ASCII data and strings
Message #8 Posted by Vieira, Luiz C. (Brazil) on 7 Feb 2003, 3:54 p.m.,
in response to message #7 by Christof
Hi;
I remember the first time I get into contact with the HP41's X-Functions/memory module and the X-memory file concept. Program and data files were easy to relate with existing HP41 resources, but the ASCII files were beyond the HP41's hability to handle ASCII strings. The ALPHA register is able to hold 24 characters but any numbered register can hold only six characteres of an ALPHA string. Manipulating ALPHA strings with the basic HP41 functions' set is not easy: ARCL, ASTO and ASHF allow the handling of six characters at a time, and to handle one single character demands a bit of "juggling". The X-Functions set added not only some powerfull ALPHA manipulating functions - XTOA, ATOX, AROT, ALENG, ANUM, - but also some ASCII file handlers - CRFLAS, INSREC, GETREC, INSCHR, APPCHR, GETCHR and others (I'm writing by heart, if there are erros, please, correct me). And I thought: "What are these functions for?" Later, when I read about the HPIL and all HPIL-compatible devices and measurement instruments that could be connected and controlled by the HP41, I understood that ASCII strings were primarily dedicated to hold and handle ASCII data received from and send to external devices. One can handle ASCII data with a series of programs, but viewing ASCII strings in large texts by the 41's LCD is painfull. One specific HPIL device is the TV Link and allos ASCII files to be shown as complete text, but specific programs must br written to do so.
The HP42S has the lack for I/O activity, so ASCII files lost their space and only ALPHA strings prevail. Functions like ALENG, ANUM, XTOA and ATOX (plus the very welcome AIP) were kept, but there are no specific places (variable types or files) to hold large, contiguous ASCII sequences, that must be broken into sets of six characters each, so they can be stored in numbered registers, variables or matrix elements. Complex matrices and complex variables will need double the space of their real-only counterparts, but will still hold only six characters for each valid position.
I believe Christof's is a very well elaborated program that allows this ASCII-data handling and holding abilities in the HP42. I hope we can see it soon, because this is a very good way to use large messages organized in sort of an data bank, easing ALPHA manipulation.
Cheers.
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