Scor­pio News

and didn’t have to curse very many times, but I have to admit I was surprised at having to do this. Then I thought how much more money Hisoft might have wanted from me if they had had to do the job, and I decided it was a good way to update a manual…

Modern Hisoft manuals are good, and full of useful advice for first time users, without having too much of it. (The old ones, as I remember, were rather hard work to use and to read; we all have to start somewhere.) This manual contains a section describing the improvements over HP4, which corresponds very closely with what I wrote ages ago about the parts of Pascal that HP4 couldn’t do, although I don’t suppose for a moment that I had anything to do with this. For instance Variant records are now possible, as are files of type another than text. I have not yet needed to use a variant, but I used to hate having to save integers, reals and booleans as text.

You still can’t have files of files, but who wants then? (Cue for at least twenty angry letter from academics.) Another new feature is that the compiler can now cope with such bigger programs, because it saves each routine to disk as it is compiled. The symbol table is twice as big, too, not that I ever managed to fill the old one. Reserved words can now be in lower case, if you like, Apple Pascal always used to look nice because of that, but it isn’t vital, just a thoughtful touch.

The manual gives detailed descriptions of the syntax and semantics expected by the compiler, and describes the various predefined identifiers that are available to the programmer. Once again, I will save a lot of space by not copying out a great list of these, as they are almost all exactly the same as any other Pascal. Instead I’ll attempt to restrict myself to writing about the interesting, or changed, parts.

A major new feature of the system supplied is the appearance of a menu at the start of operations. This offers a choice of editing a program, compiling it, running it, executing it (which means compile AND then run) or quitting. It is rather like the options offered by p-systems Pascals. The editor is the now standard Hisoft program editor that I have described before, and can of course be modified for the SVC as mentioned in the last article. This time, however, when you exit from editing, the menu reappears, and you can compile the program from there with a single keypress. This really does save a lot of tine, compared with the long commands one had to enter to use earlier versions of the compiler, especially if one is being naughty and programming and debugging at the keyboard. Slapped wrist from Niklaus Wirth if he catches you at it. If by some mysterious chance your program contains a syntax error, and the compiler spots it, you no longer get a mystery number on the screen and and have to dive for the manual. The error messages are in English. Yet another major advance, not that I ever see error messages, of course…

The New, Mark Dispose and Release procedures have been changed so that they now conform with Wirth’s standard, and this allows more sophisticated use of dynamic variables, without which fancy list handling is out of the the question. You can do astounding things with lists, dear BASIC users. The Inline and User procedures allow you to put in machine code, if necessary. This is, of course, disgusting to all who regard programming as an abstract art form. Have you noticed how slow their programs are? Peek, Poke, Inp and Out give you access directly to memory and Z80 ports, and are consequently vital if you want to write programs that work, say, a Plato, or indeed, any of the other 80-BUS boards that expect to be accessed via Z80 ports.

The most tremendously useful of all the new procedures, however, is Chain. It loads and runs another program, so now it is possible to write vast systems of programs, way beyond the size of memory. And they don’t have to communicate with each other in the clumsy way I once advocated, by passing data in files, either. As long as the variables used in more than one program are global variables, and are declared in the same order in each program, they will stay in memory ready for the next program to use them. The best way to do this, says the manual, is to store all these declarations in a file, and use the compiler’s ‘include’ option to read in this file as each program is compiled. Thhis