diff --git a/02. Algorithms/09. Checksum Calc/ones_complement_checksum16bit.js b/02. Algorithms/09. Checksum Calc/ones_complement_checksum16bit.js
new file mode 100644
index 00000000..029cb7c0
--- /dev/null
+++ b/02. Algorithms/09. Checksum Calc/ones_complement_checksum16bit.js	
@@ -0,0 +1,36 @@
+
+const checksumCalc = (data)  => {
+
+    // adding all the bytes
+    const total = data.reduce((acc, num) => {
+        return acc + num;
+    });
+
+    // taking inverse of the total
+    const totalInverse = total ^ ~0;
+
+    // appending the inversed byte at the end.
+    data.push(totalInverse);
+
+    // tinkering with a byte to simulate the data change
+    // data[3] = 22;
+    return data;
+}
+
+const checksum = (data) => {
+
+    let total = 0;
+    for(let i = 0; i < data.length - 1; i++) {
+        total += data[i];
+    }
+
+    const inverseTotal = total ^ data[data.length - 1];
+
+    // inverseTotal should Have all bytes set to one. negeting it should give us 0. If it's 0 then the data is safe.
+    return ~inverseTotal === 0;
+}
+
+
+// data is an array of numbers
+const data = [12,34,54,66,90];
+console.log(checksum(checksumCalc(data)));