diff --git a/src/queue/queue-data-structure.js b/src/queue/queue-data-structure.js
index 98ac0fd0..e4ab9ce6 100644
--- a/src/queue/queue-data-structure.js
+++ b/src/queue/queue-data-structure.js
@@ -6,23 +6,42 @@ class Queue {
 
   canEnqueue() {
     // ... your code goes here
+    if (this.queueControl.length === this.MAX_SIZE) {
+      return false
+    }
+    return true
   }
 
   isEmpty() {
     // ... your code goes here
+    if (this.queueControl.length === 0) {
+      return true
+    }
+    return false
   }
 
   enqueue(item) {
     // ... your code goes here
+    if (this.queueControl.length === this.MAX_SIZE) {
+      throw new Error('QUEUE_OVERFLOW');
+    }
+    this.queueControl.push(item)
+    return this.queueControl
+
   }
 
   dequeue() {
     // ... your code goes here
+    if (this.queueControl.length > 0) {
+      return this.queueControl.shift()
+    }
+    throw new Error('QUEUE_UNDERFLOW')
   }
 
   display() {
     // ... your code goes here
-  }  
+    return this.queueControl
+  }
 }
 
 // This is required to enable the automated tests, please ignore it.
diff --git a/src/stack/stack-data-structure.js b/src/stack/stack-data-structure.js
index 1106f6f3..12faa4b2 100644
--- a/src/stack/stack-data-structure.js
+++ b/src/stack/stack-data-structure.js
@@ -6,23 +6,42 @@ class Stack {
 
   canPush() {
     // ... your code goes here
+    if (this.stackControl.length === this.MAX_SIZE) {
+      return false
+    }
+    return true
   }
 
   isEmpty() {
     // ... your code goes here
+    if (this.stackControl.length === 0) {
+      return true
+    }
+    return false
   }
 
   push(item) {
     // ... your code goes here
+    if (this.stackControl.length === this.MAX_SIZE) {
+      throw new Error('STACK_OVERFLOW')
+    } else {
+      this.stackControl.push(item)
+      return this.stackControl
+    }
   }
 
   pop() {
     // ... your code goes here
+    if (this.stackControl.length === 0) {
+      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.