diff --git a/README.markdown b/README.markdown
index 55877a5..9ffcd27 100644
--- a/README.markdown
+++ b/README.markdown
@@ -33,9 +33,7 @@ TODO
 
 For 0.3:
 
-*   extern routines.
 *   generate 6502 code for all SixtyPical instructions.
-*   a little demo that actually compiles and does something on a C64 emulator.
 
 For 0.4:
 
diff --git a/bin/sixtypical b/bin/sixtypical
index 3ff56bb..03013b5 100755
--- a/bin/sixtypical
+++ b/bin/sixtypical
@@ -21,7 +21,7 @@ from sixtypical.parser import Parser
 from sixtypical.evaluator import eval_program
 from sixtypical.analyzer import analyze_program
 from sixtypical.emitter import Emitter, Byte, Word
-from sixtypical.compiler import compile_program
+from sixtypical.compiler import Compiler
 
 
 if __name__ == '__main__':
@@ -75,7 +75,8 @@ if __name__ == '__main__':
             emitter.emit(Word(start_addr))
             for byte in header:
                 emitter.emit(Byte(byte))
-            compile_program(program, emitter)
+            compiler = Compiler(emitter)
+            compiler.compile_program(program)
             if options.debug:
                 print repr(emitter.accum)
             else:
diff --git a/eg/print.60p b/eg/print.60p
new file mode 100644
index 0000000..c1c29c3
--- /dev/null
+++ b/eg/print.60p
@@ -0,0 +1,12 @@
+routine chrout
+  inputs a
+  trashes a
+  @ 65490
+
+routine main
+  inputs a
+  trashes a, z, n
+{
+    ld a, 65
+    call chrout
+}
diff --git a/src/sixtypical/compiler.py b/src/sixtypical/compiler.py
index 240fdcf..df83c54 100644
--- a/src/sixtypical/compiler.py
+++ b/src/sixtypical/compiler.py
@@ -5,10 +5,10 @@ from sixtypical.model import (
     ConstantRef, LocationRef,
     REG_A, REG_X, REG_Y, FLAG_Z, FLAG_N, FLAG_V, FLAG_C
 )
-from sixtypical.emitter import Byte
+from sixtypical.emitter import Label, Byte
 from sixtypical.gen6502 import (
     Immediate, Absolute,
-    LDA, LDX, LDY, STA, STX, STY, CLC, SEC, ADC, RTS
+    LDA, LDX, LDY, STA, STX, STY, CLC, SEC, ADC, RTS, JSR
 )
 
 
@@ -16,90 +16,97 @@ class UnsupportedOpcodeError(KeyError):
     pass
 
 
-def compile_program(program, emitter):
-    assert isinstance(program, Program)
-    routines = {r.name: r for r in program.routines}
-    for routine in program.routines:
-        compile_routine(routine, emitter, routines)
+class Compiler(object):
+    def __init__(self, emitter):
+        self.emitter = emitter
+        self.routines = {}
+        self.labels = {}
 
+    def compile_program(self, program):
+        assert isinstance(program, Program)
+        for routine in program.routines:
+            self.routines[routine.name] = routine
+            label = Label(routine.name)
+            if routine.addr is not None:
+                label.set_addr(routine.addr)
+            self.labels[routine.name] = label
+        for routine in program.routines:
+            self.compile_routine(routine)
 
-def compile_routine(routine, emitter, routines):
-    assert isinstance(routine, Routine)
-    label = emitter.make_label(routine.name)
-    if routine.block:
-        compile_block(routine.block, emitter, routines)
-        emitter.emit(RTS())
-    return label
+    def compile_routine(self, routine):
+        assert isinstance(routine, Routine)
+        if routine.block:
+            self.compile_block(routine.block)
+            self.emitter.emit(RTS())
 
+    def compile_block(self, block):
+        assert isinstance(block, Block)
+        label = self.emitter.make_label()
+        for instr in block.instrs:
+            self.compile_instr(instr)
+        return label
 
-def compile_block(block, emitter, routines):
-    assert isinstance(block, Block)
-    label = emitter.make_label()
-    for instr in block.instrs:
-        compile_instr(instr, emitter, routines)
-    return label
-
-
-def compile_instr(instr, emitter, routines):
-    assert isinstance(instr, Instr)
-    opcode = instr.opcode
-    dest = instr.dest
-    src = instr.src
-
-    if opcode == 'ld':
-        if dest == REG_A:
-            if isinstance(src, ConstantRef):
-                emitter.emit(LDA(Immediate(Byte(src.value))))
+    def compile_instr(self, instr):
+        assert isinstance(instr, Instr)
+        opcode = instr.opcode
+        dest = instr.dest
+        src = instr.src
+    
+        if opcode == 'ld':
+            if dest == REG_A:
+                if isinstance(src, ConstantRef):
+                    self.emitter.emit(LDA(Immediate(Byte(src.value))))
+                else:
+                    self.emitter.emit(LDA(Absolute(src.label)))
+            elif dest == REG_X:
+                pass
+            elif dest == REG_Y:
+                pass
             else:
-                emitter.emit(LDA(Absolute(src.label)))
-        elif dest == REG_X:
-            pass
-        elif dest == REG_Y:
-            pass
-        else:
-            raise UnsupportedOpcodeError(instr)
-    elif opcode == 'st':
-        if dest == FLAG_C and src == ConstantRef(0):
-            emitter.emit(CLC())
-        elif dest == FLAG_C and src == ConstantRef(1):
-            emitter.emit(SEC())
-        elif src == REG_A:
-            emitter.emit(STA(Absolute(dest.label)))
-        elif src == REG_X:
-            emitter.emit(STX(Absolute(dest.label)))
-        elif src == REG_Y:
-            emitter.emit(STY(Absolute(dest.label)))
-        else:
-            raise UnsupportedOpcodeError(instr)
-    elif opcode == 'add':
-        if dest == REG_A:
-            if isinstance(src, ConstantRef):
-                emitter.emit(ADC(Immediate(Byte(src.value))))
+                raise UnsupportedOpcodeError(instr)
+        elif opcode == 'st':
+            if dest == FLAG_C and src == ConstantRef(0):
+                self.emitter.emit(CLC())
+            elif dest == FLAG_C and src == ConstantRef(1):
+                self.emitter.emit(SEC())
+            elif src == REG_A:
+                self.emitter.emit(STA(Absolute(dest.label)))
+            elif src == REG_X:
+                self.emitter.emit(STX(Absolute(dest.label)))
+            elif src == REG_Y:
+                self.emitter.emit(STY(Absolute(dest.label)))
             else:
-                emitter.emit(ADC(Absolute(src.label)))
+                raise UnsupportedOpcodeError(instr)
+        elif opcode == 'add':
+            if dest == REG_A:
+                if isinstance(src, ConstantRef):
+                    self.emitter.emit(ADC(Immediate(Byte(src.value))))
+                else:
+                    self.emitter.emit(ADC(Absolute(src.label)))
+            else:
+                raise UnsupportedOpcodeError(instr)
+        elif opcode == 'sub':
+            raise NotImplementedError
+        elif opcode == 'inc':
+            raise NotImplementedError
+        elif opcode == 'dec':
+            raise NotImplementedError
+        elif opcode == 'cmp':
+            raise NotImplementedError
+        elif opcode == 'and':
+            raise NotImplementedError
+        elif opcode == 'or':
+            raise NotImplementedError
+        elif opcode == 'xor':
+            raise NotImplementedError
+        elif opcode == 'shl':
+            raise NotImplementedError
+        elif opcode == 'shr':
+            raise NotImplementedError
+        elif opcode == 'call':
+            label = self.labels[instr.name]
+            self.emitter.emit(JSR(Absolute(label)))
+        elif opcode == 'if':
+            raise NotImplementedError
         else:
-            raise UnsupportedOpcodeError(instr)
-    elif opcode == 'sub':
-        raise NotImplementedError
-    elif opcode == 'inc':
-        raise NotImplementedError
-    elif opcode == 'dec':
-        raise NotImplementedError
-    elif opcode == 'cmp':
-        raise NotImplementedError
-    elif opcode == 'and':
-        raise NotImplementedError
-    elif opcode == 'or':
-        raise NotImplementedError
-    elif opcode == 'xor':
-        raise NotImplementedError
-    elif opcode == 'shl':
-        raise NotImplementedError
-    elif opcode == 'shr':
-        raise NotImplementedError
-    elif opcode == 'call':
-        raise NotImplementedError(instr.name)
-    elif opcode == 'if':
-        raise NotImplementedError
-    else:
-        raise NotImplementedError
+            raise NotImplementedError
diff --git a/src/sixtypical/emitter.py b/src/sixtypical/emitter.py
index f4dc0eb..e50ef7b 100644
--- a/src/sixtypical/emitter.py
+++ b/src/sixtypical/emitter.py
@@ -58,6 +58,10 @@ class Label(Emittable):
         assert self.addr is not None, "unresolved label: %s" % self.name
         return Word(self.addr).serialize()
 
+    def __repr__(self):
+        addrs = ', addr=%r' % self.addr if self.addr is not None else ''
+        return "%s(%r%s)" % (self.__class__.__name__, self.name, addrs)
+
 
 class Emitter(object):
     def __init__(self, addr):
diff --git a/src/sixtypical/gen6502.py b/src/sixtypical/gen6502.py
index fc9b5cd..381d6f1 100644
--- a/src/sixtypical/gen6502.py
+++ b/src/sixtypical/gen6502.py
@@ -123,6 +123,12 @@ class INY(Opcode):
     }
 
 
+class JSR(Opcode):
+    opcodes = {
+        Absolute:  0x20,
+    }
+
+
 class LDA(Opcode):
     opcodes = {
         Immediate: 0xa9,
diff --git a/tests/SixtyPical Compilation.md b/tests/SixtyPical Compilation.md
index 09327c7..5d5c26b 100644
--- a/tests/SixtyPical Compilation.md	
+++ b/tests/SixtyPical Compilation.md	
@@ -44,4 +44,4 @@ Call extern.
     |     ld a, 65
     |     call chrout
     | }
-    = 00c018690460
+    = 00c0a94120d2ff60