diff --git a/src/queue/queue-data-structure.js b/src/queue/queue-data-structure.js
index 98ac0fd0..9546f315 100644
--- a/src/queue/queue-data-structure.js
+++ b/src/queue/queue-data-structure.js
@@ -5,23 +5,36 @@ 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 false
+    }
+    return true
   }
 
   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..d33c7e17 100644
--- a/src/stack/stack-data-structure.js
+++ b/src/stack/stack-data-structure.js
@@ -5,23 +5,38 @@ 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 false
+    }
+    return true
   }
 
   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
   }  
 }