Many long-time iPod users have become accustomed to the ability to use their iPods as portable hard disks to store and transfer files between different computers. This still is easily accomplished on both iPod Click Wheel and shuffle models, since these iPods can appear as USB hard drives on your computer. All you need to do is enable Disk Mode in iTunes, and the iPod suddenly becomes both a media player and a file storage device. However, Apple did away with Disk Mode on the iPhone and iPod touch. The new synchronization protocol that these devices use does not require that they appear to the computer as an external storage device, and for whatever reason Apple has not yet specifically added this feature into these models. Fortunately, as with other features missing from the iPhone and iPod touch in their native configuration, enterprising third-party developers have stepped in to fill the void, albeit in somewhat different ways than you may expect.
Today we review six apps that provide file storage and transfer capabilities for the iPhone and iPod touch, allowing you to not only store and transport your files, but also to actually view them on the device itself if they are in a supported format. However, these tools don’t actually provide the old-style “Disk Mode” that the traditional iPod models do—rather than operating over USB and appearing as an external storage device, these applications all work over Wi-Fi using various network protocols. This is due to Apple SDK restrictions on both the iPhone’s Bluetooth and the iPod touch/iPhone Dock Connector, neither of which can be accessed by developers for these purposes. Therefore, your iPhone or iPod touch and your computer will need to be on the same Wi-Fi network if you want to transfer files to and from your device.
FileMagnet
FileMagnet ($5) from Magnetism Studios was the first App Store file storage app release, as it was actually available at the App Store’s launch. It lets you transfer files to and from your iPhone or iPod touch using the company’s own file transfer application for Mac OS X, downloaded free from the Magnetism Studios web site link on FileMagnet’s App Store page. Unfortunately, as of this writing there is no Windows version of the uploader app available, meaning this application will presently be of little use for Windows users.
Downloading and using the app is very straightforward; it requires no special network configuration knowledge or customization. Loading the app provides a simple transfer window that displays the content of your connected device, as well as any content that has been queued up for transfer to the device.
The FileMagnet app finds the iPhone or iPod touch automatically as long as they are on the same Wi-Fi network, a process that we’ve tested on a couple of machines without any sort of issue. As an added security measure, FileMagnet will prompt you to authorize your connection the first time you use the FileMagnet app on a new computer.
Adding content is as simple as dragging it from your Finder window into the FileMagnet desktop application. If the iPhone or iPod touch is connected, files will begin transferring immediately; otherwise they are automatically queued up and transferred the next time your device is connected.
Any files in the pending file queue will remain there awaiting transfer until they are either successfully transferred or manually removed. Files transferred to your iPhone or iPod touch will appear directly within the FileMagnet app as soon as you click on it.
Files can also be transferred back from the device via the FileMagnet desktop application, or deleted directly on the device in the usual manner: swipe left-to-right across the file entry, or tap the EDIT button and tap the delete symbol beside each entry. Note that there is no way to create folders directly on the device to organize your files, however transferring an entire folder from your computer will create a sub-folder entry on your device for those files. You cannot move existing files between sub-folders.
You can transfer any file or folder to your device via the FileMagnet desktop app, but as an added bonus, FileMagnet also provides support for viewing popular file formats. Specifically, FileMagnet will allow on-device viewing of JPG, PDF, HTML, text, Microsoft Office Word, Excel, and Powerpoint documents, Apple iWork Pages, Numbers, and Keynote documents, and any video or audio file that could otherwise be synced to the device from iTunes. Files that can be viewed on the device will have a small arrow to the right of the file listing. Tapping on the file entry will open a viewer window.
During viewing, the usual zooming and panning features are available, while rotating the device will also reorient the viewer to landscape mode, although oddly only the content is rotated—the interface itself remains in portrait mode.
In addition, FileMagnet is the only application we’ve reviewed that will remember your place if you exit it while viewing a document and automatically return to it when you re-launch the application. All of the other applications return to the application’s main screen when re-launched.
FileMagnet is a very useful no-frills solution for those who simply want to carry a few files around with them on their device and do not mind using a companion desktop application for file transfer. This application also offers the best range of file format viewing support that we have observed, specifically in the area of iWork formats, and seems to have no issues with larger files. We were able to open and display our Free iPod + iPhone Book 4 in about 10 seconds; some minor lagging was observed on this particularly large file when rotating the device (changing orientation) and scrolling through the document, but this was not unexpected, and the same delays were observed when opening the same file from the iPhone Safari browser or Mail application. It should go without saying, however, that this is considered a more extreme example of file support, and that the typical user’s much smaller documents will not exhibit these problems. Most average documents we loaded responded very quickly to loading, panning, zooming and scrolling gestures.
While the use of a secondary computer-to-iPhone/iPod transferring program may limit the usability of FileMagnet across multiple computers, the app itself is a simple and quick download that requires no actual installation on the computer, and has the significant advantage of automatically establishing the connection between the FileMagnet app on the device and the computer with no user configuration or intervention required. Further, the use of a dedicated transfer app can offer a small security benefit over other solutions that simply expose your device’s content via standard network protocols such as HTTP.
In summary, FileMagnet is a good solution for those Mac users who simply want to carry around a few documents on their device, don’t want to deal with configuration issues and aren’t too concerned about maximum portability between computers. At $5, it’s reasonably priced, too. iLounge Rating: A-.
Files
Olive Toast’s Files ($7) was the second offering to appear on the App Store, and takes a slightly different direction from FileMagnet. Rather than using a desktop application of its own, Files presents your device as a server using the WebDAV protocol. This allows you to connect to your device from Finder or Windows Explorer directly without requiring any other applications to be installed on your computer. When you first start Files, you are presented with a brief configuration screen where you must set a username and password which will be used to log on to your device from the desktop.
You may enter any values you like here—these do not correspond to any userids and passwords used anywhere else, they are simply what you will enter when connecting to the device itself. Note that you may also enable “Guest” access to allow access to the “Public” folder without a username and password. When Guest access is enabled, users on your local Wi-Fi network will be able to connect to your Public folder with read/write access. Note that you may also set a Disk Quota on this screen. This limits the maximum amount of space that can be used by Files to store your data—the WebDAV share will simply appear as a file system of this particular size. This is useful for preventing your files from inadvertently taking up all of the remaining available space on your device.
Once you have specified these options and tapped the “Done” button, the main Files screen appears, providing the IP address of your iPhone or iPod touch that can be used to connect from your computer.
Connecting to Files is done in the same way as you would for any WebDAV server. In Mac OS X Finder, simply choose Go, Connect to Server and enter the URL shown by Files on your device.
When prompted, enter your user name and password, as specified on the Files setup screen.
Your device should then appear as a shared network resource in your Finder window.
For Windows users, the process is somewhat similar in concept, although slightly easier. You can simply enter the HTTP WebDAV URL provided by Files into your Windows Explorer or Internet Explorer address bar, and Windows will handle the rest of the connection details for you, again presenting your device as a shared folder. To access your public folder in Guest mode (if it is enabled), simply append the word “Public” to the end of the URL (eg, “http://192.168.100.191:8080/Public”). Once you have connected to your device, you would transfer and manage files in the same way you would with any other network share, using the normal tools in Finder or Windows Explorer.
Displaying your files on the device itself is relatively straightforward. The main Files window shows a listing of your top-level folder content, and any sub-folders that have been created through Windows Explorer or Finder are also displayed.
You can delete files directly from the device interface in the usual swipe-and-tap manner, but you cannot move files between folders or create new folders directly on the device—for this you will have to return to your Finder or Windows Explorer interface.
One additional feature that Files does offer is the ability to filter a large file listing. The small magnifying glass icon in the bottom-right corner will open a search field which can be used to search on the file names within the current folder. Note that this only searches on file names and not on any of the content in the files themselves.
As with FileMagnet, Files provides support for storing any type of file, and for viewing several file formats, although its format list is slightly more nuanced than FileMagnet’; specifically, iWork files need a little assistance working on the device. The developer’s notes on the App Store page suggests that you can ZIP an iWork document before transfer, but we initially could not get this to work in our testing—the format still showed as unsupported. Eventually, we found that using “filename.pages.ZIP” was the format Files would read. Other common formats such as JPG, PDF, HTML, text, and Microsoft Office documents are supported, as well as any video or audio file that could be synced to the device from iTunes.
As with FileMagnet, turning your device sideways will provide viewing in landscape mode, although like FileMagnet, this also only rotates the content and not the actual interface. One stand-out feature of Files’ viewing capabilities is its bookmarking feature. When viewing any file, you can add a bookmark to it at any position simply by tapping the small plus sign which appears in the bottom left corner of the file viewing window.
You can name these bookmarks, and then later return to them by tapping the Bookmarks button in the file viewer. These bookmarks remain in place as long as the file is on your device, however they are lost if you remove the file from your device, even if you copy it off to your computer and back on. Files also offers the unique ability to transfer pictures that you have stored on the device via Files over to your actual Saved Photos or Camera Roll, although the prompt for this is oddly labelled as “Add to iPhoto.”
In our testing, Files appeared to be slightly slower in rendering and displaying larger PDF files, although once loaded, scrolling and reorienting into landscape mode both appeared to be smoother than with other applications. This suggests that Files is simply taking additional time to pre-load the file into memory to provide a slightly smoother viewing experience for the user. The largest file we tested, our 27 MB Free iPod + iPhone Book 4, took around 25 seconds to load, however attempts to load this file also resulted in the Files application crashing completely back to the Home screen about a third of the time. Note that this problem was not observed with smaller PDF files and standard Microsoft Office documents, so it appears to be simply an issue in dealing with larger files. Our 9.5 MB 2008 iPod + iPhone Buyer’s Guide loaded without any problems, for example, albeit more slowly than on the other applications we tested.
In summary, Files is a reasonable offering for the user who wants more seamless integration with Finder or Windows Explorer and doesn’t mind dealing with IP addresses and user names and passwords to do so; the easier WebDAV integration on Windows XP and Vista makes this a good option for PC owners. The interface is otherwise clean and simple, with the benefit of a nice bookmarking feature, and the only issues being its stability in dealing with large PDF files and its required assistance when dealing with iWork formats. However, for users who do not work with larger files or iWork formats, these issues will be of little concern. iLounge Rating: B+.
DataCase
Veiosoft LLC’s DataCase ($7) was the third entry in the App Store offerings, arriving shortly after Files. Much like Files, DataCase presents your iPhone or iPod touch to your computer as a network file server. However, unlike Files, DataCase uses the AFP, HTTP and FTP protocols, rather than WebDAV. In particular, its use of the AFP protocol combined with Bonjour advertising means that it will seamlessly appear in Mac OS X Finder as a network device without any additional effort required by the end user. In fact, starting DataCase requires no pre-configuration—you’re simply presented with the main DataCase screen.
This screen displays a listing of space occupied by each of the different document categories supported by DataCase and the amount of free space available. The large central ring also serves as a form of pie chart to graphically indicate how much space is taken up by your different file types as you fill the device. At the bottom of the screen, the IP address of your device is displayed for connecting via HTTP (from your web browser) or FTP (using an FTP client). For Mac users, however, the use of AFP makes the connection to your computer almost completely seamless. As long as your iPhone or iPod touch is connected to the same network as your computer, simply starting DataCase will cause it to show up as a network device in your Finder window.
Selecting your iPhone from the Finder window will present a list of “Volumes” present. By default, these include Drop Box and Shared Files, although you can configure additional virtual volumes (up to 16 in total) from DataCase itself. Rather than using a user name or password configuration, DataCase provides security by prompting you on the iPhone or iPod touch each time a new connection request is made to your device. Selecting one of the default volumes from Finder will pop-up a window in the DataCase application prompting you to accept or reject the incoming connection.
Accepting the connection will allow all files on that particular volume to be accessed via Finder. Note that requests for access are approved on a per-volume basis each time a new connection is established to DataCase. Once you are connected to DataCase from Finder, you can copy, move, rename, add and delete files as you normally would for any other network volume.
Windows users may find little benefit from the AFP support in DataCase, as most Windows workstations do not have AFP enabled by default. Instead, DataCase provides FTP access for Windows users, although the process is not quite as seamless as it is on Mac OS X. Windows users must manually connect to the FTP URL displayed in the DataCase application in much the same way as they do for the Files application. Once this FTP connection is established, however, files can be managed through Windows Explorer in the same way as they can for any other network volume.
To actually view your files in DataCase, you tap either on the specific category of files you would like to view (ie, “Documents” or “Photos”) or simply tap on the large folder icon in the center of the screen to browse all file types. The first browse screen will show each of your virtual volumes, and you can then drill down from there into each individual volume to view your files.
From the top-level volumes screen, you can also edit the properties of existing volumes and create new ones. DataCase supports up to 16 volumes and each volume can be configured with individual security settings, including whether it is even visible from your computer, whether DataCase prompts for connections to it, and the level of read/write access available when connected to it. In addition, an “iTunes Backup” flag allows you to determine whether the files contained on this volume are automatically backed up by iTunes as part of its normal iPhone and iPod touch backup process.
Browsing and viewing files on the device is handled in much the same way as it is for the other applications, though DataCase lacks support for Apple’s iWork format. Other common formats are supported, including JPG, PDF, HTML, text, and Microsoft Office documents, as well as any video or audio file format that could otherwise be transferred by iTunes.
You can delete files directly from the device interface in the usual swipe-and-tap manner, but you cannot move files between folders or create new folders directly on the device—for this you will have to return to your Finder or Windows Explorer interface. The Filter button in the bottom-right corner of the browse screen can be used to filter by file type, but unlike Files does not provide any additional searching capabilities.
To view a file, simply tap on it and DataCase will open a file viewer window in much the same way as FileMagnet and Files.
Turning the iPhone or iPod touch sideways will render the display in landscape mode, however unlike the other applications we’ve reviewed, DataCase reorients the entire user interface into landscape view.
In fact, DataCase can run entirely in landscape mode. As an additional nice touch, when in landscape mode the file sizes are also displayed beside each file.
In addition to reading and writing files via AFP or FTP, DataCase also provides support for reading/viewing your files through your browser using HTTP, simply by pointing your browser at the supplied HTTP URL shown on the main DataCase screen. A basic HTTP listing of your files and folders will be shown, and you can browse, view and download files directly from the device.
DataCase stores its additional settings under the iPhone or iPod touch Settings screen. From here you can turn each protocol on and off individually, set whether the file size is always shown—as opposed to only being shown in landscape mode—and choose a color scheme. Additionally, you can also set DataCase to prevent your iPhone or iPod touch from going to sleep when it’s running, a useful feature since your device will disconnect from your computer when it enters sleep mode.
In our testing, DataCase rendered files at about the same speed as FileMagnet, and had no problem loading and rendering our 27 MB Free iPod + iPhone Book 4 test file in about 10 seconds. Like FileMagnet, some minor lagging was notable with this large file when rotating and scrolling, but this again was reasonable considering the size of the file and the amount of graphical content contained inside. Typical Office document files and average-sized PDF files loaded and rendered without any noticeable delays.
In summary, DataCase is a very simple and straightforward app for transferring and viewing your files, particularly for Mac users with its AFP and Bonjour support providing seamless integration with the Mac OS X Finder; it rates an A- for those using Mac computers. Windows users may want to take a look as well for some of its more advanced volume management features, but won’t find it quite as seamless, the reason it rates slightly lower on this platform. The lack of support for iWork documents is the only other significant limitation to DataCase, which will hopefully be addressed in a future update. iLounge Rating: A-/B+.
MobileFinder
One of the more recent file storage entries in the App Store is actually an application first made popular as an unofficial offering for jailbroken iPhones several months ago. As the name MobileFinder
($2) implies, Pixio’s program attempts to do a bit more than just being a file transfer and storage app, instead providing more enhanced file management capabilities directly on your device.
In this sense, MobileFinder is more of a file management application for your iPhone or iPod touch than merely a file storage and viewing application. However, serious problems with this application led us to issue a very low rating and a warning; Apple should never have allowed something with MobileFinder’s bugs to appear for sale in the App Store.
MobileFinder uses FTP as its transfer protocol, which provides more cross-platform compatibility in a single protocol, but unfortunately does require that Mac users supply their own FTP client such as Transmit or Cyberduck, since Finder itself provides read-only access to FTP servers. Opening MobileFinder presents a Finder-like interface, with pre-defined folders for Documents, Movies, Music and Pictures, as well as a folder of Sample Files. Each of these pre-defined folders may be renamed or deleted, either directly on the iPhone or iPod touch itself, or via an FTP connection.
To begin sharing files, tap the icon in the bottom-right corner, and a transfer status window is displayed, with a Start/Stop button that can be used to enable the FTP server portion of MobileFinder.
From the tabs at the bottom, instructions are provided for configuring your computer to access MobileFinder for Mac OS X, Windows XP, and Vista.
Transferring files to and from your iPhone or iPod touch with MobileFinder is simply a matter of following these instructions, which basically talk you through setting up a traditional FTP connection to MobileFinder. Note that no password security is available in MobileFinder, nor does the device prompt the user for individual connections—it simply operates as an anonymous FTP server whenever it is started, and users should therefore be cautious about leaving the file transfer portion enabled when on a non-secure Wi-Fi network, as any user will be able to access and browse the entire file system.
MobileFinder does provide some rudimentary security at a file and directory level, but this is made needlessly complex for the average user by trying to emulate standard Unix-style file permissions such as read, write and execute, which can be adjusted from the file or folder properties; these are displayed by tapping the blue arrow beside a file or folder entry.
Unfortunately, users without an understanding of the Unix file system will find this to be extremely confusing and non-intuitive, and in fact these settings are not even applied consistently with normal expectations. For instance, the removal of the Execute permission from a folder should prevent a user from navigating into that folder, but in reality it simply presents a list of files in the folder while not allowing these files to actually be read, either via MobileFinder or an FTP client. In addition, other than the files being displayed in a different color, no user feedback is provided—tapping on a file simply returns the user to the parent directory without any explanation.
Further, MobileFinder presents a fair bit of other internal OS X file system information for each file, such as owner, group, and Unix-style permissions. While this information may have been somewhat useful for advanced users when using MobileFinder as an application for jailbroken iPhones, it is almost entirely irrelevant for an official App Store application.
That having been said, MobileFinder does provide some very useful file management capabilities that are missing from other file storage apps, including the ability to move, copy, and delete any file or folder, the ability to create new folders and new text files, and even the ability to zip and unzip files directly on the device. All of these functions are accessed by tapping the Edit button at the top-right of any folder listing, at which point you may select several files and choose a function to apply to them from the menu bar at the bottom of the screen.
Another useful feature that MobileFinder provides is the ability to edit text documents directly on your device. Opening a text file will display an Edit button in the top-right corner, and tapping this button will bring up the on-screen keyboard so that you can edit the document.
Other common file types can be viewed directly on the device, including the usual supported formats such as Microsoft Office, PDF, and JPEG files. MobileFinder also provides support for iWork documents, although it insists that they be zipped first, which the device will offer to do for you.
Unfortunately, although MobileFinder offers some nice advanced features, it performed poorly during our testing. File transfers to and from the device were the slowest that we observed from any of the six applications we reviewed, taking up to twice as long. Part of this is due to its use of the less efficient FTP protocol, although even when compared to DataCase using FTP, MobileFinder was still noticeably slower. Further, MobileFinder is incapable of handling large PDF files at all. When attempting to view our 27 MB Free iPod + iPhone Book 4 reference document, it consistently failed with a “Low Memory” error:
Attempts to view our 9.5 MB 2008 iPod + iPhone Buyer’s Guide failed with a Low Memory error about 50% of the time as well, although it tended to work successfully immediately after a restart of the iPhone. More seriously, MobileFinder rebooted our device spontaneously when attempting to view larger files, whether or not it had been successful in displaying them. Repeated attempts to view large files almost invariably resulted in a complete spontaneous reboot of the iPhone. Exiting and reloading MobileFinder after a “Low Memory” error seemed to prevent this from happening, but it’s clear that there is a memory issue in MobileFinder somewhere that is causing problems.
Further, several times after encountering a “Low Memory” error while trying to perform functions such as compressing or uncompressing files, MobileFinder took us to the root of the iPhone file system instead of its normal “Home” folder—an area that no official app should be permitted access to. From there, we were free and clear to wander through all of the normally inaccessible files and folders that live within the iPhone operating system. It should be noted that this occurred on two different iPhone 3G units, neither of which have been jailbroken, but oddly could not be reproduced on an original iPhone that previously had been.
Finally, several times after encountering several “Low Memory” errors, each the iPhone 3G units we were testing with spontaneously rebooted and never came back, instead hanging at the Apple logo. This necessitated full restores of the iPhones by forcing them into the special DFU restoration mode, a process that many end users would not know how to undertake, and would more likely wind up at a Genius Bar to resolve. MobileFinder’s behavior in this regard would seem a clear indication that Apple is not testing or vetting App Store applications as thoroughly as users might expect, since bugs providing access to the entire iPhone file system and causing the iPhone to hang on reboot are issues that one would expect Apple to identify during their testing and certification process.
While MobileFinder has a great deal of potential as a more full-featured iPhone or iPod touch file management application, it seems clear that it’s going to need to drop its jailbreak roots and be further refined as an official application before it’s ready for prime time. The current level of complexity and the serious stability and reliability issues make this an app that we can only recommend you stay away from, at least until the developer provides an update that will address some of these issues. As much as there may be here to like, messing up the iPhone to a DFU restoration level multiple times qualifies an app for our lowest possible rating. iLounge Rating: F.
TouchFS
Regal Media’s TouchFS ($15) is another WebDAV based file storage app, similar in concept and design to Files, but with a premium price tag—one of the highest we’ve seen yet for an iPhone app. When running, TouchFS presents your iPhone or iPod touch to your computer as a WebDAV server, which you can connect to directly from Finder or Windows Explorer, albeit manually. Starting TouchFS will immediately take you to a file listing screen with a folder of sample files and a “readme” file pre-loaded onto your device.
As with most of the other file storage apps, TouchFS immediately starts listening as a WebDAV server as soon as it’s started, although you’ll need to hit the “Options” button to find the IP address of your device if you do not already know it.
In addition to showing you the URL that you can use to connect to WebDAV from Finder or Windows Explorer, this screen also provides the option to turn off the WebDAV server entirely, change the listening port number, or enable user and password authentication. From a client access point of view, TouchFS actually combines the authentication features of both Files and DataCase. With TouchFS, if you do not enable authentication, no password is required to connect, but you must authorize each connection directly on your iPhone or iPod touch.
If authentication is enabled, the specified user name and password will be required to establish a WebDAV connection from your computer, but you will not need to authorize the connection on the device itself. Unfortunately, unlike Files or DataCase, there are no “mixed” authentication options available nor is there any multi-volume support—you must choose one method or the other and there is no way to set up different storage areas with different security.
Once connected from your computer, file management is handled through Finder or Windows Explorer in the same way as with the Files application reviewed earlier. TouchFS offers a fairly useful built-in help system which is accessed by tapping on the question mark icon in the bottom right corner of the main TouchFS screen.
Information on how to connect from your computer and how to use TouchFS is included here, and the directions are quite concise, although are static documents rather than being being dynamically generated to include your own configuration information. For example, the instructions for connecting to TouchFS from your Mac will include a sample IP address and instructions for where to within TouchFS to find the actual IP address of your specific device. Despite its other serious flaws, we much preferred MobileFinder’s help system which included your actual IP address in the appropriate locations.
Files transferred to the device will appear on the main screen, with any sub-folders sorted at the top of the listing. TouchFS does not provide any file management capabilities on the device at all—if you want to delete a file you will need to reconnect from Finder or Windows Explorer in order to do so.
Tapping on a supported file will open it for viewing. TouchFS supports viewing of JPG, PDF, HTML, text, and Microsoft Office Word, Excel, and Powerpoint documents, as well as any video or audio file that could otherwise be synced to the device from iTunes.
iWork support with TouchFS is a little more complicated: the latest version indicates that iWork Pages and Numbers documents are supported as long as they have been saved with previews enabled. If so, these can be viewed in the same way as any other document, and unlike Files or MobileFinder there is no need to zip them up first. Attempting to view a Pages or Numbers files that has not been saved with previews enabled will display a message indicating as much.
Note that other storage apps we’ve reviewed here do not require that iWork documents be saved with previews to enable viewing, although they do require that your files be zipped first, with the only exception being FileMagnet, which presumably pre-processes iWork documents through its own desktop file transfer application. It should also be noted that TouchFS does not support iWork Keynote presentations at all, so these will need to be saved in a Microsoft Powerpoint format if you wish to view them on your device.
Documents may be viewed in portrait or landscape orientation by rotating your device, which rotates the entire TouchFS interface.
One odd inconsistency we did note with this: you cannot switch the normal file listing interface into a landscape orientation by rotating the device from the main screen, but if you return from viewing a document in landscape view, the TouchFS interface will also be presented in landscape mode until you rotate your device back into portrait orientation.
TouchFS also behaves a little bit differently when viewing text files on your device.