diff --git a/src/lib.rs b/src/lib.rs
index 2dd1ce8..ee2d47a 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,14 +1 @@
-struct Stack {
-    array: [i32],
-    ptr: u16
-}
-
-impl Stack {
-    pub fn push() {
-
-    }
-}
-
-fn test() {
-
-}
\ No newline at end of file
+mod model;
diff --git a/src/model.rs b/src/model.rs
new file mode 100644
index 0000000..e8b6dd9
--- /dev/null
+++ b/src/model.rs
@@ -0,0 +1,87 @@
+pub struct OperandStack {
+    vec: Vec<i32>,
+}
+
+impl OperandStack {
+    pub fn new() -> OperandStack {
+        OperandStack {
+            vec: vec![],
+        }
+    }
+
+    pub fn pop(&mut self) -> i32 {
+        self.vec.pop().unwrap()
+    }
+
+    pub fn push(&mut self, n: i32) {
+        self.vec.push(n);
+    }
+
+    pub fn swap(&mut self) {
+        let len = self.vec.len();
+        self.vec.swap(len- 1, len - 2);
+    }
+}
+
+pub struct LocalVariables {
+    vec: Vec<i32>
+}
+
+impl LocalVariables {
+    pub fn new(size: usize) -> LocalVariables {
+        LocalVariables {
+            vec: vec![0; size]
+        }
+    }
+
+    pub fn store(&mut self, address: u16, value: i32) {
+        self.vec.insert(address as usize, value);
+    }
+
+    pub fn store2(&mut self, address: u16, value1: i32, value2: i32) {
+        self.vec.insert(address as usize, value1);
+        self.vec.insert(address as usize + 1, value2);
+    }
+
+    pub fn load(&self, address: u16) -> i32 {
+        self.vec[address as usize]
+    }
+    pub fn load2(&self, address: u16) -> (i32, i32) {
+        (self.vec[address as usize], self.vec[address as usize + 1])
+    }
+
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::model::{LocalVariables, OperandStack};
+
+    #[test]
+    fn operand_stack() {
+        let mut stack = OperandStack::new();
+
+        stack.push(10);
+        stack.push(20);
+        stack.push(30);
+        stack.push(40);
+        stack.swap();
+
+        assert_eq!(stack.pop(), 30);
+        assert_eq!(stack.pop(), 40);
+        assert_eq!(stack.pop(), 20);
+        assert_eq!(stack.pop(), 10);
+    }
+
+    #[test]
+    fn local_vars() {
+        let mut vars = LocalVariables::new(10);
+
+        vars.store(1, 546);
+        vars.store(2, 100);
+        vars.store2(3, 100, 466);
+
+        assert_eq!(vars.load(1), 546);
+        assert_eq!(vars.load(3), 100);
+        assert_eq!(vars.load(4), 466);
+    }
+}
\ No newline at end of file