A devices/system.c

@@ -0,0 +1,14 @@ 
+#include <stdio.h>
+#include "../xyw.h"
+
+#define SYSTEM_RANDOM 0x05
+
+xyw_byte system_input(xyw_byte *data, xyw_byte addr, xyw_byte *error)
+{
+    if (addr == SYSTEM_RANDOM)
+    {
+        // TODO
+    }
+    (void)error;
+    return data[addr];
+}

A devices/system.h

@@ -0,0 +1,4 @@ 
+#include "../xyw.h"
+
+void system_output(xyw_byte *data, xyw_byte addr, xyw_byte *error);
+xyw_byte system_input(xyw_byte *data, xyw_byte addr, xyw_byte *error);

M xywrun.c → xywrun.c

@@ -20,7 +20,8 @@ #define SYSTEM_ERROR 0xff01
 #define SYSTEM_S 0xff02
 #define SYSTEM_U 0xff03
 #define SYSTEM_PAGE 0xff04
-#define SYSTEM_ON_ERROR 0xff05
+#define SYSTEM_RANDOM 0xff05
+#define SYSTEM_ON_ERROR 0xff06
 
 #ifdef _WIN32
 #include <conio.h>