diff --git a/src/queue/queue-data-structure.js b/src/queue/queue-data-structure.js
index 98ac0fd0..d09018ad 100644
--- a/src/queue/queue-data-structure.js
+++ b/src/queue/queue-data-structure.js
@@ -5,23 +5,30 @@ class Queue {
   }
 
   canEnqueue() {
-    // ... your code goes here
+    return this.queueControl.length < this.MAX_SIZE
   }
 
   isEmpty() {
-    // ... your code goes here
+    return this.queueControl.length === 0;
   }
 
   enqueue(item) {
-    // ... your code goes here
+    if (!this.canEnqueue()) {
+      throw new Error("QUEUE_OVERFLOW");
+    }
+    this.queueControl.push(item);
+    return this.queueControl;
   }
 
   dequeue() {
-    // ... your code goes here
+    if (this.isEmpty()) {
+      throw new Error("QUEUE_UNDERFLOW");
+    }
+    return this.queueControl.shift();
   }
 
   display() {
-    // ... your code goes here
+    return this.queueControl;
   }  
 }
 
diff --git a/src/stack/stack-data-structure.js b/src/stack/stack-data-structure.js
index 1106f6f3..c5c2095d 100644
--- a/src/stack/stack-data-structure.js
+++ b/src/stack/stack-data-structure.js
@@ -5,25 +5,32 @@ class Stack {
   }
 
   canPush() {
-    // ... your code goes here
+    return this.stackControl.length < this.MAX_SIZE;
   }
 
   isEmpty() {
-    // ... your code goes here
+    return this.stackControl.length === 0;
   }
 
   push(item) {
-    // ... your code goes here
+    if (!this.canPush()) {
+      throw new Error("STACK_OVERFLOW");
+    }
+    this.stackControl.push(item);
+    return this.stackControl;
   }
 
   pop() {
-    // ... your code goes here
+    if (this.isEmpty()) {
+      throw new Error("STACK_UNDERFLOW");
+    }
+    return this.stackControl.pop();
   }
 
   display() {
-    // ... your code goes here
-  }  
+    return this.stackControl;
+  }
 }
 
 // This is required to enable the automated tests, please ignore it.
-if (typeof module !== 'undefined') module.exports = Stack;
+if (typeof module !== "undefined") module.exports = Stack;