diff --git a/Cargo.toml b/Cargo.toml
index 09c55c4..b0dfb8d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -7,4 +7,8 @@ edition = "2021"
 name = "dmc"
 path = "src/bin/compiler/main.rs"
 
+[[bin]]
+name = "dm"
+path = "src/bin/dvm/main.rs"
+
 [dependencies]
diff --git a/src/bin/dvm/main.rs b/src/bin/dvm/main.rs
new file mode 100644
index 0000000..2e87359
--- /dev/null
+++ b/src/bin/dvm/main.rs
@@ -0,0 +1,14 @@
+use std::process::exit;
+use deimos::vm::DmVirtualMachine;
+use deimos::vm::op_codes::{add_mov_int, add_platform_call_to};
+
+fn main() {
+    let mut code: Vec<u8> = Vec::new();
+    add_mov_int(&mut code, 0, 42);
+    add_platform_call_to(&mut code, &String::from("std::core::print"), 1, &vec![0u8]);
+    let mut vm = DmVirtualMachine::new();
+    if let Err(_) = vm.run(&mut code) {
+        eprintln!("There was an exception.");
+        exit(1);
+    }
+}
\ No newline at end of file
diff --git a/src/vm/mod.rs b/src/vm/mod.rs
index 7398436..013f79f 100644
--- a/src/vm/mod.rs
+++ b/src/vm/mod.rs
@@ -1,35 +1,309 @@
-mod module;
-mod op_codes;
-mod platform;
-mod types;
+pub mod module;
+pub mod op_codes;
+pub mod platform;
+pub mod types;
 mod util;
 
 use crate::vm::module::DmFunction;
+use crate::vm::platform::init_platform_functions;
 use op_codes::*;
-use platform::PlatformCallFrame;
 use std::alloc::{alloc_zeroed, dealloc, Layout};
 use std::collections::HashMap;
+use std::ops::Index;
 use types::DmType;
 use util::{get_32_le, get_64_le};
 
-pub type PlatformFunction = fn(&mut PlatformCallFrame) -> Result<Option<(u64, DmType)>, String>;
+pub type PlatformFunction = fn(PlatformCallFrame) -> Result<Option<(u64, DmType)>, String>;
 
-pub struct DmVirtualMachine {
-    registers: Vec<u64>,
-    register_types: Vec<DmType>,
-    platform_functions: HashMap<String, PlatformFunction>,
+enum CallFrame<'a> {
+    PlatformCall(PlatformCallFrame<'a>),
+    DeimosCall(DeimosCallFrame<'a>)
 }
 
-impl DmVirtualMachine {
-    pub fn call(
-        &self,
-        dm_function: &DmFunction,
-        args: Vec<u64>,
-        arg_types: Vec<DmType>,
-    ) -> Result<(u64, DmType), String> {
-        run(&dm_function.byte_code, todo!(), todo!());
-        todo!()
+pub struct PlatformCallFrame<'a> {
+    pub name: String,
+    pub args: Vec<u64>,
+    pub arg_types: Vec<DmType>,
+    pub vm: &'a mut DmVirtualMachine<'a>
+}
+
+struct DeimosCallFrame<'a> {
+    return_address: usize,
+    dm_function: &'a DmFunction
+}
+
+struct RegisterSet {
+    size: usize,
+    registers: Vec<u64>,
+    register_types: Vec<DmType>,
+}
+
+type RegisterValue = (u64, DmType);
+
+impl RegisterSet {
+    fn new(size: usize) -> RegisterSet {
+        RegisterSet {
+            size,
+            registers: vec![0; size],
+            register_types: vec![DmType::Unit; size],
+        }
     }
+
+    fn get(&self, register_number: usize) -> RegisterValue {
+        (self.registers[register_number], self.register_types[register_number])
+    }
+
+    fn set_u32(&mut self, register_number: usize, value: u32, dm_type: DmType) {
+        self.registers[register_number] = value as u64;
+        self.register_types[register_number] = dm_type;
+    }
+
+    fn set_u64(&mut self, register_number: usize, value: u64, dm_type: DmType) {
+        self.registers[register_number] = value;
+        self.register_types[register_number] = dm_type;
+    }
+
+    fn clear(&mut self) {
+        self.registers = vec![0; self.size];
+        self.register_types = vec![DmType::Unit; self.size];
+    }
+
+    fn ensure_capacity(&mut self, size: usize) {
+        self.registers.resize(size, 0);
+        self.register_types.resize(size, DmType::Unit);
+    }
+
+    fn iter(&self) -> RegisterSetIterator {
+        RegisterSetIterator::new(&self.registers, &self.register_types)
+    }
+}
+
+struct RegisterSetIterator<'a> {
+    i: usize,
+    registers: &'a Vec<u64>,
+    register_types: &'a Vec<DmType>,
+}
+
+impl RegisterSetIterator<'_> {
+    fn new<'a>(registers: &'a Vec<u64>, register_types: &'a Vec<DmType>) -> RegisterSetIterator<'a> {
+        RegisterSetIterator {
+            i: 0usize,
+            registers,
+            register_types
+        }
+    }
+}
+
+impl<'a> Iterator for RegisterSetIterator<'a> {
+    type Item = RegisterValue;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.i < self.registers.len() {
+            let some = Some((self.registers[self.i], self.register_types[self.i]));
+            self.i += 1;
+            some
+        } else {
+            None
+        }
+    }
+}
+
+impl Clone for RegisterSet {
+    fn clone(&self) -> Self {
+        RegisterSet {
+            size: self.size,
+            registers: self.registers.clone(),
+            register_types: self.register_types.clone(),
+        }
+    }
+}
+
+pub struct DmVirtualMachine<'a> {
+    platform_functions: HashMap<String, PlatformFunction>,
+    ip: usize,
+    call_stack: Vec<CallFrame<'a>>,
+    register_set: RegisterSet,
+    register_state_stack: Vec<RegisterSet>,
+}
+
+impl DmVirtualMachine<'_> {
+    pub fn new<'a>() -> DmVirtualMachine<'a> {
+        DmVirtualMachine {
+            ip: 0,
+            register_set: RegisterSet::new(0),
+            platform_functions: init_platform_functions(),
+            call_stack: Vec::new(),
+            register_state_stack: Vec::new(),
+        }
+    }
+
+    pub fn call<const ArgLen: usize>(
+        &mut self,
+        dm_function: &DmFunction,
+        args: [u64; ArgLen],
+        arg_types: [DmType; ArgLen],
+    ) -> Result<(u64, DmType), String> {
+        // save current state
+        self.call_stack.push(CallFrame::DeimosCall(DeimosCallFrame {
+            return_address: self.ip,
+            dm_function
+        }));
+        self.register_state_stack.push(self.register_set.clone());
+
+        // zero registers and make sure there are enough for dm_function
+        self.register_set.clear();
+        self.register_set.ensure_capacity(dm_function.num_registers);
+
+        // push args
+        for i in 0..args.len() {
+            let arg = args[i];
+            let arg_type = arg_types[i];
+            self.register_set.set_u64(i, arg, arg_type);
+        }
+
+        // run the byte code
+        let call_result = self.run(&dm_function.byte_code);
+
+        // restore state
+        self.register_set = self.register_state_stack.pop().unwrap();
+        if let CallFrame::DeimosCall(deimos_call_frame) = self.call_stack.pop().unwrap() {
+            self.ip = deimos_call_frame.return_address;
+        }
+
+        // return result
+        if let Err(_) = call_result {
+            Err(String::from(format!("Failed to execute function {}", &dm_function.name)))
+        } else {
+            Ok(self.register_set.get(0))
+        }
+    }
+
+    pub fn run(&mut self, code: &Vec<u8>) -> Result<(), ()> {
+        let mut i = 0;
+        while i < code.len() {
+            match code[i] {
+                MOV_INT => {
+                    let target_register = code[i + 1] as usize;
+                    let operand = get_32_le!(code, i, 2, u32);
+                    self.register_set.set_u32(target_register, operand, DmType::Int);
+                    i += 6;
+                }
+                MOV_LONG => {
+                    let target_register = code[i + 1] as usize;
+                    let operand = get_64_le!(code, i, 2, u64);
+                    self.register_set.set_u64(target_register, operand, DmType::Long);
+                    i += 10;
+                }
+                MOV_DOUBLE => { /* todo */ }
+                MOV_REGISTER => {
+                    let target_register = code[i + 1] as usize;
+                    let source_register = code[i + 2] as usize;
+                    let (value, dm_type) = self.register_set.get(source_register);
+                    self.register_set.set_u64(target_register, value, dm_type);
+                    i += 3;
+                }
+                ALLOC => {
+                    let target_register = code[i + 1] as usize;
+                    let size = get_32_le!(code, i, 2, usize);
+                    let layout = Layout::from_size_align(size, 4).unwrap();
+                    let pointer = unsafe { alloc_zeroed(layout) };
+                    let dm_object = Box::new(DmObject {
+                        data: pointer,
+                        size,
+                        layout,
+                        object_type: todo!(),
+                    });
+                    let dm_object_pointer = Box::into_raw(dm_object) as u64;
+                    self.register_set.set_u64(target_register, dm_object_pointer as u64, DmType::Pointer);
+                    i += 6;
+                }
+                DEALLOC => {
+                    let target_register = code[i + 1] as usize;
+                    let (box_address, register_type) = self.register_set.get(target_register);
+                    if register_type != DmType::Pointer {
+                        panic!("Attempt to deallocate at the address stored in a register that is not a pointer.");
+                    }
+                    unsafe {
+                        let dm_object = Box::from_raw(box_address as *mut DmObject);
+                        dealloc(dm_object.data, dm_object.layout);
+                    }
+                    self.register_set.set_u64(target_register, 0, DmType::Unit);
+                    i += 2;
+                }
+                MOV_INT_TO => {
+                    let target_register = code[i + 1] as usize;
+                    let (box_address, register_type) = self.register_set.get(target_register);
+                    if register_type != DmType::Pointer {
+                        panic!("target_register {} is not a Pointer", target_register);
+                    }
+                    let offset = get_32_le!(code, i, 2, isize);
+                    let new_address = unsafe {
+                        let dm_object = Box::from_raw(box_address as *mut DmObject);
+                        let pointer = dm_object.data;
+                        pointer.offset(offset).write(code[i + 6]);
+                        pointer.offset(offset + 1).write(code[i + 7]);
+                        pointer.offset(offset + 2).write(code[i + 8]);
+                        pointer.offset(offset + 3).write(code[i + 9]);
+                        Box::into_raw(dm_object) as u64
+                    };
+                    self.register_set.set_u64(target_register, new_address, DmType::Pointer);
+                    i += 10;
+                }
+                PLATFORM_CALL => {
+                    i += 1;
+
+                    let symbol_name_length = get_32_le!(code, i, 1, usize);
+                    i += 4;
+
+                    let symbol_name_raw = code[i..(i + symbol_name_length)].to_vec();
+                    i += symbol_name_length;
+
+                    let symbol_name = String::from_utf8(symbol_name_raw).unwrap();
+
+                    let arg_registers_length = code[i] as usize;
+                    i += 1;
+
+                    let arg_registers = code[i..(i + arg_registers_length)].to_vec();
+                    i += arg_registers_length;
+
+                    let platform_function_result = self.platform_functions.get(&symbol_name);
+                    if platform_function_result.is_none() {
+                        panic!("Unknown function {}", symbol_name);
+                    }
+                    let platform_function = platform_function_result.unwrap();
+
+                    let mut args = Vec::new();
+                    let mut arg_types = Vec::new();
+                    for (value, dm_type) in self.register_set.iter() {
+                        args.push(value);
+                        arg_types.push(dm_type);
+                    }
+
+                    match platform_function(PlatformCallFrame {
+                        name: symbol_name,
+                        args,
+                        arg_types,
+                        vm: self
+                    }) {
+                        Ok(result_opt) => {
+                            match result_opt {
+                                Some((result, result_type)) => {
+                                    // todo: put in register
+                                },
+                                None => {
+                                    // TODO: put Unit in register
+                                }
+                            }
+                        },
+                        Err(e) => panic!("{}", e)
+                    }
+                }
+                _ => panic!("Invalid code instruction"),
+            }
+        }
+        Ok(())
+    }
+
 }
 
 pub struct DmObjectType {
@@ -56,83 +330,6 @@ pub struct DmObjectField {
     field_type: DmType,
 }
 
-pub fn run(code: &Vec<u8>, registers: &mut Vec<u64>, register_types: &mut Vec<DmType>) {
-    let mut i = 0;
-    while i < code.len() {
-        match code[i] {
-            MOV_INT => {
-                let target_register = code[i + 1] as usize;
-                let operand = get_32_le!(code, i, 2, u32);
-                registers[target_register] = operand as u64;
-                register_types[target_register] = DmType::Int;
-                i += 6;
-            }
-            MOV_LONG => {
-                let target_register = code[i + 1] as usize;
-                let operand = get_64_le!(code, i, 2, u64);
-                registers[target_register] = operand;
-                register_types[target_register] = DmType::Long;
-                i += 10;
-            }
-            MOV_DOUBLE => { /* todo */ }
-            MOV_REGISTER => {
-                let target_register = code[i + 1] as usize;
-                let source_register = code[i + 2] as usize;
-                registers[target_register] = registers[source_register];
-                register_types[target_register] = register_types[source_register].clone();
-                i += 3;
-            }
-            ALLOC => {
-                let target_register = code[i + 1] as usize;
-                let size = get_32_le!(code, i, 2, usize);
-                let layout = Layout::from_size_align(size, 4).unwrap();
-                let pointer = unsafe { alloc_zeroed(layout) };
-                let dm_object = Box::new(DmObject {
-                    data: pointer,
-                    size,
-                    layout,
-                    object_type: todo!(),
-                });
-                let dm_object_pointer = Box::into_raw(dm_object) as u64;
-                registers[target_register] = dm_object_pointer;
-                register_types[target_register] = DmType::Pointer;
-                i += 6;
-            }
-            DEALLOC => {
-                let target_register = code[i + 1] as usize;
-                let box_address = registers[target_register];
-                unsafe {
-                    let dm_object = Box::from_raw(box_address as *mut DmObject);
-                    dealloc(dm_object.data, dm_object.layout);
-                }
-                registers[target_register] = 0;
-                register_types[target_register] = DmType::Int;
-                i += 2;
-            }
-            MOV_INT_TO => {
-                let target_register = code[i + 1] as usize;
-                if register_types[target_register] != DmType::Pointer {
-                    panic!("target_register {} is not a Pointer", target_register);
-                }
-                let offset = get_32_le!(code, i, 2, isize);
-                let box_address = registers[target_register];
-                let new_address = unsafe {
-                    let dm_object = Box::from_raw(box_address as *mut DmObject);
-                    let pointer = dm_object.data;
-                    pointer.offset(offset).write(code[i + 6]);
-                    pointer.offset(offset + 1).write(code[i + 7]);
-                    pointer.offset(offset + 2).write(code[i + 8]);
-                    pointer.offset(offset + 3).write(code[i + 9]);
-                    Box::into_raw(dm_object) as u64
-                };
-                registers[target_register] = new_address;
-                i += 10;
-            }
-            _ => panic!("Invalid code instruction"),
-        }
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/vm/module.rs b/src/vm/module.rs
index 24d7804..cd5fbfa 100644
--- a/src/vm/module.rs
+++ b/src/vm/module.rs
@@ -24,6 +24,7 @@ pub enum DmConstant {
 pub struct DmFunction {
     pub name: String,
     pub byte_code: Vec<u8>,
+    pub num_registers: usize,
 }
 
 const CONST_SYMBOL: u8 = 0x01;
diff --git a/src/vm/op_codes.rs b/src/vm/op_codes.rs
index 01a2ecd..1ff5ecf 100644
--- a/src/vm/op_codes.rs
+++ b/src/vm/op_codes.rs
@@ -81,8 +81,12 @@ pub fn add_mov_int_to(code: &mut Vec<u8>, register: u8, offset: u32, operand: u3
     push_number!(code, operand);
 }
 
-pub fn add_platform_call_to(code: &mut Vec<u8>, symbol_name: &String) {
+pub fn add_platform_call_to(code: &mut Vec<u8>, symbol_name: &String, arg_registers_length: u8, arg_registers: &Vec<u8>) {
     code.push(PLATFORM_CALL);
     push_number!(code, symbol_name.len());
     push_string!(code, symbol_name);
+    push_number!(code, arg_registers_length);
+    for &b in arg_registers {
+        code.push(b);
+    }
 }
diff --git a/src/vm/platform/mod.rs b/src/vm/platform/mod.rs
index 4451f28..e451f06 100644
--- a/src/vm/platform/mod.rs
+++ b/src/vm/platform/mod.rs
@@ -1,15 +1,9 @@
 use crate::vm::platform::std_lib::core::dm_print;
-use crate::vm::{DmVirtualMachine, PlatformFunction};
+use crate::vm::PlatformFunction;
 use std::collections::HashMap;
 
 mod std_lib;
 
-pub struct PlatformCallFrame {
-    args: Vec<u64>,
-    arg_types: Vec<crate::vm::types::DmType>,
-    vm: DmVirtualMachine,
-}
-
 pub fn init_platform_functions() -> HashMap<String, PlatformFunction> {
     let mut fns: HashMap<String, PlatformFunction> = HashMap::new();
     fns.insert(String::from("std::core::print"), dm_print);
diff --git a/src/vm/platform/std_lib/core.rs b/src/vm/platform/std_lib/core.rs
index 61bb57b..3b7e052 100644
--- a/src/vm/platform/std_lib/core.rs
+++ b/src/vm/platform/std_lib/core.rs
@@ -1,5 +1,5 @@
-use crate::vm::platform::PlatformCallFrame;
 use crate::vm::types::DmType;
+use crate::vm::PlatformCallFrame;
 use crate::vm::DmObject;
 use DmType::*;
 
@@ -7,7 +7,7 @@ pub struct DmString {
     data: String,
 }
 
-pub fn dm_print(frame: &mut PlatformCallFrame) -> Result<Option<(u64, DmType)>, String> {
+pub fn dm_print(frame: PlatformCallFrame) -> Result<Option<(u64, DmType)>, String> {
     if frame.args.len() != 1 {
         return Err(String::from("std::core::print requires one argument."));
     }
@@ -28,10 +28,9 @@ pub fn dm_print(frame: &mut PlatformCallFrame) -> Result<Option<(u64, DmType)>,
                 .methods
                 .get(&String::from("to_string"))
             {
-                let call_result =
-                    frame
+                let call_result = frame
                         .vm
-                        .call(to_string_method, vec![frame.args[0]], vec![Pointer]);
+                        .call(&to_string_method, [frame.args[0]], [frame.arg_types[0]]);
                 if call_result.is_err() {
                     return Err(call_result.unwrap_err());
                 }
@@ -43,6 +42,12 @@ pub fn dm_print(frame: &mut PlatformCallFrame) -> Result<Option<(u64, DmType)>,
                 print!("{}@{:?}", dm_object.object_type.name, dm_object.data);
             }
         },
+        Unit => {
+            print!("Unit")
+        },
+        Exception => {
+            print!("Exception")
+        }
     }
     Ok(None)
 }
diff --git a/src/vm/types.rs b/src/vm/types.rs
index 09cad83..ecd8fc7 100644
--- a/src/vm/types.rs
+++ b/src/vm/types.rs
@@ -1,7 +1,9 @@
-#[derive(PartialEq, Eq, Clone, Debug)]
+#[derive(PartialEq, Eq, Clone, Debug, Copy)]
 pub enum DmType {
     Int,
     Long,
     Double,
     Pointer,
+    Unit,
+    Exception
 }