diff --git a/cpu.js b/cpu.js
index 9f083c4..38b7c90 100644
--- a/cpu.js
+++ b/cpu.js
@@ -84,7 +84,7 @@ const Instructions = {
   },
 
   store_addr: (addr) => {
-    CPU.currentInstruction.mnemonic = 'STO addr';
+    CPU.currentInstruction.mnemonic = `STO addr; @addr: ${num2hex(CPU.memory[addr])}`;
     CPU.memory[CPU.memory[addr]] = CPU.Acc;
     CPU.incrementIP(2);
   },
@@ -333,28 +333,27 @@ async function stepCPU(debugInfo, debug = false, prettyPrintDisplay = false) {
       CPU.running = false;
     }
   }
-  if (CPU.running) {
-    if (CPU.IP >= CPU.memory.length) {
-      console.error('HALTING - IP greater than memory size');
-      CPU.running = false;
+  if (CPU.IP >= CPU.memory.length) {
+    console.error('HALTING - IP greater than memory size');
+    CPU.running = false;
+    process.exit();
+  } else {
+    CPU.currentInstruction.opcode = CPU.memory[CPU.IP];
+    CPU.currentInstruction.operand = CPU.memory[CPU.IP+1];
+    let executeInstruction = opcodes2mnemonics[CPU.currentInstruction.opcode];
+    if (typeof executeInstruction === 'undefined') {
+      let info = debugInfo[CPU.previousIP];
+      console.error();
+      console.error(`Error: Invalid opcode`);
+      console.error(`  Executing $${num2hex(info.machine[0])} $${num2hex(info.machine[1])}`);
+      console.error(`  from line ${info.lineNumber}: ${info.source}`);
       process.exit();
-    } else {
-      CPU.currentInstruction.opcode = CPU.memory[CPU.IP];
-      CPU.currentInstruction.operand = CPU.memory[CPU.IP+1];
-      let executeInstruction = opcodes2mnemonics[CPU.currentInstruction.opcode];
-      if (typeof executeInstruction === 'undefined') {
-        let info = debugInfo[CPU.previousIP];
-        console.error();
-        console.error(`Error: Invalid opcode`);
-        console.error(`  Executing $${num2hex(info.machine[0])} $${num2hex(info.machine[1])}`);
-        console.error(`  from line ${info.lineNumber}: ${info.source}`);
-        process.exit();
-      }
-      executeInstruction(CPU.currentInstruction.operand);
-      CPU.cycleCounter += 1;
     }
+    executeInstruction(CPU.currentInstruction.operand);
+    CPU.cycleCounter += 1;
   }
   logCPUState(debugInfo, debug, prettyPrintDisplay);
+  if (!CPU.running) process.exit();
 }
 
 /**
@@ -374,7 +373,7 @@ exports.runProgram =
       // Animate the output by pausing between steps
       const loop = setInterval(async () => {
         stepCPU(debugInfo, debug, prettyPrint);
-        if (!CPU.running) clearInterval(loop);
+        if (!CPU.running) process.exit();
       }, clockSpeed);
     }
   };