diff --git a/README.md b/README.md
index 52fe4c6..62be69c 100644
--- a/README.md
+++ b/README.md
@@ -47,8 +47,8 @@ Current disk operations supported:
 | ---------------- | -------- | ------ | ------------------ |
 | basic structures | ✓        | ✓      | ✓                  |
 | ls               | ✓        | ✓      | ✓                  |
-| dump             | ✓        | ✗      | ✓                  |
-| put              | ✗        | ✗      | ✓                  |
+| dump             | ✗        | ✗      | ✗                  |
+| put              | ✗        | ✗      | ✗                  |
 | dumptext         | ✗        | ✗      | ✗                  |
 | delete           | ✗        | ✗      | ✗                  |
 | rename           | ✗        | ✗      | ✗                  |
@@ -78,12 +78,9 @@ will be likely to get priority.
 - [x] Implement `GetFile` for DOS 3.3
 - [ ] Add and implement the `-l` flag for `ls`
 - [x] Add `Delete` to the `disk.Operator` interface
-  - [x] Implement it for Super-Mon
+  - [ ] Implement it for Super-Mon
   - [ ] Implement it for DOS 3.3
-- [ ] Make 13-sector DOS disks work
-- [ ] Read/write nybble formats
-- [ ] Read/write gzipped files
-- [ ] Add basic ProDOS structures
+- [x] Add basic ProDOS structures
 - [ ] Add ProDOS support
 
 # Related tools
@@ -114,38 +111,34 @@ will be likely to get priority.
 
 - `.do`
 - `.po`
-- `.dsk` - could be DO or PO.
+- `.dsk` - could be DO or PO. When in doubt, assume DO.
 
-DOS 3.2.1: the 13 sectors are physically skewed on disk.
-
-DOS 3.3+: the 16 physical sectors are stored in ascending order on disk, not physically skewed at all. The 
-
-
-| Logical Sector  | DOS 3.3 Physical Sector | ProDOS Physical Sector |
-| --------------- | -------------- | ------------- |
-| 0 | 0 | x |
-| 1 | D | x | 
-| 2 | B | x | 
-| 3 | 9 | x | 
-| 4 | 7 | x | 
-| 5 | 5 | x | 
-| 6 | 3 | x | 
-| 7 | 1 | x | 
-| 8 | E | x | 
-| 9 | C | x | 
-| A | A | x | 
-| B | 8 | x | 
-| C | 6 | x | 
-| D | 4 | x | 
-| E | 2 | x | 
-| F | F | x | 
+| Physical Sectors | DOS 3.2 Logical | DOS 3.3 Logical | ProDOS/Pascal Logical | CP/M Logical |
+|------------------|-----------------|-----------------|-----------------------|------------- |
+|        0         |        0        |        0        |          0.0          |      0.0     |
+|        1         |        1        |        7        |          4.0          |      2.3     |
+|        2         |        2        |        E        |          0.1          |      1.2     |
+|        3         |        3        |        6        |          4.1          |      0.1     |
+|        4         |        4        |        D        |          1.0          |      3.0     |
+|        5         |        5        |        5        |          5.0          |      1.3     |
+|        6         |        6        |        C        |          1.1          |      0.2     |
+|        7         |        7        |        4        |          5.1          |      3.1     |
+|        8         |        8        |        B        |          2.0          |      2.0     |
+|        9         |        9        |        3        |          6.0          |      0.3     |
+|        A         |        A        |        A        |          2.1          |      3.2     |
+|        B         |        B        |        2        |          6.1          |      2.1     |
+|        C         |        C        |        9        |          3.0          |      1.0     |
+|        D         |                 |        1        |          7.0          |      3.3     |
+|        E         |                 |        8        |          3.1          |      2.2     |
+|        F         |                 |        F        |          7.1          |      1.1     |
 
+_Note: DOS 3.2 rearranged the physical sectors on disk to achieve interleaving._
 ### RWTS - DOS
 
 Sector mapping:
 http://www.textfiles.com/apple/ANATOMY/rwts.s.txt and search for INTRLEAV
 
-Mapping from specified sector to physical sector (the reverse of what the comment says):
+Mapping from specified sector to physical sector:
 
 `00 0D 0B 09 07 05 03 01 0E 0C 0A 08 06 04 02 0F`
 
diff --git a/cmd/catalog.go b/cmd/catalog.go
index 8204622..ba4c9b1 100644
--- a/cmd/catalog.go
+++ b/cmd/catalog.go
@@ -10,19 +10,19 @@ import (
 	"github.com/zellyn/diskii/types"
 )
 
-var shortnames bool // flag for whether to print short filenames
-var debug bool
-
 type LsCmd struct {
+	Order  string `kong:"default='auto',enum='auto,do,po',help='Logical-to-physical sector order.'"`
+	System string `kong:"default='auto',enum='auto,dos3',help='DOS system used for image.'"`
+
 	ShortNames bool     `kong:"short='s',help='Whether to print short filenames (only makes a difference on Super-Mon disks).'"`
 	Image      *os.File `kong:"arg,required,help='Disk/device image to read.'"`
 	Directory  string   `kong:"arg,optional,help='Directory to list (ProDOS only).'"`
 }
 
 func (l *LsCmd) Run(globals *types.Globals) error {
-	op, order, err := disk.OpenImage(l.Image, globals)
+	op, order, err := disk.OpenImage(l.Image, l.Order, l.System, globals)
 	if err != nil {
-		return err
+		return fmt.Errorf("%w: %s", err, l.Image.Name())
 	}
 	if globals.Debug {
 		fmt.Fprintf(os.Stderr, "Opened disk with order %q, system %q\n", order, op.Name())
@@ -38,7 +38,7 @@ func (l *LsCmd) Run(globals *types.Globals) error {
 		return err
 	}
 	for _, fd := range fds {
-		if !shortnames && fd.Fullname != "" {
+		if !l.ShortNames && fd.Fullname != "" {
 			fmt.Println(fd.Fullname)
 		} else {
 			fmt.Println(fd.Name)
diff --git a/cmd/reorder.go b/cmd/reorder.go
new file mode 100644
index 0000000..9cc04b2
--- /dev/null
+++ b/cmd/reorder.go
@@ -0,0 +1,101 @@
+package cmd
+
+import (
+	"fmt"
+	"path"
+	"strings"
+
+	"github.com/zellyn/diskii/disk"
+	"github.com/zellyn/diskii/helpers"
+	"github.com/zellyn/diskii/types"
+)
+
+type ReorderCmd struct {
+	Order    string `kong:"default='auto',enum='auto,do,po',help='Logical-to-physical sector order.'"`
+	NewOrder string `kong:"default='auto',enum='auto,do,po',help='New Logical-to-physical sector order.'"`
+	Force    bool   `kong:"short='s',help='Overwrite existing file?'"`
+
+	DiskImage    string `kong:"arg,required,type='existingfile',help='Disk image to read.'"`
+	NewDiskImage string `kong:"arg,optional,type='path',help='Disk image to write, if different.'"`
+}
+
+func (r *ReorderCmd) Run(globals *types.Globals) error {
+	fromOrderName, toOrderName, err := getOrders(r.DiskImage, r.Order, r.NewDiskImage, r.NewOrder)
+	if err != nil {
+		return err
+	}
+	frombytes, err := helpers.FileContentsOrStdIn(r.DiskImage)
+	if err != nil {
+		return err
+	}
+	fromOrder, ok := disk.LogicalToPhysicalByName[fromOrderName]
+	if !ok {
+		return fmt.Errorf("internal error: disk order '%s' not found", fromOrderName)
+	}
+	toOrder, ok := disk.PhysicalToLogicalByName[toOrderName]
+	if !ok {
+		return fmt.Errorf("internal error: disk order '%s' not found", toOrderName)
+	}
+	rawbytes, err := disk.Swizzle(frombytes, fromOrder)
+	if err != nil {
+		return err
+	}
+	tobytes, err := disk.Swizzle(rawbytes, toOrder)
+	if err != nil {
+		return err
+	}
+	return helpers.WriteOutput(r.NewDiskImage, tobytes, r.DiskImage, r.Force)
+}
+
+// getOrders returns the input order, and the output order.
+func getOrders(inFilename string, inOrder string, outFilename string, outOrder string) (string, string, error) {
+	if inOrder == "auto" && outOrder != "auto" {
+		return oppositeOrder(outOrder), outOrder, nil
+	}
+	if outOrder == "auto" && inOrder != "auto" {
+		return inOrder, oppositeOrder(inOrder), nil
+	}
+	if inOrder != outOrder {
+		return inOrder, outOrder, nil
+	}
+	if inOrder != "auto" {
+		return "", "", fmt.Errorf("identical order and new-order")
+	}
+
+	inGuess, outGuess := orderFromFilename(inFilename), orderFromFilename(outFilename)
+	if inGuess == outGuess {
+		if inGuess == "" {
+			return "", "", fmt.Errorf("cannot determine input or output order from file extensions")
+		}
+		return "", "", fmt.Errorf("guessed order (%s) from file %q is the same as guessed order (%s) from file %q", inGuess, inFilename, outGuess, outFilename)
+	}
+
+	if inGuess == "" {
+		return oppositeOrder(outGuess), outGuess, nil
+	}
+	if outGuess == "" {
+		return inGuess, oppositeOrder(inGuess), nil
+	}
+	return inGuess, outGuess, nil
+}
+
+// oppositeOrder returns the opposite order from the input.
+func oppositeOrder(order string) string {
+	if order == "do" {
+		return "po"
+	}
+	return "do"
+}
+
+// orderFromFilename tries to guess the disk order from the filename, using the extension.
+func orderFromFilename(filename string) string {
+	ext := strings.ToLower(path.Ext(filename))
+	switch ext {
+	case ".dsk", ".do":
+		return "do"
+	case ".po":
+		return "po"
+	default:
+		return ""
+	}
+}
diff --git a/data/data.go b/data/data.go
index f14b74e..6f035e5 100644
--- a/data/data.go
+++ b/data/data.go
@@ -3,16 +3,20 @@ package data
 import _ "embed"
 
 // DOS 3.3 Master Disk.
-//go:embed disks/dos33mst.dsk
+//go:embed disks/dos33master.dsk
 var DOS33master_dsk []byte
 
+// DOS 3.3 Master Disk, as a .woz file.
+//go:embed disks/dos33master.woz
+var DOS33master_woz []byte
+
 // John Brooks' update to ProDOS.
 // Website: https://prodos8.com
 // Announcements: https://www.callapple.org/author/jbrooks/
-//go:embed disks/ProDOS_2_4_2.dsk
-var ProDOS242_dsk []byte
+//go:embed disks/ProDOS_2_4_2.po
+var ProDOS242_po []byte
 
-// The new ProDOS sector 0, used on and after the IIGS System 4.0.
+// The new ProDOS sector 0, used on and after the IIGS System 4.0. Understands sparse PRODOS.SYSTEM files.
 //go:embed boot/prodos-new-boot0.bin
 var ProDOSNewBootSector0 []byte
 
diff --git a/data/disks/ProDOS_2_4_1.dsk b/data/disks/ProDOS_2_4_1.dsk
deleted file mode 100644
index ef4e8b1..0000000
Binary files a/data/disks/ProDOS_2_4_1.dsk and /dev/null differ
diff --git a/data/disks/ProDOS_2_4_2.dsk b/data/disks/ProDOS_2_4_2.dsk
deleted file mode 100644
index 6530d52..0000000
Binary files a/data/disks/ProDOS_2_4_2.dsk and /dev/null differ
diff --git a/data/disks/ProDOS_2_4_2.po b/data/disks/ProDOS_2_4_2.po
new file mode 100644
index 0000000..019e252
Binary files /dev/null and b/data/disks/ProDOS_2_4_2.po differ
diff --git a/data/disks/dos33mst.dsk b/data/disks/Super-Mon-2.0.dsk
similarity index 51%
rename from data/disks/dos33mst.dsk
rename to data/disks/Super-Mon-2.0.dsk
index ef257aa..badfd82 100644
Binary files a/data/disks/dos33mst.dsk and b/data/disks/Super-Mon-2.0.dsk differ
diff --git a/data/disks/dos33mst-incorrect-suffix.po b/data/disks/dos33master.dsk
similarity index 100%
rename from data/disks/dos33mst-incorrect-suffix.po
rename to data/disks/dos33master.dsk
diff --git a/disk/dev.go b/disk/dev.go
index 5e1205f..4c3f7c0 100644
--- a/disk/dev.go
+++ b/disk/dev.go
@@ -11,7 +11,7 @@ import (
 )
 
 // A ProDOS block.
-type Block [256]byte
+type Block [512]byte
 
 // Dev represents a .po disk image.
 type Dev struct {
diff --git a/disk/disk.go b/disk/disk.go
index 74c667d..fde6565 100644
--- a/disk/disk.go
+++ b/disk/disk.go
@@ -41,6 +41,20 @@ var ProDosPhysicalToLogicalSectorMap = []int{
 	0x04, 0x0C, 0x05, 0x0D, 0x06, 0x0E, 0x07, 0x0F,
 }
 
+// LogicalToPhysicalByName maps from "do" and "po" to the corresponding
+// logical-to-physical ordering.
+var LogicalToPhysicalByName map[string][]int = map[string][]int{
+	"do": Dos33LogicalToPhysicalSectorMap,
+	"po": ProDOSLogicalToPhysicalSectorMap,
+}
+
+// PhysicalToLogicalByName maps from "do" and "po" to the corresponding
+// physical-to-logical ordering.
+var PhysicalToLogicalByName map[string][]int = map[string][]int{
+	"do": Dos33PhysicalToLogicalSectorMap,
+	"po": ProDosPhysicalToLogicalSectorMap,
+}
+
 // TrackSector is a pair of track/sector bytes.
 type TrackSector struct {
 	Track  byte
diff --git a/disk/open.go b/disk/open.go
index ba65ce0..34de3c9 100644
--- a/disk/open.go
+++ b/disk/open.go
@@ -10,36 +10,30 @@ import (
 	"github.com/zellyn/diskii/types"
 )
 
-var diskOrdersByName map[string][]int = map[string][]int{
-	"do":  Dos33LogicalToPhysicalSectorMap,
-	"po":  ProDOSLogicalToPhysicalSectorMap,
-	"raw": {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0xA, 0xB, 0xC, 0xD, 0xE, 0xF},
-}
-
 // OpenImage attempts to open an image on disk, using the provided ordering and system type.
-func OpenImage(file *os.File, globals *types.Globals) (types.Operator, string, error) {
+func OpenImage(file *os.File, order string, system string, globals *types.Globals) (types.Operator, string, error) {
 	bb, err := io.ReadAll(file)
 	if err != nil {
 		return nil, "", err
 	}
 	if len(bb) == FloppyDiskBytes {
-		return openDoOrPo(bb, globals, strings.ToLower(path.Ext(file.Name())))
+		return openDoOrPo(bb, order, system, globals, strings.ToLower(path.Ext(file.Name())))
 	}
 	return nil, "", fmt.Errorf("OpenImage not implemented yet for non-disk-sized images")
 }
 
-func openDoOrPo(diskbytes []byte, globals *types.Globals, ext string) (types.Operator, string, error) {
+func openDoOrPo(diskbytes []byte, order string, system string, globals *types.Globals, ext string) (types.Operator, string, error) {
 	var factories []types.OperatorFactory
 	for _, factory := range globals.DiskOperatorFactories {
-		if globals.System == "auto" || globals.System == factory.Name() {
+		if system == "auto" || system == factory.Name() {
 			factories = append(factories, factory)
 		}
 	}
 	if len(factories) == 0 {
-		return nil, "", fmt.Errorf("cannot find disk system with name %q", globals.System)
+		return nil, "", fmt.Errorf("cannot find disk system with name %q", system)
 	}
-	orders := []string{globals.Order}
-	switch globals.Order {
+	orders := []string{order}
+	switch order {
 	case "do", "po":
 		// nothing more
 	case "auto":
@@ -54,16 +48,16 @@ func openDoOrPo(diskbytes []byte, globals *types.Globals, ext string) (types.Ope
 			return nil, "", fmt.Errorf("unknown disk image extension: %q", ext)
 		}
 	default:
-		return nil, "", fmt.Errorf("disk order %q invalid for %d-byte disk images", globals.Order, FloppyDiskBytes)
+		return nil, "", fmt.Errorf("disk order %q invalid for %d-byte disk images", order, FloppyDiskBytes)
 	}
 
 	for _, order := range orders {
-		swizzled, err := Swizzle(diskbytes, diskOrdersByName[order])
+		swizzled, err := Swizzle(diskbytes, LogicalToPhysicalByName[order])
 		if err != nil {
 			return nil, "", err
 		}
 		for _, factory := range factories {
-			if len(orders) == 1 && globals.System != "auto" {
+			if len(orders) == 1 && system != "auto" {
 				if globals.Debug {
 					fmt.Fprintf(os.Stderr, "Attempting to open with order=%s, system=%s.\n", order, factory.Name())
 				}
@@ -88,14 +82,14 @@ func openDoOrPo(diskbytes []byte, globals *types.Globals, ext string) (types.Ope
 			}
 		}
 	}
-	return nil, "", fmt.Errorf("openDoOrPo not implemented yet")
+	return nil, "", fmt.Errorf("unabled to open disk image")
 }
 
 // Swizzle changes the sector ordering according to the order parameter. If
 // order is nil, it leaves the order unchanged.
 func Swizzle(diskimage []byte, order []int) ([]byte, error) {
 	if len(diskimage) != FloppyDiskBytes {
-		return nil, fmt.Errorf("swizzling only works on disk images of %d bytes; got %d", FloppyDiskBytes, len(diskimage))
+		return nil, fmt.Errorf("reordering only works on disk images of %d bytes; got %d", FloppyDiskBytes, len(diskimage))
 	}
 	if err := validateOrder(order); err != nil {
 		return nil, fmt.Errorf("called Swizzle with weird order: %w", err)
diff --git a/dos3/dos3.go b/dos3/dos3.go
index a0d1e60..f10fcda 100644
--- a/dos3/dos3.go
+++ b/dos3/dos3.go
@@ -7,7 +7,6 @@ package dos3
 import (
 	"encoding/binary"
 	"fmt"
-	"os"
 	"strings"
 
 	"github.com/zellyn/diskii/disk"
@@ -500,9 +499,6 @@ func readCatalogSectors(diskbytes []byte, debug bool) ([]CatalogSector, error) {
 	if err := v.Validate(); err != nil {
 		return nil, fmt.Errorf("Invalid VTOC sector: %v", err)
 	}
-	if debug {
-		fmt.Fprintf(os.Stderr, "Read VTOC sector: %#v\n", v)
-	}
 
 	nextTrack := v.CatalogTrack
 	nextSector := v.CatalogSector
@@ -686,9 +682,13 @@ func (of OperatorFactory) Name() string {
 
 // SeemsToMatch returns true if the []byte disk image seems to match the
 // system of this operator.
-func (of OperatorFactory) SeemsToMatch(diskbytes []byte, debug bool) bool {
+func (of OperatorFactory) SeemsToMatch(rawbytes []byte, debug bool) bool {
 	// For now, just return true if we can run Catalog successfully.
-	_, _, err := ReadCatalog(diskbytes, debug)
+	swizzled, err := of.swizzle(rawbytes)
+	if err != nil {
+		return false
+	}
+	_, _, err = ReadCatalog(swizzled, debug)
 	if err != nil {
 		return false
 	}
@@ -696,6 +696,14 @@ func (of OperatorFactory) SeemsToMatch(diskbytes []byte, debug bool) bool {
 }
 
 // Operator returns an Operator for the []byte disk image.
-func (of OperatorFactory) Operator(diskbytes []byte, debug bool) (types.Operator, error) {
-	return operator{data: diskbytes, debug: debug}, nil
+func (of OperatorFactory) Operator(rawbytes []byte, debug bool) (types.Operator, error) {
+	swizzled, err := of.swizzle(rawbytes)
+	if err != nil {
+		return nil, err
+	}
+	return operator{data: swizzled, debug: debug}, nil
+}
+
+func (of OperatorFactory) swizzle(rawbytes []byte) ([]byte, error) {
+	return disk.Swizzle(rawbytes, disk.Dos33PhysicalToLogicalSectorMap)
 }
diff --git a/helpers/helpers.go b/helpers/helpers.go
index 1b85fe0..eed3847 100644
--- a/helpers/helpers.go
+++ b/helpers/helpers.go
@@ -5,7 +5,10 @@
 package helpers
 
 import (
-	"io/ioutil"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
 	"os"
 )
 
@@ -13,7 +16,23 @@ import (
 // is "-", in which case it reads from stdin.
 func FileContentsOrStdIn(s string) ([]byte, error) {
 	if s == "-" {
-		return ioutil.ReadAll(os.Stdin)
+		return io.ReadAll(os.Stdin)
 	}
-	return ioutil.ReadFile(s)
+	return os.ReadFile(s)
+}
+
+func WriteOutput(outfilename string, contents []byte, infilename string, force bool) error {
+	if outfilename == "" {
+		outfilename = infilename
+	}
+	if outfilename == "-" {
+		_, err := os.Stdout.Write(contents)
+		return err
+	}
+	if !force {
+		if _, err := os.Stat(outfilename); !errors.Is(err, fs.ErrNotExist) {
+			return fmt.Errorf("cannot overwrite file %q without --force (-f)", outfilename)
+		}
+	}
+	return os.WriteFile(outfilename, contents, 0666)
 }
diff --git a/main.go b/main.go
index 2ca0d72..41741db 100644
--- a/main.go
+++ b/main.go
@@ -5,6 +5,8 @@ package main
 import (
 	"github.com/zellyn/diskii/cmd"
 	"github.com/zellyn/diskii/dos3"
+	"github.com/zellyn/diskii/prodos"
+	"github.com/zellyn/diskii/supermon"
 	"github.com/zellyn/diskii/types"
 
 	"fmt"
@@ -14,11 +16,10 @@ import (
 )
 
 var cli struct {
-	Debug  bool   `kong:"short='v',help='Enable debug mode.'"`
-	Order  string `kong:"default='auto',enum='auto,raw,do,po',help='Logical-to-physical sector order.'"`
-	System string `kong:"default='auto',enum='auto,dos3',help='DOS system used for image.'"`
+	Debug bool `kong:"short='v',help='Enable debug mode.'"`
 
-	Ls cmd.LsCmd `cmd:"" aliases:"cat,catalog" help:"List paths."`
+	Ls      cmd.LsCmd      `cmd:"" aliases:"cat,catalog" help:"List paths."`
+	Reorder cmd.ReorderCmd `cmd:"" help:"Reorder disk images."`
 }
 
 func run() error {
@@ -34,13 +35,11 @@ func run() error {
 	)
 
 	globals := &types.Globals{
-		Debug:  cli.Debug,
-		Order:  cli.Order,
-		System: cli.System,
+		Debug: cli.Debug,
 		DiskOperatorFactories: []types.OperatorFactory{
 			dos3.OperatorFactory{},
-			// supermon.OperatorFactory,
-			// prodos.DiskOperatorFactory,
+			supermon.OperatorFactory{},
+			prodos.OperatorFactory{},
 		},
 	}
 	// Call the Run() method of the selected parsed command.
diff --git a/notes.org b/notes.org
index 12bb8d5..6343ecb 100644
--- a/notes.org
+++ b/notes.org
@@ -85,3 +85,8 @@ F8        CLD
 
 echo -n -e '\x20\x40\x03\x6D\x01\xDC\x2C\x02\xDF\x2C\x00\x60\xF8\x4C\x00\x60' | diskii put -f ./lib/supermon/testdata/chacha20.dsk DF01:FHELLO -
 echo -n -e '\x20\x58\xFC\xA2\x00\xBD\x13\x60\xF0\x06\x20\xED\xFD\xE8\xD0\xF5\x4C\x10\x60\xC8\xC5\xCC\xCC\xCF\xAC\xA0\xD7\xCF\xD2\xCC\xC4\x00' | diskii put -f ./lib/supermon/testdata/chacha20.dsk DF02:FWORLD -
+
+* Sources
+
+** ProDOS
+[[https://www.apple.asimov.net/documentation/source_code/Apple%20ProDOS%20Boot%20Source.pdf][ProDOS boot source]]
diff --git a/prodos/prodos.go b/prodos/prodos.go
index a893fcf..7671c26 100644
--- a/prodos/prodos.go
+++ b/prodos/prodos.go
@@ -7,9 +7,9 @@ package prodos
 import (
 	"encoding/binary"
 	"fmt"
-	"io"
 
 	"github.com/zellyn/diskii/disk"
+	"github.com/zellyn/diskii/types"
 )
 
 // Storage types.
@@ -104,11 +104,11 @@ func (vbm VolumeBitMap) IsFree(block uint16) bool {
 
 // readVolumeBitMap reads the entire volume bitmap from a block
 // device.
-func readVolumeBitMap(bd disk.BlockDevice, startBlock uint16) (VolumeBitMap, error) {
-	blocks := bd.Blocks() / 4096
+func readVolumeBitMap(devicebytes []byte, startBlock uint16) (VolumeBitMap, error) {
+	blocks := uint16(len(devicebytes) / 512 / 4096)
 	vbm := NewVolumeBitMap(startBlock, blocks)
 	for i := 0; i < len(vbm); i++ {
-		if err := disk.UnmarshalBlock(bd, &vbm[i], vbm[i].GetBlock()); err != nil {
+		if err := disk.UnmarshalBlock(devicebytes, &vbm[i], vbm[i].GetBlock()); err != nil {
 			return nil, fmt.Errorf("cannot read block %d (device block %d) of Volume Bit Map: %v", i, vbm[i].GetBlock(), err)
 		}
 	}
@@ -116,9 +116,9 @@ func readVolumeBitMap(bd disk.BlockDevice, startBlock uint16) (VolumeBitMap, err
 }
 
 // Write writes the Volume Bit Map to a block device.
-func (vbm VolumeBitMap) Write(bd disk.BlockDevice) error {
+func (vbm VolumeBitMap) Write(devicebytes []byte) error {
 	for i, bp := range vbm {
-		if err := disk.MarshalBlock(bd, bp); err != nil {
+		if err := disk.MarshalBlock(devicebytes, bp); err != nil {
 			return fmt.Errorf("cannot write block %d (device block %d) of Volume Bit Map: %v", i, bp.GetBlock(), err)
 		}
 	}
@@ -351,14 +351,14 @@ type FileDescriptor struct {
 	HeaderPointer uint16 // Block  number of the key block for the directory which describes this file.
 }
 
-// descriptor returns a disk.Descriptor for a FileDescriptor.
-func (fd FileDescriptor) descriptor() disk.Descriptor {
-	desc := disk.Descriptor{
+// descriptor returns a types.Descriptor for a FileDescriptor.
+func (fd FileDescriptor) descriptor() types.Descriptor {
+	desc := types.Descriptor{
 		Name:   fd.Name(),
 		Blocks: int(fd.BlocksUsed),
 		Length: int(fd.Eof[0]) + int(fd.Eof[1])<<8 + int(fd.Eof[2])<<16,
-		Locked: false, // TODO(zellyn): use prodos-style access in disk.Descriptor
-		Type:   disk.Filetype(fd.FileType),
+		Locked: false, // TODO(zellyn): use prodos-style access in types.Descriptor
+		Type:   types.Filetype(fd.FileType),
 	}
 	return desc
 }
@@ -652,18 +652,18 @@ func (v Volume) subdirDescriptors() []FileDescriptor {
 
 // readVolume reads the entire volume and subdirectories from a device
 // into memory.
-func readVolume(bd disk.BlockDevice, keyBlock uint16) (Volume, error) {
+func readVolume(devicebytes []byte, keyBlock uint16) (Volume, error) {
 	v := Volume{
 		keyBlock:       &VolumeDirectoryKeyBlock{},
 		subdirsByBlock: make(map[uint16]*Subdirectory),
 		subdirsByName:  make(map[string]*Subdirectory),
 	}
 
-	if err := disk.UnmarshalBlock(bd, v.keyBlock, keyBlock); err != nil {
+	if err := disk.UnmarshalBlock(devicebytes, v.keyBlock, keyBlock); err != nil {
 		return v, fmt.Errorf("cannot read first block of volume directory (block %d): %v", keyBlock, err)
 	}
 
-	if vbm, err := readVolumeBitMap(bd, v.keyBlock.Header.BitMapPointer); err != nil {
+	if vbm, err := readVolumeBitMap(devicebytes, v.keyBlock.Header.BitMapPointer); err != nil {
 		return v, err
 	} else {
 		v.bitmap = &vbm
@@ -671,7 +671,7 @@ func readVolume(bd disk.BlockDevice, keyBlock uint16) (Volume, error) {
 
 	for block := v.keyBlock.Next; block != 0; block = v.blocks[len(v.blocks)-1].Next {
 		vdb := VolumeDirectoryBlock{}
-		if err := disk.UnmarshalBlock(bd, &vdb, block); err != nil {
+		if err := disk.UnmarshalBlock(devicebytes, &vdb, block); err != nil {
 			return v, err
 		}
 		v.blocks = append(v.blocks, &vdb)
@@ -681,7 +681,7 @@ func readVolume(bd disk.BlockDevice, keyBlock uint16) (Volume, error) {
 
 	for i := 0; i < len(sdds); i++ {
 		sdd := sdds[i]
-		sub, err := readSubdirectory(bd, sdd)
+		sub, err := readSubdirectory(devicebytes, sdd)
 		if err != nil {
 			return v, err
 		}
@@ -751,18 +751,18 @@ func parentDirName(parentDirectoryBlock uint16, keyBlock uint16, subdirMap map[u
 
 // readSubdirectory reads a single subdirectory from a device into
 // memory.
-func readSubdirectory(bd disk.BlockDevice, fd FileDescriptor) (Subdirectory, error) {
+func readSubdirectory(devicebytes []byte, fd FileDescriptor) (Subdirectory, error) {
 	s := Subdirectory{
 		keyBlock: &SubdirectoryKeyBlock{},
 	}
 
-	if err := disk.UnmarshalBlock(bd, s.keyBlock, fd.KeyPointer); err != nil {
+	if err := disk.UnmarshalBlock(devicebytes, s.keyBlock, fd.KeyPointer); err != nil {
 		return s, fmt.Errorf("cannot read first block of subdirectory %q (block %d): %v", fd.Name(), fd.KeyPointer, err)
 	}
 
 	for block := s.keyBlock.Next; block != 0; block = s.blocks[len(s.blocks)-1].Next {
 		sdb := SubdirectoryBlock{}
-		if err := disk.UnmarshalBlock(bd, &sdb, block); err != nil {
+		if err := disk.UnmarshalBlock(devicebytes, &sdb, block); err != nil {
 			return s, err
 		}
 		s.blocks = append(s.blocks, &sdb)
@@ -783,10 +783,11 @@ func copyBytes(dst, src []byte) int {
 // operator is a disk.Operator - an interface for performing
 // high-level operations on files and directories.
 type operator struct {
-	dev disk.BlockDevice
+	data  []byte
+	debug bool
 }
 
-var _ disk.Operator = operator{}
+var _ types.Operator = operator{}
 
 // operatorName is the keyword name for the operator that undestands
 // prodos disks/devices.
@@ -797,11 +798,6 @@ func (o operator) Name() string {
 	return operatorName
 }
 
-// Order returns the sector or block order of the underlying storage.
-func (o operator) Order() string {
-	return o.dev.Order()
-}
-
 // HasSubdirs returns true if the underlying operating system on the
 // disk allows subdirectories.
 func (o operator) HasSubdirs() bool {
@@ -810,14 +806,14 @@ func (o operator) HasSubdirs() bool {
 
 // Catalog returns a catalog of disk entries. subdir should be empty
 // for operating systems that do not support subdirectories.
-func (o operator) Catalog(subdir string) ([]disk.Descriptor, error) {
+func (o operator) Catalog(subdir string) ([]types.Descriptor, error) {
 
-	vol, err := readVolume(o.dev, 2)
+	vol, err := readVolume(o.data, 2)
 	if err != nil {
 		return nil, err
 	}
 
-	var result []disk.Descriptor
+	var result []types.Descriptor
 
 	if subdir == "" {
 		for _, desc := range vol.descriptors() {
@@ -842,8 +838,8 @@ func (o operator) Catalog(subdir string) ([]disk.Descriptor, error) {
 }
 
 // GetFile retrieves a file by name.
-func (o operator) GetFile(filename string) (disk.FileInfo, error) {
-	return disk.FileInfo{}, fmt.Errorf("%s doesn't implement GetFile yet", operatorName)
+func (o operator) GetFile(filename string) (types.FileInfo, error) {
+	return types.FileInfo{}, fmt.Errorf("%s doesn't implement GetFile yet", operatorName)
 }
 
 // Delete deletes a file by name. It returns true if the file was
@@ -855,37 +851,49 @@ func (o operator) Delete(filename string) (bool, error) {
 // PutFile writes a file by name. If the file exists and overwrite
 // is false, it returns with an error. Otherwise it returns true if
 // an existing file was overwritten.
-func (o operator) PutFile(fileInfo disk.FileInfo, overwrite bool) (existed bool, err error) {
+func (o operator) PutFile(fileInfo types.FileInfo, overwrite bool) (existed bool, err error) {
 	return false, fmt.Errorf("%s doesn't implement PutFile yet", operatorName)
 }
 
-// Write writes the underlying device blocks to the given writer.
-func (o operator) Write(w io.Writer) (int, error) {
-	return o.dev.Write(w)
+// OperatorFactory is a types.OperatorFactory for ProDos disks.
+type OperatorFactory struct {
 }
 
-// deviceOperatorFactory is the factory that returns prodos operators
-// given device images.
-func deviceOperatorFactory(bd disk.BlockDevice) (disk.Operator, error) {
-	op := operator{dev: bd}
-	_, err := op.Catalog("")
-	if err != nil {
-		return nil, fmt.Errorf("Cannot read catalog. Underlying error: %v", err)
+// Name returns the name of the operator.
+func (of OperatorFactory) Name() string {
+	return operatorName
+}
+
+// SeemsToMatch returns true if the []byte disk image seems to match the
+// system of this operator.
+func (of OperatorFactory) SeemsToMatch(devicebytes []byte, debug bool) bool {
+	// For now, just return true if we can run Catalog successfully.
+	if len(devicebytes) == disk.FloppyDiskBytes {
+		swizzled, err := of.swizzle(devicebytes)
+		if err != nil {
+			return false
+		}
+		devicebytes = swizzled
 	}
-	return op, nil
-}
-
-// DiskOperatorFactory is the factory that returns dos3 operators
-// given disk images.
-func DiskOperatorFactory(sd disk.SectorDisk) (disk.Operator, error) {
-	bd, err := disk.BlockDeviceFromSectorDisk(sd)
+	_, err := readVolume(devicebytes, 2)
 	if err != nil {
-		return nil, err
+		return false
 	}
-	return deviceOperatorFactory(bd)
+	return true
 }
 
-func init() {
-	disk.RegisterDeviceOperatorFactory(operatorName, deviceOperatorFactory)
-	disk.RegisterDiskOperatorFactory(operatorName, DiskOperatorFactory)
+// Operator returns an Operator for the []byte disk image.
+func (of OperatorFactory) Operator(devicebytes []byte, debug bool) (types.Operator, error) {
+	if len(devicebytes) == disk.FloppyDiskBytes {
+		swizzled, err := of.swizzle(devicebytes)
+		if err != nil {
+			return nil, err
+		}
+		devicebytes = swizzled
+	}
+	return operator{data: devicebytes, debug: debug}, nil
+}
+
+func (of OperatorFactory) swizzle(rawbytes []byte) ([]byte, error) {
+	return disk.Swizzle(rawbytes, disk.ProDosPhysicalToLogicalSectorMap)
 }
diff --git a/supermon/supermon.go b/supermon/supermon.go
index dcd1e47..a62028b 100644
--- a/supermon/supermon.go
+++ b/supermon/supermon.go
@@ -12,6 +12,7 @@ import (
 
 	"github.com/zellyn/diskii/disk"
 	"github.com/zellyn/diskii/errors"
+	"github.com/zellyn/diskii/types"
 )
 
 const (
@@ -253,14 +254,14 @@ func decodeSymbol(five []byte, extra byte) string {
 	value := uint64(five[0]) + uint64(five[1])<<8 + uint64(five[2])<<16 + uint64(five[3])<<24 + uint64(five[4])<<32 + uint64(extra)<<40
 	for value&0x1f > 0 {
 		if value&0x1f < 27 {
-			result = result + string(value&0x1f+'@')
+			result = result + string(rune(value&0x1f+'@'))
 			value >>= 5
 			continue
 		}
 		if value&0x20 == 0 {
-			result = result + string((value&0x1f)-0x1b+'0')
+			result = result + string(rune((value&0x1f)-0x1b+'0'))
 		} else {
-			result = result + string((value&0x1f)-0x1b+'5')
+			result = result + string(rune((value&0x1f)-0x1b+'5'))
 		}
 		value >>= 6
 	}
@@ -639,74 +640,75 @@ func (st SymbolTable) FilesForCompoundName(filename string) (numFile byte, named
 	return numFile, namedFile, parts[1], nil
 }
 
-// Operator is a disk.Operator - an interface for performing
+// operator is a disk.Operator - an interface for performing
 // high-level operations on files and directories.
-type Operator struct {
-	data []byte
-	SM   SectorMap
-	ST   SymbolTable
+type operator struct {
+	data  []byte
+	SM    SectorMap
+	ST    SymbolTable
+	debug bool
 }
 
-var _ disk.Operator = Operator{}
+var _ types.Operator = operator{}
 
 // operatorName is the keyword name for the operator that undestands
 // NakedOS/Super-Mon disks.
 const operatorName = "nakedos"
 
 // Name returns the name of the Operator.
-func (o Operator) Name() string {
+func (o operator) Name() string {
 	return operatorName
 }
 
 // HasSubdirs returns true if the underlying operating system on the
 // disk allows subdirectories.
-func (o Operator) HasSubdirs() bool {
+func (o operator) HasSubdirs() bool {
 	return false
 }
 
 // Catalog returns a catalog of disk entries. subdir should be empty
 // for operating systems that do not support subdirectories.
-func (o Operator) Catalog(subdir string) ([]disk.Descriptor, error) {
-	var descs []disk.Descriptor
+func (o operator) Catalog(subdir string) ([]types.Descriptor, error) {
+	var descs []types.Descriptor
 	sectorsByFile := o.SM.SectorsByFile()
 	for file := byte(1); file < FileReserved; file++ {
 		l := len(sectorsByFile[file])
 		if l == 0 {
 			continue
 		}
-		descs = append(descs, disk.Descriptor{
+		descs = append(descs, types.Descriptor{
 			Name:     NameForFile(file, o.ST),
 			Fullname: FullnameForFile(file, o.ST),
 			Sectors:  l,
 			Length:   l * 256,
 			Locked:   false,
-			Type:     disk.FiletypeBinary,
+			Type:     types.FiletypeBinary,
 		})
 	}
 	return descs, nil
 }
 
 // GetFile retrieves a file by name.
-func (o Operator) GetFile(filename string) (disk.FileInfo, error) {
+func (o operator) GetFile(filename string) (types.FileInfo, error) {
 	file, err := o.ST.FileForName(filename)
 	if err != nil {
-		return disk.FileInfo{}, err
+		return types.FileInfo{}, err
 	}
 	data, err := o.SM.ReadFile(o.data, file)
 	if err != nil {
-		return disk.FileInfo{}, fmt.Errorf("error reading file DF%02x: %v", file, err)
+		return types.FileInfo{}, fmt.Errorf("error reading file DF%02x: %v", file, err)
 	}
 	if len(data) == 0 {
-		return disk.FileInfo{}, fmt.Errorf("file DF%02x not fount", file)
+		return types.FileInfo{}, fmt.Errorf("file DF%02x not fount", file)
 	}
-	desc := disk.Descriptor{
+	desc := types.Descriptor{
 		Name:    NameForFile(file, o.ST),
 		Sectors: len(data) / 256,
 		Length:  len(data),
 		Locked:  false,
-		Type:    disk.FiletypeBinary,
+		Type:    types.FiletypeBinary,
 	}
-	fi := disk.FileInfo{
+	fi := types.FileInfo{
 		Descriptor: desc,
 		Data:       data,
 	}
@@ -718,7 +720,7 @@ func (o Operator) GetFile(filename string) (disk.FileInfo, error) {
 
 // Delete deletes a file by name. It returns true if the file was
 // deleted, false if it didn't exist.
-func (o Operator) Delete(filename string) (bool, error) {
+func (o operator) Delete(filename string) (bool, error) {
 	file, err := o.ST.FileForName(filename)
 	if err != nil {
 		return false, err
@@ -742,8 +744,8 @@ func (o Operator) Delete(filename string) (bool, error) {
 // PutFile writes a file by name. If the file exists and overwrite
 // is false, it returns with an error. Otherwise it returns true if
 // an existing file was overwritten.
-func (o Operator) PutFile(fileInfo disk.FileInfo, overwrite bool) (existed bool, err error) {
-	if fileInfo.Descriptor.Type != disk.FiletypeBinary {
+func (o operator) PutFile(fileInfo types.FileInfo, overwrite bool) (existed bool, err error) {
+	if fileInfo.Descriptor.Type != types.FiletypeBinary {
 		return false, fmt.Errorf("%s: only binary file type supported", operatorName)
 	}
 	if fileInfo.Descriptor.Length != len(fileInfo.Data) {
@@ -783,9 +785,9 @@ func (o Operator) PutFile(fileInfo disk.FileInfo, overwrite bool) (existed bool,
 	return existed, nil
 }
 
-// OperatorFactory is the factory that returns supermon operators
+// XOperatorFactory is the factory that returns supermon operators
 // given disk images.
-func OperatorFactory(diskbytes []byte) (disk.Operator, error) {
+func XOperatorFactory(diskbytes []byte) (types.Operator, error) {
 	sm, err := LoadSectorMap(diskbytes)
 	if err != nil {
 		return nil, err
@@ -794,7 +796,50 @@ func OperatorFactory(diskbytes []byte) (disk.Operator, error) {
 		return nil, err
 	}
 
-	op := Operator{data: diskbytes, SM: sm}
+	op := operator{data: diskbytes, SM: sm}
+
+	st, err := sm.ReadSymbolTable(diskbytes)
+	if err == nil {
+		op.ST = st
+	}
+
+	return op, nil
+}
+
+// OperatorFactory is a types.OperatorFactory for DOS 3.3 disks.
+type OperatorFactory struct {
+}
+
+// Name returns the name of the operator.
+func (of OperatorFactory) Name() string {
+	return operatorName
+}
+
+// SeemsToMatch returns true if the []byte disk image seems to match the
+// system of this operator.
+func (of OperatorFactory) SeemsToMatch(diskbytes []byte, debug bool) bool {
+	// For now, just return true if we can run Catalog successfully.
+	sm, err := LoadSectorMap(diskbytes)
+	if err != nil {
+		return false
+	}
+	if err := sm.Verify(); err != nil {
+		return false
+	}
+	return true
+}
+
+// Operator returns an Operator for the []byte disk image.
+func (of OperatorFactory) Operator(diskbytes []byte, debug bool) (types.Operator, error) {
+	sm, err := LoadSectorMap(diskbytes)
+	if err != nil {
+		return nil, err
+	}
+	if err := sm.Verify(); err != nil {
+		return nil, err
+	}
+
+	op := operator{data: diskbytes, SM: sm, debug: debug}
 
 	st, err := sm.ReadSymbolTable(diskbytes)
 	if err == nil {
diff --git a/supermon/supermon_test.go b/supermon/supermon_test.go
index e0c495a..eaeec0c 100644
--- a/supermon/supermon_test.go
+++ b/supermon/supermon_test.go
@@ -3,12 +3,14 @@
 package supermon
 
 import (
+	"os"
 	"reflect"
 	"strings"
 	"testing"
 
 	"github.com/kr/pretty"
 	"github.com/zellyn/diskii/disk"
+	"github.com/zellyn/diskii/types"
 )
 
 const testDisk = "testdata/chacha20.dsk"
@@ -27,16 +29,36 @@ No more; and by a sleep, to say we end
 
 // loadSectorMap loads a sector map for the disk image contained in
 // filename. It returns the sector map and a sector disk.
-func loadSectorMap(filename string) (SectorMap, disk.SectorDisk, error) {
-	sd, err := disk.LoadDSK(filename)
+func loadSectorMap(filename string) (SectorMap, []byte, error) {
+	rawbytes, err := os.ReadFile(filename)
 	if err != nil {
 		return nil, nil, err
 	}
-	sm, err := LoadSectorMap(sd)
+	diskbytes, err := disk.Swizzle(rawbytes, disk.Dos33LogicalToPhysicalSectorMap)
 	if err != nil {
 		return nil, nil, err
 	}
-	return sm, sd, nil
+	sm, err := LoadSectorMap(diskbytes)
+	if err != nil {
+		return nil, nil, err
+	}
+	return sm, diskbytes, nil
+}
+
+// getOperator gets a types.Operator for the given NakedOS disk, assumed to be
+// in "do" order.
+func getOperator(filename string) (types.Operator, error) {
+	f, err := os.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	op, _, err := disk.OpenImage(f, "do", "nakedos", &types.Globals{
+		DiskOperatorFactories: []types.OperatorFactory{OperatorFactory{}},
+	})
+	if err != nil {
+		return nil, err
+	}
+	return op, nil
 }
 
 // TestReadSectorMap tests the reading of the sector map of a test
@@ -126,11 +148,7 @@ func TestReadSymbolTable(t *testing.T) {
 // TestGetFile tests the retrieval of a file's contents, using the
 // Operator interface.
 func TestGetFile(t *testing.T) {
-	sd, err := disk.OpenDisk(testDisk)
-	if err != nil {
-		t.Fatal(err)
-	}
-	op, err := disk.OperatorForDisk(sd)
+	op, err := getOperator(testDisk)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -213,20 +231,16 @@ func TestReadWriteSymbolTable(t *testing.T) {
 // TestPutFile tests the creation of a file, using the Operator
 // interface.
 func TestPutFile(t *testing.T) {
-	sd, err := disk.OpenDisk(testDisk)
-	if err != nil {
-		t.Fatal(err)
-	}
-	op, err := disk.OperatorForDisk(sd)
+	op, err := getOperator(testDisk)
 	if err != nil {
 		t.Fatal(err)
 	}
 	contents := []byte(cities)
-	fileInfo := disk.FileInfo{
-		Descriptor: disk.Descriptor{
+	fileInfo := types.FileInfo{
+		Descriptor: types.Descriptor{
 			Name:   "FNEWFILE",
 			Length: len(contents),
-			Type:   disk.FiletypeBinary,
+			Type:   types.FiletypeBinary,
 		},
 		Data: contents,
 	}
diff --git a/types/types.go b/types/types.go
index eccc3e2..ddf1a8f 100644
--- a/types/types.go
+++ b/types/types.go
@@ -2,9 +2,7 @@ package types
 
 // Globals holds flags and configuration that are shared globally.
 type Globals struct {
-	Debug  bool
-	Order  string //Logical-to-physical sector order
-	System string // DOS system used for image
+	Debug bool
 
 	DiskOperatorFactories []OperatorFactory
 }
diff --git a/woz/woz_test.go b/woz/woz_test.go
index 082a12d..6e717d1 100644
--- a/woz/woz_test.go
+++ b/woz/woz_test.go
@@ -9,8 +9,7 @@ import (
 )
 
 func TestBasicLoad(t *testing.T) {
-	bb := data.MustAsset("data/disks/dos33master.woz")
-	wz, err := woz.Decode(bytes.NewReader(bb))
+	wz, err := woz.Decode(bytes.NewReader(data.DOS33master_woz))
 	if err != nil {
 		t.Fatal(err)
 	}