Storing and transferring data
This information sheet looks at the basics of data storage and file transfer.
Storing files on disk
A standard floppy disk holds 1.44 MB of data, but there are higher capacity solutions that hold around 100-200MB of data, such as Iomega Zip disks, the LS-120 and the "A Drive". These are proprietary formats, for which you will need a purpose-made hardware drive.
Systems that hold around 2GB and more are available on other proprietary disk, cartridge and tape systems, but are used mainly for archiving and back-up in case of system failures and data loss.
CD recorders, with "write-once" and rewritable CDs holding 650MB, are now an affordable medium for data storage and transfer. DVD writers, holding around six times as much and suitable for large video files (for example three hour full screen feature films), will become more affordable in time.
Most text, database or spreadsheet files can be compressed or "zipped" using WinZip or similar software to fit onto a floppy disk. The degree of compression and hence the size of file that can be stored on a single disk varies according to the size and format of the original file.
Many graphics files, for example gifs and jpgs, are already compressed and will not compress further. However, some programs will automatically break apart and recombine files that are too large for one disk.
Are you compatible?
The easiest way to transfer a file is to give it to someone on a disk. But to be able to use the transferred file the hardware, operating systems and application software of the recipient must be compatible. There can even be compatibility problems between different versions of one program, as between Microsoft Word 95 and 97 - a document in Word 97 cannot be read, let alone edited, by Word 95 - however free ‘reader’ software is available for download.
PCs and Microsoft software are the best bet for compatibility with customers and suppliers, but if you intend regularly to interchange files or communicate by computer with another organisation, ask them what systems they use and make sure you can be compatible before making any investment.
Sending files using e-mail
Files can be attached to an e-mail message and sent either zipped or unzipped. A standard telephone and a modem is fine for limited size text documents, but it will take about four minutes to transfer a 1MB file, compared to one minute using two channel ISDN. Broadband connections can work around 10 times faster depending on how congested the Internet is at the time.
Some ISDN cards/terminal adaptors and software packages will automatically compress and decompress data when communicating with a compatible package using an appropriate protocol.
Sending files over the Internet using file transfer
When you start to look at sending large files such as graphics, CAD or multimedia information, or even large spreadsheets and databases, it is worth thinking about using a file transfer program.
File transfer protocol (FTP) is used for downloading software from the Internet - you don’t know you are using it because it is now usually a function of the browser software - and for uploading web pages to a website host server, but it can also be used for transferring files between ordinary Internet users.
Files can be sent via FTP to an Internet Service Provider's server space (a mailbox for files), where the intended recipient can download it using the relevant FTP server address and a password.
Alternatively, if both parties are connected to the Internet at the same time, the sender can act as the server, using one of several free FTP software packages, and the recipient as the client, simply dialling the server's telephone number to download the file.
Using a 56K modem and a standard telephone line it will take around 2 minutes 40 seconds to download 1MB, but around four minutes per MB to send, as most modems are only capable of upload at 33.6kbps. It is also unlikely that you will get maximum bandwidth end to end, due to telephone cabling losses and congestion at various Internet bottlenecks.
Point-to-point file transfer using ISDN
The print and graphic arts industries, which regularly transmit large and graphics-rich files, use ISDN for point-to-point file transfer. This has the advantage of faster transfer times - using two channels of ISDN, which aggregated provide 128kbps bandwidth, you can send around 1MB per minute, but using two channels so twice the cost.
With compression of suitable file formats and compatible hardware/software at each end, these data rates can be significantly increased. Specialist ISDN software/hardware packages for file transfer have been developed to cater for this market, some of which claim to double or even treble file transfer rates.
The whole file transfer process in the graphic arts industry could change with the advent of specialist virtual private networks (VPNs). VPNs are managed networks. The sender connects to the network and sends the file to the network address of the recipient. The network supplier then takes responsibility for making sure that the file gets to the addressee. This saves senders from having to hit a "window" of time when the receiver's equipment is not engaged on another call.
Receivers can choose the order in which they want to download files - so they are not engaged receiving a non-urgent file while waiting for the opportunity to download another which has a more pressing deadline.
Several file transfer programs can be downloaded free of charge from ZDNet's download site.
Reviewed January 2011
last updated : 21/01/2011
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