Is the Astron Card the next major storage revolution or a nine days wonder? Simon Williams has been giving the question some thought.

In the last ten years or so, small rectangles of plastic have made larger and larger inroads into our daily lives. Credit cards from banks have increased the convenience of shopping, those from individual stores have offered instant credit to spread the cost of purchases. The information these cards carry is embossed in the plastic itself and read by running an inked roller across the raised type.

The banks have gone further than this with the introduction of automatic cash dispensers. The information on cash cards is encoded into magnetic strips across their backs. The dispenser can read this code and verify the card before allowing the user to withdraw money from the machine at any time.

Even with the autobank card, though, the amount of information which can be stored is relatively small. The latest evolution of the plastic card offers far greater potential, and may well prove to be the most important computer innovation since the advent of the floppy disc. In this country, one of the leading exponents of 'chip-on-a-card' technology is the disc drive manufacturer, Cumana, and you can try out ''Astron' cards, as the company calls them, with an inexpensive adaptor for your BBC Micro or Master.

The BBC Micro adaptor consists of a small plastic box connected to the micro by a half metre length of ribbon cable. The adaptor plugs into any vacant ROM socket, and can be used from an expansion board as well as from the main p.c.b. The cable has to come out between the case halves or through the ventilation slot at the rear. It's a shame an insert couldn't be made for an Astron edge connector to fit in the speech ROM hole to the left of the keyboard.

Inside the box there is a small circuit board and the card socket itself, which is similar to an edge connector, but with guides at either end to ease the insertion of the card. The adaptor for the Master fits into the cartridge port, and is rather more expensive than the BBC unit.

The Astron card is a credit card-sized piece of 2mm thick plastic, with two rows of gold-plated contacts at one end. Embedded in the plastic is a ROM, RAM or EPROM chip, much like the chips inside 'normal' 28 pin ROM packages. The card is very durable, and quite tough enough to slip in a wallet or pocket. The system could be further miniaturised, as the chip is mounted close to the contacts, and a lot of the length of the card is there to take advertising or instructions.

Once the adaptor has been connected to the micro (with the power switched off), you insert the card and switch on. No matter which socket the adaptor is plugged into, it takes priority and the title screen for the supplied Superior Software game comes up on your screen. To be a direct replacement for a disc, you should really be able to insert and extract cards with your micro on, and to select them with the ROM filing system. Perhaps this will come later.

The game itself, 'Star Striker', is a copy of the old arcade favourite 'Moon Cresta', where you plough your way through wave after wave of aliens with a three tier ship that is forever separating and rejoining. If anything, the game is rather too easy to play, and once you've been through half a dozen waves they start to repeat. The game does serve to point out the advantages of the Astron card, though: instant loading, no disc errors and the possibility of holding many kilobytes in your pocket. So far, the Astron card has moved very slowly in gaining acceptance from software houses and the public. It's a bit of a 'chicken and egg' problem, as the average micro-user will only show passing interest while there is a shortage of software in the new medium, and software produces are reluctant to invest in another form of data storage while there are few potential buyers.

The two main suppliers to have expressed interest so far are Superior Software, who are to market several of their BBC Micro games on Astron cards at the same price as the disc version, and ACP, who can provide a selection of their utilities 'on-card'.

The drawback at the moment is the price of the cards themselves. Although 8K and 16K EPROM cards are available for between £5 and £10, this compares unfavourably with the 28-pin chip variety. The advantages of portability and robustness have to be weighed against the extra cost. Perhaps for this reason, Cumana are concentrating on the serious software market for their cards. With business and utility software, the extra cost of the card represents a smaller proportion of the total. The company is also looking at other target micros, and there are rumours that the portable machine from Clive Sinclair's new company may make use of them.

Perhaps the most exciting feature of the Astron card is the development of large capacity ROM and RAM cards. Cards of up to half a Megabyte are already available (at a price) and 1 and 2 Megabyte ones are expected soon. Imagine carrying the equivalent of a hard disc full of data on five credit cards! RAM cards will be battery-backed with a five year lithium cell and Cumana are developing a DFS-like filing system to allow RAM cards to be used as discs.

At present, the price of the cards probably restricts them to EPROM chip replacements, where their added convenience and portability are assets. If Cumana can get enough adaptors onto the market, as they deserve to, to be able to offset the development costs of the larger ROM and RAM cards, the Astron card could take over as a primary means of data storage.

The reasonable cost of the adaptor gives you the chance to try the new technology for yourself. And you can always zap a few aliens while you're at it!