A universal font of size 7 for the HP49G/HP49G+

What is New?

Version 9.2003: This html-document replaces Lfont.txt.

First Version from July 2003 had no version number.

Lfont.F is a self-decompressing font code, particularly helpful for writing logical and other mathematical formulas. Since it allows to add sub- and super-scripts and knows nearly all Greek letters, it is useful also for general purposes. Standard letters and symbols of Lfont.F have a much better quality than those of the builtin FONT7. Hence, it may replace FONT7 and can indeed be your default font, see below. Press Lfont.F and you'll see Ft7_7 LogicFnt on the stack. Now press DownArrow to have a first glance at the font. Browsing with rightshift DownArrow and UpArrow you see the two screens as shown in the two 49+ screen-shots. The first 10 characters serve as superscripts, the characters with numbers 16 through 25 as subscripts.

Upper part of fontbrowser on Lfont.FLower part of the fontbrowser on Lfont.F

Viewing the first 32 characters as symbols is besides in the font browser possible only inside strings because normally these characters are invisible and used for various tasks in text processing. Using strings, you may write the most complex formulas from higher mathematics and logics. With Lfont it is possible to create not only single formulas but to write whole scientific papers if you have the patience to do so. The left-hand screen shows a small example, the power set axiom of Ernst Zermelo in formalized set theory. In words: To each set x there exist a set y which contains each subset of x as an element. The smallest such set y is called the power set of x. Let us mention that all non-standard characters of Lfont, including the first 32, can also appear inside a name, for instance. Simply make an illegal name from a corresponding string with S~N from library 256, say. Clearly, these names are readable only as long as Lfont.F is your actual font.

There are various methods to make Lfont.F your default font. A warmstart sets normally the default FONT8 but this behaviour can be changed by storing   Lfont.F FONT in the STARTUP file or adding this to STARTUP in case STARTUP already exist in HOME. Due to compression, Lfont.7 cannot be detected by the builtin font browser in MODE/DISP. Either uncompress Lfont.F and overwrite the code in Lfont.F by the font itself and use the builtin font browser, or store the uncompressed code in port 2 under the name Lfont.F and use the font browser of the library Fontman. In the first case you loose about 1 kB. In the second case, Lfont.F lives as a self-decompressing code in Port2 and you loose nothing execept a few bytes for the library Fontman. But this library is useful anyway. Here the suffix .F is important, otherwise the font selector of Fontman would not detect Lfont.F.

Lfont.zip includes also a key-assignment called LFKEY. Very useful provided Keyman is on your 49 and the ROM is not older than 19-6. LFKEY assigns the rightshiftHold CHARS key (42.31) as follows: If rightshift is hold while pressing CHARS sets the string processing menu 62 as usual. But if rightshift is still hold and pressing CHARS a bit longer, the current font toggles with Lfont.F. Note that this font toggling works perfectly also in Edit mode. The blinking cursor of Lfont.F differs somewhat from the default cursor. With fontsize 7 there are 6 stack levels displayed on the 49 and 8 stack levels on the 49+. Once the key is assigned, LFKEY can be purged.

Lfont.F can also be modified. Fontman supports such a project. You may do it either for yourself only, or with the aim of publishing a modification of Lfont.F. In the latter case the internal font-parameter of Lfont.F have to be changed. How to do this is described in detail in Fontman.htm. We propose to publish such a font as a self-decompressed code, similar to Lfont.F. Such a code can only be created with the BZ-tools of OT49. In the same way the self-decompressing code of Lfont.F was made.

Wolfgang Rautenberg

 raut@math.fu-berlin.de     www.math.fu-berlin.de/usr/raut