The Amstrad grows up at last with the arrival of the DDI-1 disk system. And it's excellent value for money, says Bryan Skinner

Amstrad's disk drive package (called DDI-1) is a steal: for just under £200 you get a 3in disk drive, CP/M 2.2, DR Logo and Basic extensions to allow you to use the disk as a fast tape system. You'd be lucky to get a disk drive and interface for that price for any other home micro you care to name.

The disks are 'flippy-floppies' - you turn them over to use the other side, giving each disk 340K of storage. The 3in format is also neat, you can literally chuck them across the room without damage and you don't have to be too careful about storage.

Setting up is a doddle, as you might expect from a plug-in-and-go machine. Just plug in the ROM cartridge, connect the drive to the ribbon cable, fix a plug on the power cable and you're in business. Drives can be piggy-backed, for which Amstrad thoughtfully provides a second connector on the ribbon.

You can swap between tape and disk handling using the bar command extensions of the Basic operating system. Thus |tape switches to tape handling, |disc switches back to disk. From then on, all the tape-handling commands you're used to (except speed write, of course) will act on whichever device you've selected. Some commands require the @ parameter, as in |ERA, @A$ which deletes the file name contained in the string variable.

It's nice being able to switch into CP/M with just |CPM, and back to (almost) normal with AMSDOS. Because AMSDOS is designed to complement CP/M, CAT will produce almost the same as DIR *.*, i.e. display file names, their extensions and sizes, as well as the amount of free space left on disk. Many of the AMSDOS commands mimic CP/M commands, a neat touch because you don't have to switch into CP/M to rename files or switch areas.

There's only one manual and this covers just about everything from wiring the mains plug to Jump Block re-interception by the user, and all in less than 100 pages. Like the 464's manual, it is clear, well-written and detailed, but short on examples. There are sections on setting up 'turnkey' disks and installing CP/M software. The latter would be useful in the unlikely event of software distributors making CP/M programs available on Amstrad format disks, though with an RS232 interface you might be able to download software from another machine.

There are some fascinating snippets of information: "The BIOS supports three different disk formats: SYSTEM format, DATA only format and IBM format." Apparently, the IBM format is the same as that used on IBM PCs running CP/M and is intended for "specialist use". The plot thickens...

All formats have common parameters e.g. 512 bytes per physical sector and space for 64 directory entries. DATA only can be used if you never intend to use a disk with CP/M. It makes a little extra disk space available because no data is stored on the system tracks.

Where the manual falls down is in CP/M detail. For example, user areas are said to be "for specialist use only, consult CP/M reference manual" - you have to buy that as an extra.

Dr. Logo is dealt with in 24 pages, detailing what each command does but there are no pictures. There are words like 'buttonp' and 'keyp' for monitoring joystick and keyboard, and sound commands (unique to this implementation) which follow the parameter passing pattern of Basic.

The drive is slim but long. With width of main unit of the Amstrad and the large monitor, the kit takes up a lot of desk space. There are dire warnings about putting the drive too near the left of the monitor.

The system is quite fast - reading in the digits 1 to 1000 takes about nine seconds using an integer FOR...NEXT loop. Writing the data to a file takes slightly longer because it has to be verified after each write operation. It's a joy to load whole screens of information and long programs in just a few seconds.

However, it's a crying shame random access files aren't supported. Data files under Basic/AMSDOS are sequential. This means, if you want to write a database in Basic, you're going to come across lots of problems. To read in the Nth entry, you'll have to read in all preceding N-1 entries first. Sequential files also mean that inserting an entry, or sorting and rewriting entries will be a real pain (and slow). And if the file size exceeds available RAM, you simply won't be able to!

The DDI-1 takes the Amstrad out of the home computer category and into the bottom end of serious use. With a priinter, and when suitable software becomes available, it will be quite feasible to run accounting packages, stock management systems, and do all the word processing required of a small business.

For the home user, the addition of the DDI-1 means users can get acquainted with the grandaddy of operating systems, making the transistion to 'real' micros much easier. Amstrad is to be congratulated for using the 3in format, bundling CP/M and in particular keeping the price low. A bargain.

Features 5/5
Documentation 3/5
Performance 4/5
Overall value 5/5