diff --git a/Cargo.lock b/Cargo.lock
index e2d9d37..6722a0f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -221,10 +221,18 @@ version = "0.1.0"
 dependencies = [
  "clap",
  "codespan-reporting 0.13.1",
+ "dm-std-lib",
  "dmc-lib",
  "dvm-lib",
 ]
 
+[[package]]
+name = "dm-std-lib"
+version = "0.1.0"
+dependencies = [
+ "dvm-lib",
+]
+
 [[package]]
 name = "dmc-lib"
 version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
index 08f07ab..4a95eea 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,7 +5,7 @@ edition = "2021"
 
 #[[bin]]
 #name = "dm"
-#path = "src/bin/dvm/main.rs"
+#path = "src/bin/dvm/lib"
 
 [[bin]]
 name = "dmc"
@@ -25,4 +25,4 @@ cst-test-generator = { path = "cst-test-generator" }
 
 [workspace]
 resolver = "3"
-members = ["ast-generator", "cst-test-generator", "dm", "dmc-lib", "dvm-lib"]
+members = ["ast-generator", "cst-test-generator", "dm", "dm-std-lib", "dmc-lib", "dvm-lib"]
diff --git a/dm-std-lib/Cargo.toml b/dm-std-lib/Cargo.toml
new file mode 100644
index 0000000..c3e8d65
--- /dev/null
+++ b/dm-std-lib/Cargo.toml
@@ -0,0 +1,7 @@
+[package]
+name = "dm-std-lib"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+dvm-lib = { path = "../dvm-lib" }
\ No newline at end of file
diff --git a/dm-std-lib/src/lib.rs b/dm-std-lib/src/lib.rs
new file mode 100644
index 0000000..f7e2fc2
--- /dev/null
+++ b/dm-std-lib/src/lib.rs
@@ -0,0 +1,61 @@
+use dvm_lib::vm::value::Value;
+use dvm_lib::vm::{DvmContext, DvmState};
+use std::error::Error;
+use std::fmt::{Debug, Display, Formatter};
+use std::rc::Rc;
+
+pub fn add_all_std_core(context: &mut DvmContext) {
+    let platform_functions = context.platform_functions_mut();
+    platform_functions.insert(Rc::from("println"), std_core_println);
+}
+
+struct StdCoreError {
+    message: String,
+}
+
+impl StdCoreError {
+    pub fn new(message: &str) -> StdCoreError {
+        Self {
+            message: message.into(),
+        }
+    }
+}
+
+impl Debug for StdCoreError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        todo!()
+    }
+}
+
+impl Display for StdCoreError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.message)
+    }
+}
+
+impl Error for StdCoreError {}
+
+pub fn std_core_println(
+    context: &DvmContext,
+    state: &DvmState,
+    args: &[Value],
+) -> Result<Value, Box<dyn Error>> {
+    let maybe_to_print = args.get(0);
+    match maybe_to_print {
+        None => Err(Box::new(StdCoreError::new("Missing to_print arg"))),
+        Some(to_print) => {
+            match to_print {
+                Value::Int(i) => {
+                    println!("{}", i);
+                }
+                Value::String(s) => {
+                    println!("{}", s);
+                }
+                Value::Null => {
+                    println!("null");
+                }
+            }
+            Ok(Value::Null)
+        }
+    }
+}
diff --git a/dm/Cargo.toml b/dm/Cargo.toml
index e70abb9..8c48197 100644
--- a/dm/Cargo.toml
+++ b/dm/Cargo.toml
@@ -6,5 +6,6 @@ edition = "2024"
 [dependencies]
 dmc-lib = { path = "../dmc-lib" }
 dvm-lib = { path = "../dvm-lib" }
+dm-std-lib = { path = "../dm-std-lib" }
 clap = { version = "4.5.60", features = ["derive"] }
 codespan-reporting = "0.13.1"
\ No newline at end of file
diff --git a/dm/src/main.rs b/dm/src/main.rs
index 6bb3716..4907871 100644
--- a/dm/src/main.rs
+++ b/dm/src/main.rs
@@ -3,6 +3,7 @@ use codespan_reporting::diagnostic::Label;
 use codespan_reporting::files::SimpleFiles;
 use codespan_reporting::term;
 use codespan_reporting::term::termcolor::{ColorChoice, StandardStream};
+use dm_std_lib::add_all_std_core;
 use dmc_lib::constants_table::ConstantsTable;
 use dmc_lib::diagnostic::Diagnostic;
 use dmc_lib::parser::parse_compilation_unit;
@@ -59,6 +60,9 @@ fn main() {
 
     let mut dvm_context = DvmContext::new();
 
+    // add std::core fns
+    add_all_std_core(&mut dvm_context);
+
     for asm_function in &asm_functions {
         let function = asm_function.dvm();
         dvm_context.add_function(function);
diff --git a/dmc-lib/src/asm/asm_instruction.rs b/dmc-lib/src/asm/asm_instruction.rs
index a3706a3..a8d7da4 100644
--- a/dmc-lib/src/asm/asm_instruction.rs
+++ b/dmc-lib/src/asm/asm_instruction.rs
@@ -103,15 +103,19 @@ impl Pop {
 #[derive(Debug)]
 pub struct InvokePlatformStatic {
     name: String,
+    arg_count: usize,
 }
 
 impl InvokePlatformStatic {
-    pub fn new(name: &str) -> Self {
-        Self { name: name.into() }
+    pub fn new(name: &str, arg_count: usize) -> Self {
+        Self {
+            name: name.into(),
+            arg_count,
+        }
     }
 
     pub fn dvm(&self) -> Instruction {
-        Instruction::InvokePlatformStatic(Rc::from(self.name.clone()))
+        Instruction::InvokePlatformStatic(Rc::from(self.name.clone()), self.arg_count)
     }
 }
 
diff --git a/dmc-lib/src/ast/call.rs b/dmc-lib/src/ast/call.rs
index aeb95d5..b578509 100644
--- a/dmc-lib/src/ast/call.rs
+++ b/dmc-lib/src/ast/call.rs
@@ -62,14 +62,51 @@ impl Call {
         }
 
         // check that callee is callable
-        match self.callee.type_info() {
-            TypeInfo::Function(_) => {}
+        let function_symbol = match self.callee.type_info() {
+            TypeInfo::Function(function_symbol) => function_symbol,
             _ => {
                 diagnostics.push(Diagnostic::new(
                     "Receiver is not callable",
                     self.callee.source_range().start(),
                     self.callee.source_range().end(),
                 ));
+                return diagnostics;
+            }
+        };
+
+        // check arguments length
+        let function_symbol_ref = function_symbol.borrow();
+        let parameters = function_symbol_ref.parameters();
+        if parameters.len() != self.arguments.len() {
+            diagnostics.push(Diagnostic::new(
+                &format!(
+                    "Wrong number of arguments; expected {} but found {}",
+                    parameters.len(),
+                    self.arguments.len()
+                ),
+                self.source_range.start(),
+                self.source_range.end(),
+            ));
+        }
+
+        if !diagnostics.is_empty() {
+            return diagnostics;
+        }
+
+        // check argument types
+        for i in 0..parameters.len() {
+            let parameter = &parameters[i];
+            let argument = &self.arguments[i];
+            if parameter.borrow().type_info() != &argument.type_info() {
+                diagnostics.push(Diagnostic::new(
+                    &format!(
+                        "Mismatched types; expected {} but found {}",
+                        parameter.borrow().type_info(),
+                        argument.type_info()
+                    ),
+                    argument.source_range().start(),
+                    argument.source_range().end(),
+                ))
             }
         }
 
@@ -78,7 +115,7 @@ impl Call {
 
     pub fn type_info(&self) -> TypeInfo {
         match self.callee.type_info() {
-            TypeInfo::Function(function_symbol) => function_symbol.return_type(),
+            TypeInfo::Function(function_symbol) => function_symbol.borrow().return_type(),
             _ => panic!(),
         }
     }
@@ -155,9 +192,11 @@ impl Call {
             _ => panic!("Calling things other than identifiers not yet supported."),
         };
 
+        let function_symbol = function_symbol.borrow();
         if function_symbol.is_platform() {
+            let arg_count = function_symbol.parameters().len();
             context.instruction(AsmInstruction::InvokePlatformStatic(
-                InvokePlatformStatic::new(function_symbol.name()),
+                InvokePlatformStatic::new(function_symbol.name(), arg_count),
             ));
         } else {
             todo!("non-platform invoke")
diff --git a/dmc-lib/src/ast/extern_function.rs b/dmc-lib/src/ast/extern_function.rs
index 04db97c..f038863 100644
--- a/dmc-lib/src/ast/extern_function.rs
+++ b/dmc-lib/src/ast/extern_function.rs
@@ -1,20 +1,29 @@
 use crate::ast::assemble_context::AssembleContext;
+use crate::ast::parameter::Parameter;
 use crate::constants_table::ConstantsTable;
 use crate::diagnostic::Diagnostic;
 use crate::source_range::SourceRange;
 use crate::symbol::FunctionSymbol;
 use crate::symbol_table::{SymbolInsertError, SymbolTable};
+use std::cell::RefCell;
+use std::rc::Rc;
 
 pub struct ExternFunction {
     declared_name: String,
     declared_name_source_range: SourceRange,
+    parameters: Vec<Parameter>,
 }
 
 impl ExternFunction {
-    pub fn new(name: &str, declared_name_source_range: SourceRange) -> ExternFunction {
+    pub fn new(
+        name: &str,
+        declared_name_source_range: SourceRange,
+        parameters: Vec<Parameter>,
+    ) -> ExternFunction {
         ExternFunction {
             declared_name: name.into(),
             declared_name_source_range,
+            parameters,
         }
     }
 
@@ -23,26 +32,52 @@ impl ExternFunction {
     }
 
     pub fn gather_declared_names(&mut self, symbol_table: &mut SymbolTable) -> Vec<Diagnostic> {
-        let insert_result = symbol_table.insert_function_symbol(FunctionSymbol::new(
-            &self.declared_name,
-            &vec![],
-            true,
-        ));
+        let mut diagnostics = vec![];
+
+        let insert_result =
+            symbol_table.insert_function_symbol(FunctionSymbol::new(&self.declared_name, true));
+
+        let mut maybe_function_symbol: Option<Rc<RefCell<FunctionSymbol>>> = None;
         match insert_result {
-            Ok(_) => vec![],
+            Ok(function_symbol) => {
+                maybe_function_symbol = Some(function_symbol);
+            }
             Err(symbol_insert_error) => match symbol_insert_error {
                 SymbolInsertError::AlreadyDeclared(already_declared) => {
-                    vec![Diagnostic::new(
+                    diagnostics.push(Diagnostic::new(
                         &format!(
                             "Function {} already declared in current scope.",
                             already_declared.name()
                         ),
                         self.declared_name_source_range.start(),
                         self.declared_name_source_range.end(),
-                    )]
+                    ));
                 }
             },
         }
+
+        symbol_table.push_scope(&format!("extern_function_scope({})", &self.declared_name));
+
+        let mut parameter_symbols = vec![];
+        for parameter in &mut self.parameters {
+            let parameter_result = parameter.gather_declared_names(symbol_table);
+            match parameter_result {
+                Ok(parameter_symbol) => {
+                    parameter_symbols.push(parameter_symbol);
+                }
+                Err(mut parameter_diagnostics) => {
+                    diagnostics.append(&mut parameter_diagnostics);
+                }
+            }
+        }
+        maybe_function_symbol
+            .unwrap()
+            .borrow_mut()
+            .set_parameters(parameter_symbols);
+
+        symbol_table.pop_scope();
+
+        diagnostics
     }
 
     pub fn check_name_usages(&mut self, symbol_table: &SymbolTable) -> Vec<Diagnostic> {
diff --git a/dmc-lib/src/ast/function.rs b/dmc-lib/src/ast/function.rs
index 61f1a7a..8da140b 100644
--- a/dmc-lib/src/ast/function.rs
+++ b/dmc-lib/src/ast/function.rs
@@ -40,11 +40,8 @@ impl Function {
     pub fn gather_declared_names(&mut self, symbol_table: &mut SymbolTable) -> Vec<Diagnostic> {
         let mut diagnostics = vec![];
         // insert function symbol
-        let insert_result = symbol_table.insert_function_symbol(FunctionSymbol::new(
-            self.declared_name(),
-            &vec![], // todo
-            false,
-        ));
+        let insert_result =
+            symbol_table.insert_function_symbol(FunctionSymbol::new(self.declared_name(), false));
         if let Err(symbol_insert_error) = insert_result {
             match symbol_insert_error {
                 SymbolInsertError::AlreadyDeclared(already_declared) => {
@@ -59,6 +56,9 @@ impl Function {
                 }
             }
         }
+
+        // todo: parameters
+
         symbol_table.push_scope(&format!("function_scope({})", self.declared_name()));
         for statement in &mut self.statements {
             diagnostics.append(&mut statement.gather_declared_names(symbol_table));
diff --git a/dmc-lib/src/ast/mod.rs b/dmc-lib/src/ast/mod.rs
index 4bde6d3..f422696 100644
--- a/dmc-lib/src/ast/mod.rs
+++ b/dmc-lib/src/ast/mod.rs
@@ -10,5 +10,6 @@ pub mod identifier;
 pub mod integer_literal;
 pub mod let_statement;
 pub mod module_level_declaration;
+pub mod parameter;
 pub mod statement;
 pub mod string_literal;
diff --git a/dmc-lib/src/ast/parameter.rs b/dmc-lib/src/ast/parameter.rs
new file mode 100644
index 0000000..e2e45ae
--- /dev/null
+++ b/dmc-lib/src/ast/parameter.rs
@@ -0,0 +1,41 @@
+use crate::diagnostic::Diagnostic;
+use crate::source_range::SourceRange;
+use crate::symbol::ParameterSymbol;
+use crate::symbol_table::{SymbolInsertError, SymbolTable};
+use crate::type_info::TypeInfo;
+use std::cell::RefCell;
+use std::rc::Rc;
+
+pub struct Parameter {
+    declared_name: String,
+    declared_name_source_range: SourceRange,
+}
+
+impl Parameter {
+    pub fn new(declared_name: &str, declared_name_source_range: SourceRange) -> Self {
+        Self {
+            declared_name: declared_name.into(),
+            declared_name_source_range,
+        }
+    }
+
+    pub fn gather_declared_names(
+        &mut self,
+        symbol_table: &mut SymbolTable,
+    ) -> Result<Rc<RefCell<ParameterSymbol>>, Vec<Diagnostic>> {
+        let insert_result = symbol_table.insert_parameter_symbol(ParameterSymbol::new(
+            &self.declared_name,
+            TypeInfo::String, // todo
+        ));
+        match insert_result {
+            Ok(parameter_symbol) => Ok(parameter_symbol),
+            Err(symbol_insert_error) => match symbol_insert_error {
+                SymbolInsertError::AlreadyDeclared(already_declared) => Err(vec![Diagnostic::new(
+                    &format!("Parameter {} already declared.", already_declared.name()),
+                    self.declared_name_source_range.start(),
+                    self.declared_name_source_range.end(),
+                )]),
+            },
+        }
+    }
+}
diff --git a/dmc-lib/src/ir/ir_call.rs b/dmc-lib/src/ir/ir_call.rs
index 67d449e..27bf7ef 100644
--- a/dmc-lib/src/ir/ir_call.rs
+++ b/dmc-lib/src/ir/ir_call.rs
@@ -46,7 +46,7 @@ impl IrCall {
             }
         }
         instructions.push(AsmInstruction::InvokePlatformStatic(
-            InvokePlatformStatic::new(&self.name),
+            InvokePlatformStatic::new(&self.name, todo!()),
         ));
         instructions
     }
diff --git a/dmc-lib/src/lexer.rs b/dmc-lib/src/lexer.rs
index c7d4606..4a74f94 100644
--- a/dmc-lib/src/lexer.rs
+++ b/dmc-lib/src/lexer.rs
@@ -44,6 +44,8 @@ impl<'a> Lexer<'a> {
             )
         } else if chunk.starts_with("=") {
             Token::new(self.position, self.position + 1, TokenKind::Equals)
+        } else if chunk.starts_with(",") {
+            Token::new(self.position, self.position + 1, TokenKind::Comma)
         } else {
             // more than one char token
             if chunk.starts_with(|c: char| c.is_ascii_digit()) {
diff --git a/dmc-lib/src/parser.rs b/dmc-lib/src/parser.rs
index 5099c85..4800860 100644
--- a/dmc-lib/src/parser.rs
+++ b/dmc-lib/src/parser.rs
@@ -8,6 +8,7 @@ use crate::ast::identifier::Identifier;
 use crate::ast::integer_literal::IntegerLiteral;
 use crate::ast::let_statement::LetStatement;
 use crate::ast::module_level_declaration::ModuleLevelDeclaration;
+use crate::ast::parameter::Parameter;
 use crate::ast::statement::Statement;
 use crate::ast::string_literal::StringLiteral;
 use crate::diagnostic::Diagnostic;
@@ -138,6 +139,13 @@ impl<'a> Parser<'a> {
         }
     }
 
+    fn peek_lookahead(&self, token_kind: TokenKind) -> bool {
+        match &self.lookahead {
+            None => panic!("Unexpected end of input."),
+            Some(token) => token.kind() == token_kind,
+        }
+    }
+
     fn sample_input(&self, start: usize, end: usize) -> &'a str {
         &self.input[start..end]
     }
@@ -251,10 +259,62 @@ impl<'a> Parser<'a> {
         self.expect_advance(TokenKind::Fn)?;
         let identifier_token = self.expect_advance(TokenKind::Identifier)?;
         self.expect_advance(TokenKind::LeftParentheses)?;
-        // params
-        self.expect_advance(TokenKind::RightParentheses)?;
-        // return type
-        Ok(ExternFunction::new(
+
+        let mut diagnostics = vec![];
+
+        let mut maybe_parameters: Option<Vec<Parameter>> = None;
+        let params_result = self.parameter_list();
+        match params_result {
+            Ok(parameters) => {
+                maybe_parameters = Some(parameters);
+            }
+            Err(mut parameter_list_diagnostics) => {
+                diagnostics.append(&mut parameter_list_diagnostics);
+            }
+        }
+
+        let right_parentheses_result = self.expect_advance(TokenKind::RightParentheses);
+        match right_parentheses_result {
+            Err(mut right_parentheses_diagnostics) => {
+                diagnostics.append(&mut right_parentheses_diagnostics);
+            }
+            Ok(_) => {}
+        }
+
+        if diagnostics.is_empty() {
+            Ok(ExternFunction::new(
+                self.token_text(&identifier_token),
+                SourceRange::new(identifier_token.start(), identifier_token.end()),
+                maybe_parameters.unwrap(),
+            ))
+        } else {
+            Err(diagnostics)
+        }
+    }
+
+    fn parameter_list(&mut self) -> Result<Vec<Parameter>, Vec<Diagnostic>> {
+        let mut parameters = vec![];
+        let mut diagnostics = vec![];
+        while self.current.is_some() && self.peek_current(TokenKind::Identifier) {
+            let parameter_result = self.parameter();
+            match parameter_result {
+                Ok(parameter) => {
+                    parameters.push(parameter);
+                }
+                Err(mut parameter_diagnostics) => {
+                    diagnostics.append(&mut parameter_diagnostics);
+                }
+            }
+            if self.lookahead.is_some() && self.peek_lookahead(TokenKind::Comma) {
+                self.advance();
+            }
+        }
+        Ok(parameters)
+    }
+
+    fn parameter(&mut self) -> Result<Parameter, Vec<Diagnostic>> {
+        let identifier_token = self.expect_advance(TokenKind::Identifier)?;
+        Ok(Parameter::new(
             self.token_text(&identifier_token),
             SourceRange::new(identifier_token.start(), identifier_token.end()),
         ))
@@ -381,9 +441,56 @@ impl<'a> Parser<'a> {
 mod smoke_tests {
     use super::*;
 
+    fn smoke_test(input: &str) {
+        let parse_result = parse_compilation_unit(input);
+        match parse_result {
+            Ok(_) => {}
+            Err(diagnostics) => {
+                eprintln!("{:#?}", diagnostics);
+                panic!("There were diagnostics during parsing");
+            }
+        }
+    }
+
     #[test]
     fn forty_two() {
-        parse_compilation_unit("fn main() 42 end");
+        smoke_test("fn main() 42 end");
+    }
+
+    #[test]
+    fn chained_calls() {
+        smoke_test("fn main() getCl()() end");
+    }
+
+    #[test]
+    fn extern_fn_with_param() {
+        smoke_test("extern fn println(message)")
+    }
+}
+
+#[cfg(test)]
+mod concrete_tests {
+    use super::*;
+
+    #[test]
+    fn parses_extern_fn() {
+        let parse_result = parse_compilation_unit("extern fn println()");
+        let compilation_unit = match parse_result {
+            Ok(compilation_unit) => compilation_unit,
+            Err(diagnostics) => {
+                for diagnostic in diagnostics {
+                    eprintln!("{:?}", diagnostic);
+                }
+                panic!();
+            }
+        };
+        let declarations = compilation_unit.declarations();
+        assert_eq!(declarations.len(), 1);
+        let extern_function = match &declarations[0] {
+            ModuleLevelDeclaration::ExternFunction(extern_function) => extern_function,
+            _ => panic!(),
+        };
+        assert_eq!(extern_function.declared_name(), "println");
     }
 
     #[test]
@@ -432,37 +539,6 @@ mod smoke_tests {
             panic!("Expected expression");
         }
     }
-
-    #[test]
-    fn chained_calls() {
-        parse_compilation_unit("fn main() getCl()() end");
-    }
-}
-
-#[cfg(test)]
-mod concrete_tests {
-    use super::*;
-
-    #[test]
-    fn parses_extern_fn() {
-        let parse_result = parse_compilation_unit("extern fn println()");
-        let compilation_unit = match parse_result {
-            Ok(compilation_unit) => compilation_unit,
-            Err(diagnostics) => {
-                for diagnostic in diagnostics {
-                    eprintln!("{:?}", diagnostic);
-                }
-                panic!();
-            }
-        };
-        let declarations = compilation_unit.declarations();
-        assert_eq!(declarations.len(), 1);
-        let extern_function = match &declarations[0] {
-            ModuleLevelDeclaration::ExternFunction(extern_function) => extern_function,
-            _ => panic!(),
-        };
-        assert_eq!(extern_function.declared_name(), "println");
-    }
 }
 
 #[cfg(test)]
diff --git a/dmc-lib/src/scope.rs b/dmc-lib/src/scope.rs
index 8e2d68b..5804a53 100644
--- a/dmc-lib/src/scope.rs
+++ b/dmc-lib/src/scope.rs
@@ -6,7 +6,7 @@ use std::rc::Rc;
 pub struct Scope {
     debug_name: String,
     parent_id: Option<usize>,
-    function_symbols: HashMap<Rc<str>, Rc<FunctionSymbol>>,
+    function_symbols: HashMap<Rc<str>, Rc<RefCell<FunctionSymbol>>>,
     parameter_symbols: HashMap<Rc<str>, Rc<RefCell<ParameterSymbol>>>,
     variable_symbols: HashMap<Rc<str>, Rc<RefCell<VariableSymbol>>>,
 }
@@ -22,11 +22,11 @@ impl Scope {
         }
     }
 
-    pub fn function_symbols(&self) -> &HashMap<Rc<str>, Rc<FunctionSymbol>> {
+    pub fn function_symbols(&self) -> &HashMap<Rc<str>, Rc<RefCell<FunctionSymbol>>> {
         &self.function_symbols
     }
 
-    pub fn function_symbols_mut(&mut self) -> &mut HashMap<Rc<str>, Rc<FunctionSymbol>> {
+    pub fn function_symbols_mut(&mut self) -> &mut HashMap<Rc<str>, Rc<RefCell<FunctionSymbol>>> {
         &mut self.function_symbols
     }
 
diff --git a/dmc-lib/src/symbol.rs b/dmc-lib/src/symbol.rs
index b3d2fba..f5c53eb 100644
--- a/dmc-lib/src/symbol.rs
+++ b/dmc-lib/src/symbol.rs
@@ -4,16 +4,16 @@ use std::rc::Rc;
 
 pub struct FunctionSymbol {
     name: Rc<str>,
-    parameters: Vec<Rc<ParameterSymbol>>,
     is_platform: bool,
+    parameters: Option<Vec<Rc<RefCell<ParameterSymbol>>>>,
 }
 
 impl FunctionSymbol {
-    pub fn new(name: &str, parameters: &[Rc<ParameterSymbol>], is_platform: bool) -> Self {
+    pub fn new(name: &str, is_platform: bool) -> Self {
         Self {
             name: name.into(),
-            parameters: parameters.into(),
             is_platform,
+            parameters: None,
         }
     }
 
@@ -25,8 +25,12 @@ impl FunctionSymbol {
         self.name.clone()
     }
 
-    pub fn parameters(&self) -> &[Rc<ParameterSymbol>] {
-        &self.parameters
+    pub fn set_parameters(&mut self, parameters: Vec<Rc<RefCell<ParameterSymbol>>>) {
+        self.parameters = Some(parameters);
+    }
+
+    pub fn parameters(&self) -> &[Rc<RefCell<ParameterSymbol>>] {
+        self.parameters.as_ref().unwrap()
     }
 
     pub fn return_type(&self) -> TypeInfo {
@@ -111,7 +115,7 @@ impl VariableSymbol {
 }
 
 pub enum ExpressibleSymbol {
-    Function(Rc<FunctionSymbol>),
+    Function(Rc<RefCell<FunctionSymbol>>),
     Parameter(Rc<RefCell<ParameterSymbol>>),
     Variable(Rc<RefCell<VariableSymbol>>),
 }
diff --git a/dmc-lib/src/symbol_table.rs b/dmc-lib/src/symbol_table.rs
index 62bdfc1..4f0bd52 100644
--- a/dmc-lib/src/symbol_table.rs
+++ b/dmc-lib/src/symbol_table.rs
@@ -51,32 +51,35 @@ impl SymbolTable {
     pub fn insert_function_symbol(
         &mut self,
         function_symbol: FunctionSymbol,
-    ) -> Result<(), SymbolInsertError> {
+    ) -> Result<Rc<RefCell<FunctionSymbol>>, SymbolInsertError> {
         if self.current_scope_has_name(function_symbol.name()) {
             return Err(SymbolInsertError::AlreadyDeclared(AlreadyDeclared::new(
                 function_symbol.name(),
             )));
         }
+        let name = function_symbol.name_owned();
+        let as_rc = Rc::new(RefCell::new(function_symbol));
+
         self.current_scope_mut()
             .function_symbols_mut()
-            .insert(function_symbol.name_owned(), Rc::new(function_symbol));
-        Ok(())
+            .insert(name, as_rc.clone());
+        Ok(as_rc)
     }
 
     pub fn insert_parameter_symbol(
         &mut self,
         parameter_symbol: ParameterSymbol,
-    ) -> Result<(), SymbolInsertError> {
+    ) -> Result<Rc<RefCell<ParameterSymbol>>, SymbolInsertError> {
         if self.current_scope_has_name(parameter_symbol.name()) {
             return Err(SymbolInsertError::AlreadyDeclared(AlreadyDeclared::new(
                 parameter_symbol.name(),
             )));
         }
-        self.current_scope_mut().parameter_symbols_mut().insert(
-            parameter_symbol.name_owned(),
-            Rc::new(RefCell::new(parameter_symbol)),
-        );
-        Ok(())
+        let as_rc = Rc::new(RefCell::new(parameter_symbol));
+        self.current_scope_mut()
+            .parameter_symbols_mut()
+            .insert(as_rc.borrow().name_owned(), as_rc.clone());
+        Ok(as_rc)
     }
 
     pub fn insert_variable_symbol(
diff --git a/dmc-lib/src/token.rs b/dmc-lib/src/token.rs
index fe41073..e41ab24 100644
--- a/dmc-lib/src/token.rs
+++ b/dmc-lib/src/token.rs
@@ -36,4 +36,5 @@ pub enum TokenKind {
     LongLiteral,
     String,
     Extern,
+    Comma,
 }
diff --git a/dmc-lib/src/type_info.rs b/dmc-lib/src/type_info.rs
index 3d161e0..f3a7c0e 100644
--- a/dmc-lib/src/type_info.rs
+++ b/dmc-lib/src/type_info.rs
@@ -1,9 +1,43 @@
 use crate::symbol::FunctionSymbol;
+use std::cell::RefCell;
+use std::fmt::{Display, Formatter};
 use std::rc::Rc;
 
 #[derive(Clone)]
 pub enum TypeInfo {
     Integer,
     String,
-    Function(Rc<FunctionSymbol>),
+    Function(Rc<RefCell<FunctionSymbol>>),
+}
+
+impl Display for TypeInfo {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        let s = match self {
+            TypeInfo::Integer => "Int",
+            TypeInfo::String => "String",
+            TypeInfo::Function(_) => "fn", // todo
+        };
+        write!(f, "{}", s)
+    }
+}
+
+impl PartialEq for &TypeInfo {
+    fn eq(&self, other: &Self) -> bool {
+        match self {
+            TypeInfo::Integer => match other {
+                TypeInfo::Integer => true,
+                _ => false,
+            },
+            TypeInfo::String => match other {
+                TypeInfo::String => true,
+                _ => false,
+            },
+            TypeInfo::Function(f0) => match other {
+                TypeInfo::Function(f1) => {
+                    f0.as_ptr() == f1.as_ptr() // todo
+                }
+                _ => false,
+            },
+        }
+    }
 }
diff --git a/dvm-lib/src/instruction.rs b/dvm-lib/src/instruction.rs
index 1e0b26e..e9deecf 100644
--- a/dvm-lib/src/instruction.rs
+++ b/dvm-lib/src/instruction.rs
@@ -3,6 +3,7 @@ use std::rc::Rc;
 pub type Register = usize;
 pub type ConstantName = Rc<str>;
 pub type FunctionName = Rc<str>;
+pub type ArgCount = usize;
 
 pub enum Instruction {
     MoveRegister(Register, Register),
@@ -13,7 +14,7 @@ pub enum Instruction {
     PushInt(i32),
     PushStackFrameOffset(isize),
 
-    InvokePlatformStatic(FunctionName),
+    InvokePlatformStatic(FunctionName, ArgCount),
 
     LoadStringConstant(ConstantName, Register),
 
diff --git a/dvm-lib/src/lib.rs b/dvm-lib/src/lib.rs
index b7c1352..88c25a3 100644
--- a/dvm-lib/src/lib.rs
+++ b/dvm-lib/src/lib.rs
@@ -1,2 +1,3 @@
 pub mod instruction;
+pub mod platform_function;
 pub mod vm;
diff --git a/dvm-lib/src/platform_function.rs b/dvm-lib/src/platform_function.rs
new file mode 100644
index 0000000..4666fac
--- /dev/null
+++ b/dvm-lib/src/platform_function.rs
@@ -0,0 +1,6 @@
+use crate::vm::value::Value;
+use crate::vm::{DvmContext, DvmState};
+use std::error::Error;
+
+pub type PlatformFunction =
+    fn(context: &DvmContext, state: &DvmState, args: &[Value]) -> Result<Value, Box<dyn Error>>;
diff --git a/dvm-lib/src/vm/mod.rs b/dvm-lib/src/vm/mod.rs
index d2d1cb4..e37cfb0 100644
--- a/dvm-lib/src/vm/mod.rs
+++ b/dvm-lib/src/vm/mod.rs
@@ -1,4 +1,5 @@
 use crate::instruction::Instruction;
+use crate::platform_function::PlatformFunction;
 use crate::vm::constant::Constant;
 use crate::vm::function::Function;
 use crate::vm::value::Value;
@@ -11,6 +12,7 @@ pub mod value;
 
 pub struct DvmContext {
     functions: HashMap<Rc<str>, Function>,
+    platform_functions: HashMap<Rc<str>, PlatformFunction>,
     constants: HashMap<Rc<str>, Constant>,
 }
 
@@ -18,10 +20,27 @@ impl DvmContext {
     pub fn new() -> Self {
         Self {
             functions: HashMap::new(),
+            platform_functions: HashMap::new(),
             constants: HashMap::new(),
         }
     }
 
+    pub fn functions(&self) -> &HashMap<Rc<str>, Function> {
+        &self.functions
+    }
+
+    pub fn functions_mut(&mut self) -> &mut HashMap<Rc<str>, Function> {
+        &mut self.functions
+    }
+
+    pub fn platform_functions(&self) -> &HashMap<Rc<str>, PlatformFunction> {
+        &self.platform_functions
+    }
+
+    pub fn platform_functions_mut(&mut self) -> &mut HashMap<Rc<str>, PlatformFunction> {
+        &mut self.platform_functions
+    }
+
     pub fn add_function(&mut self, function: Function) {
         self.functions.insert(function.name_owned(), function);
     }
@@ -155,10 +174,28 @@ pub fn call(
             }
 
             /* Invoke instructions */
-            Instruction::InvokePlatformStatic(function_name) => {
-                if function_name.as_ref() == "println" {
-                    println!("{:?}", state.stack());
-                    println!("{:?}", state.registers());
+            Instruction::InvokePlatformStatic(function_name, arg_count) => {
+                let stack = state.stack();
+                let args = &stack[stack.len() - arg_count..];
+                let platform_function = context
+                    .platform_functions()
+                    .get(function_name)
+                    .expect(&format!("Platform function {} not found", function_name));
+                let result = platform_function(context, state, args);
+                match result {
+                    Ok(return_value) => {
+                        // pop args off the stack
+                        let mut i: usize = 0;
+                        while i < *arg_count {
+                            state.stack_mut().pop();
+                            i += 1;
+                        }
+                        state.stack_mut().push(return_value);
+                    }
+                    Err(error) => {
+                        // Eventually we will have some kind of exception handling
+                        panic!("{}", error);
+                    }
                 }
             }
 
@@ -183,5 +220,5 @@ pub fn call(
         }
         state.increment_ip();
     }
-    None
+    None // todo: returning results from main functions
 }
diff --git a/examples/hello.dm b/examples/hello.dm
index 84cb693..ed2a17f 100644
--- a/examples/hello.dm
+++ b/examples/hello.dm
@@ -1,4 +1,4 @@
-extern fn println()
+extern fn println(message)
 
 fn main()
     let x = "Hello, World!"