sim65 common define for paravirt hooks base location

allows the loaded binary to take up as much space as possible
restored some documentation of the hooks but without reference to specific location

src/sim65/main.c

@@ -200,8 +200,8 @@ static unsigned char ReadProgramFile (void)
     /* Read the file body into memory */
     Addr = Load;
     while ((Val = fgetc(F)) != EOF) {
-        if (Addr == 0xFF00) {
-            Error ("'%s': To large to fit into $%04X-$FFF0", ProgramFile, Addr);
+        if (Addr >= PARAVIRT_BASE) {
+            Error ("'%s': To large to fit into $%04X-$%04X", ProgramFile, Addr, PARAVIRT_BASE);
         }
         MemWriteByte (Addr++, (unsigned char) Val);
     }

src/sim65/paravirt.c

@@ -318,13 +318,13 @@ void ParaVirtHooks (CPURegs* Regs)
 /* Potentially execute paravirtualization hooks */
 {
     /* Check for paravirtualization address range */
-    if (Regs->PC <  0xFFF4 ||
-        Regs->PC >= 0xFFF4 + sizeof (Hooks) / sizeof (Hooks[0])) {
+    if (Regs->PC <  PARAVIRT_BASE ||
+        Regs->PC >= PARAVIRT_BASE + sizeof (Hooks) / sizeof (Hooks[0])) {
         return;
     }
 
     /* Call paravirtualization hook */
-    Hooks[Regs->PC - 0xFFF4] (Regs);
+    Hooks[Regs->PC - PARAVIRT_BASE] (Regs);
 
     /* Simulate RTS */
     Regs->PC = Pop(Regs) + (Pop(Regs) << 8) + 1;

src/sim65/paravirt.h

@@ -38,6 +38,17 @@
 
 
 
+/*****************************************************************************/
+/*                                   Data                                    */
+/*****************************************************************************/
+
+
+
+#define PARAVIRT_BASE        0xFFF4
+/* Lowest address used by a paravirtualization hook */
+
+
+
 /*****************************************************************************/
 /*                                   Code                                    */
 /*****************************************************************************/