Dropbox.

Dropbox is ideal for storing and sending uncompressed files.

Our friend popped in last week for a bit of advice on using his new iPad. He wanted to get his photos from the PC onto the iPad. ''Dropbox,'' we said. And how can he send uncompressed photos to his family and friends so that they can print them? Dropbox. In fact, any large files that need moving and copying from one device to another need Dropbox.

Dropbox is a mysterious thing in the sky where you store files and share them. (We do apologise to those readers for whom this is akin to teaching granny to suck eggs. Our excuse is that we are amazed there are still people who don't know about this free storage and transmission service.)

The first 2GB of space is free. You can get more free space by persuading friends to join up. And we just received another 25GB by buying an HTC One S phone. Once you've joined at dropbox.com you then set up Dropbox on all your other devices - PCs, pads and phones. (It is an app for phadlets.) It is like having a network with its hub in the cloud.

We use Dropbox to shuffle files between our domestic devices, and for sending files that are too large for polite email transmission.

On a PC, Dropbox installs an icon in the tray (bottom-right corner). Double click on that and it opens the Dropbox folder. Sub-folders appear by default. Open any sub-folder and, using the right-side mouse button, drag and drop a file into it, choosing Copy from the options. If you use the left button, it will Move the file, deleting the source.

On a Mac, the Dropbox icon appears in the top-right section of the toolbar. Once the file is in Dropbox, the upload to the cloud starts automatically and it is complete when a white-on-green tick appears under the file icon. Now it is ready for sharing.

Open dropbox.com in a browser and the same folder structure appears as on the computer. Navigate to the file to be shared, right click on it and choose Get Link. A window pops up, into which you enter an email address. Dropbox knows about your address books, so the address will usually be completed automatically.

And here's the killer Dropbox feature - the automatic web photo gallery. The default Photos folder has a special function. Create a sub-folder inside Photos for ''Paris Holiday 2012'' (or whatever) and put all your best pictures into it. When it is finished uploading (white tick), right click on the folder, go down to Dropbox and click on Get Link from the options. Email the link and the recipient will get a gallery of your photos. And all for nothing! However, as with all cloud services, we do not treat Dropbox as 100 per cent secure.