pick the platform include
+that is closest to yours and adapt it to your machine.
diff --git a/parts/platforms/rc2014.inc b/parts/platforms/rc2014.inc
new file mode 100644
index 0000000..7fd92f0
--- /dev/null
+++ b/parts/platforms/rc2014.inc
@@ -0,0 +1,5 @@
+; classic RC2014 setup (8K ROM + 32K RAM) and a stock Serial I/O module
+
+RAMEND		.equ	0xa000
+ACIA_CTL	.equ	0x80	; Control and status. RS off.
+ACIA_IO		.equ	0x81	; Transmit. RS on.
diff --git a/parts/shell/shell.asm b/parts/shell/shell.asm
index 97eb0a7..f61ee21 100644
--- a/parts/shell/shell.asm
+++ b/parts/shell/shell.asm
@@ -5,13 +5,7 @@
 ; *** STATUS ***
 ; Incomplete. This just outputs the welcome prompt then halts
 
-; *** PLATFORM ***
-; this is specific to a classic RC2014 setup (8K ROM + 32K RAM). This will be
-; reorganized into something better.
-
-RAMEND		.equ	0xa000
-ACIA_CTL	.equ	0x80	; Control and status. RS off.
-ACIA_IO		.equ	0x81	; Transmit. RS on.
+#include "platform.inc"
 
 ; *** CONSTS ***
 CR	.equ	0x0d
diff --git a/recipes/rc2014.md b/recipes/rc2014.md
index e1edf1c..eefb580 100644
--- a/recipes/rc2014.md
+++ b/recipes/rc2014.md
@@ -31,7 +31,8 @@ device I use in this recipe.
 
 ### Gathering parts
 
-* `shell.asm` from `parts`
+* `parts/platforms/rc2014.inc` as `platform.inc`
+* `parts/shell/shell.asm` as `shell.asm`
 * [scas][scas]
 * [romwrite][romwrite] and its specified dependencies
 * [GNU screen][screen]