diff --git a/go/asm/asm.go b/go/asm/asm.go
index fdec70a..88ea8ae 100644
--- a/go/asm/asm.go
+++ b/go/asm/asm.go
@@ -1,8 +1,11 @@
 package asm
 
 import (
+	"bytes"
+	"encoding/binary"
 	"fmt"
 	"io"
+	"math"
 	"strings"
 
 	"github.com/alecthomas/participle/v2"
@@ -25,15 +28,15 @@ func(d Display) String() string {
 	return fmt.Sprintf("Display: %v %v", d.Sym, d.Val)
 }
 
-type Sig struct {
-	Sym string `@Sym Whitespace`
-	Size uint32 `@Size Whitespace`
-	Val uint32 `@Size Whitespace`
-}
-
-func(s Sig) String() string {
-	return fmt.Sprintf("Sig: %v %v %v", s.Sym, s.Size, s.Val)
-}
+//type Sig struct {
+//	Sym string `@Sym Whitespace`
+//	Size uint32 `@Size Whitespace`
+//	Val uint32 `@Size Whitespace`
+//}
+//
+//func(s Sig) String() string {
+//	return fmt.Sprintf("Sig: %v %v %v", s.Sym, s.Size, s.Val)
+//}
 
 type Single struct {
 	One string `@Sym Whitespace`
@@ -111,12 +114,90 @@ var (
 	)
 )
 
+func numSize(n uint32) int {
+	v := math.Log2(float64(n))
+	return int(((v - 1) / 8) + 1)
+}
+
+func writeOpcode(op vm.Opcode, w *bytes.Buffer) (int, error) {
+	bn := [2]byte{}
+	binary.BigEndian.PutUint16(bn[:], uint16(op))
+	n, err := w.Write(bn[:])
+	return n, err
+}
+
+func writeSym(s string, w *bytes.Buffer) (int, error) {
+	sz := len(s)
+	if sz > 255 {
+		return 0, fmt.Errorf("string size %v too big", sz)
+	}
+	w.Write([]byte{byte(sz)})
+	return w.WriteString(s)
+}
+
+func writeSize(n uint32, w *bytes.Buffer) (int, error) {
+	bn := [4]byte{}
+	sz := numSize(n)
+	if sz > 4 {
+		return 0, fmt.Errorf("number size %v too big", sz)
+	}
+	w.Write([]byte{byte(sz)})
+	binary.BigEndian.PutUint32(bn[:], n)
+	c := 4-sz
+	return w.Write(bn[c:])	
+}
+
+
+func parseSized(op vm.Opcode, arg Arg, w io.Writer) (int, error) {
+	var rn int
+
+	v := arg.ArgSized
+	if v == nil {
+		return 0, nil
+	}
+
+	b := bytes.NewBuffer(nil)
+
+	n, err := writeOpcode(op, b)
+	rn += n
+	if  err != nil {
+		return rn, err
+	}
+	
+	n, err = writeSym(v.Sym, b)
+	rn += n
+	if err != nil {
+		return rn, err
+	}
+
+	n, err = writeSize(v.Size, b)
+	rn += n
+	if err != nil {
+		return rn, err
+	}
+	if w != nil {
+		rn, err = w.Write(b.Bytes())
+	} else {
+		rn = 0
+	}
+	return rn, err
+}
+
 func Parse(s string, w io.Writer) (int, error) {
 	rd := strings.NewReader(s)
 	ast, err := asmParser.Parse("file", rd)
-	for i, v := range ast.Instructions {
+	var rn int
+
+	for _, v := range ast.Instructions {
 		op := vm.OpcodeIndex[v.OpCode]
-		fmt.Printf("%v (%v) %v\n", i, op, v)
+		n, err := parseSized(op, v.OpArg, w)
+		if err != nil {
+			return n, err
+		}
+		if n > 0 {
+			rn += n
+			continue
+		}
 	}
-	return 0, err
+	return rn, err
 }
diff --git a/go/asm/asm_test.go b/go/asm/asm_test.go
index 83ed58f..0c4b030 100644
--- a/go/asm/asm_test.go
+++ b/go/asm/asm_test.go
@@ -1,6 +1,7 @@
 package asm
 
 import (
+	"bytes"
 	"log"
 	"testing"
 
@@ -16,6 +17,7 @@ func TestParserInit(t *testing.T) {
 	b = vm.NewLine(b, vm.MOUT, []string{"bar", "barbarbaz"}, nil, nil)
 	s, err := vm.ToString(b)
 	log.Printf("parsing:\n%s\n", s)
+
 	n, err := Parse(s, nil)
 	if err != nil {
 		t.Fatal(err)
@@ -24,3 +26,23 @@ func TestParserInit(t *testing.T) {
 		t.Fatalf("expected 0 byte write count, got %v", n)
 	}
 }
+
+func TestParserSized(t *testing.T) {
+	var b []byte
+	b = vm.NewLine(b, vm.LOAD, []string{"foo"}, []byte{42}, nil)
+	s, err := vm.ToString(b)
+	log.Printf("parsing:\n%s\n", s)
+
+	r := bytes.NewBuffer(nil)
+	n, err := Parse(s, r)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if n != 8 {
+		t.Fatalf("expected 0 byte write count, got %v", n)
+	}
+	rb := r.Bytes()
+	if !bytes.Equal(rb, []byte{0x00, vm.LOAD, 0x03, 0x66, 0x6f, 0x6f, 0x01, 0x2a}) {
+		t.Fatalf("expected 0x00%x012a, got %v", vm.LOAD, rb)
+	}
+}