diff --git a/index.html b/index.html
index 33a9f13..3b678f3 100644
--- a/index.html
+++ b/index.html
@@ -10,6 +10,7 @@
 <script src="chipsim.js"></script>
 <script src="memtable.js"></script>
 <script src="macros.js"></script>
+<script src="testprogram.js"></script>
 
 <script type="text/javascript">
 function handleOnload() {
diff --git a/macros.js b/macros.js
index 293f004..25de10a 100644
--- a/macros.js
+++ b/macros.js
@@ -21,27 +21,34 @@
 */
 
 var memory = Array();
-var code = [0xa9, 0x00, 0x20, 0x10, 0x00, 0x4c, 0x02, 0x00, 
-            0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-            0xe8, 0x88, 0xe6, 0x40, 0x38, 0x69, 0x02, 0x60];
 var cycle = 0;
 var trace = Array();
 var logstream = Array();
 var running = false;
 
 function loadProgram(){
+	// a moderate size of static testprogram might be loaded
+	if(testprogram.length!=0 && testprogramAddress != undefined)
+		for(var i=0;testprogram[i]!=undefined;i++){
+			var a=testprogramAddress+i;
+			mWrite(a, testprogram[i]);
+			if(a<0x200)
+				setCellValue(a, testprogram[i]);
+		}
+	// a small test program or patch might be passed in the URL
 	if(userCode.length!=0)
-		code=userCode;
+		for(var i=0;i<userCode.length;i++){
+			if(userCode[i] != undefined){
+				mWrite(i, userCode[i]);
+				if(i<0x200)
+					setCellValue(i, userCode[i]);
+			}
+		}
 	// default reset vector will be 0x0000 because undefined memory reads as zero
 	if(userResetLow!=undefined)
 		mWrite(0xfffc, userResetLow);
 	if(userResetHigh!=undefined)
 		mWrite(0xfffd, userResetHigh);
-	for(var i=0;i<code.length;i++){
-		mWrite(i, code[i]);
-		if(i<0x200)
-			setCellValue(i, code[i]);
-	}
 }
 
 function go(){
diff --git a/testprogram.js b/testprogram.js
new file mode 100644
index 0000000..dff8bfa
--- /dev/null
+++ b/testprogram.js
@@ -0,0 +1,15 @@
+// This file testprogram.js can be substituted by one of several tests
+// which may not be redistributable
+// for example
+//    cbmbasic  loaded at 0xa000 with entry point 0xe394
+//    test6502 (by Bird Computer) loaded at 0x8000 with entry point 0x8000
+//
+// (can use xxd -i to convert binary into C include syntax, as a starting point)
+//
+testprogramAddress=0x0000;
+
+testprogram = [
+	0xa9, 0x00, 0x20, 0x10, 0x00, 0x4c, 0x02, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+	0xe8, 0x88, 0xe6, 0x40, 0x38, 0x69, 0x02, 0x60
+];