Altered states Buying a disc drive is not always a bed of roses as those with an extensive collection of software on cassette, will find out when they upgrade to disc. Transferring commercial programs from tape to disc so they can be loaded quickly can pose more than a few problems. For a start, protected Basic programs and loaders are impossible for the inexperienced programmer to stop and list. This means they cannot be saved on to disc. Another problem is binary files which contain machine-code programs or routines which, because they are loaded high in memory are incompatible with the disc operating system. When the Amstrad DD-1 disc interface is connected to the Amstrad CPC464, the memory pool is reduced by 1284 bytes. This space is used by the disc operating system. Some of the early software for the 464, uses machine-code that occupies all or part of this reserved area. What actually happens when you try to load code that resides high in memory is that, as soon as the incoming binary starts to overwrite this 1284 byte area, the disc operating system crashes and usually results in a system reset. Transmit is a disc utility which gives 11 commands that make the task of tape to disc transfer literally child's play. The Trans n Auto command transfers n programs from disc to tape automatically, where n can be any number in the range 0-255. However this command can only be used if you are sure that the program(s) will run satisfactory when loaded from the disc. The effectively rules out commercially-written software which, because it is designed to be loaded from cassette, use filenames that would cause an error when used with AmsDOS (Run”,Run "!" Run "!Loader"'). The Trans n command on the other hand is extremely clever. Not only will it transfer basic programs, machine-code loaders etc, but when it comes across a binary file that would overwrite the area of memory used by the DOS, it will stop and warn you of the impending danger. You axe then asked if you wish to relocate the incoming code. Responding lY' to the prompt will result in the machine-code being loaded into the highest 'safe* location in memory with a short relocator routine being added to the beginning of the original code. When this code is subsequently run, the lowered block of machine-code will be restored to its original position before being executed. Another command, Info, reads file headers from the disc, and prints to the selected output device, screen or printer: file name, file type, location, length and execution address if any, for all of the files on the disc. Some of the commands merely duplicate the commands already available from AmsDOS, such as Dir, Era, Ren and CPM, the main advantage being that they are available direct from within Transmat which is useful, and. in the case of Era and Ren, there is no need for the Rsxcommand prefix Neither is there any need to put the filename into a string variable: just type Era: filename or Ren: newname = oldname. I found the program invaluable. It performs extremely well and I have yet to come across a program that is impossible to transfer on to disc using Transmat A couple of points that irritated me about the program were firstly, on loading Transmat the screen colours are changed to black ink on a light background, not the best choice for extended use in my opinion. And the command CPM allows you to boot CP/M from within Transmat without providing no way of reversing the process. A short Transmat. Com supplied to allow movement between CP/M and Transmat, would have saved Pnde the trouble of including Ren, Era, and Dir in to their utility. An invaluable aid for those with newly acquired disc drives. Geoff Baldwin, Popular Computing Weekly
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