Re: Simple questions for the 50g Message #3 Posted by James M. Prange (Michigan) on 22 Nov 2006, 12:32 p.m., in response to message #2 by Crawl
For your #1, it seems that your manual must (unfortunately) be showing the menu for ALG mode, which, as far as I'm concerned, is best avoided.
A few more suggestions for your #2.

If a "zint" (arbitrary length exact integer) has more than 12 digits (exclusive of trailing zeros), then converting it to a "real number" (floating point decimal number) rounds it to a decimal approximation with a 12digit mantissa. If a zint has more than 500 digits (including trailing zeros), then converting it to a real changes it to 9.99999999999E499 or 9.99999999999E499.

Any number entered with a "fraction mark" ("decimal point") is always compiled as a real.

In approximate mode, entered numbers, even without fraction marks, are always compiled as reals.

In exact mode, numbers entered entered with fraction marks are compiled as reals, and numbers without fraction marks are compiled as zints.

When "ASCII" ("Text") source code files are downloaded, the same rules for compiling numbers as reals or zints apply. If the file originated on a 49 series or was composed in a text editor for the 49 series, it's usually best to be in exact mode while downloading, to avoid having zints compiled as reals. If the file originated on a 48 series (which doesn't have zints) or was composed in a text editor for the 48 series, it's usually best to be in approximate mode while downloading, to avoid having the reals compiled as zints.

When "executing" a character string with the STR\> or OBJ\> command, the same rules for compiling numbers as reals or zints apply.

If you have a list, algebraic object, or program which includes several zints on level 1, then you can change them all to reals by switching to approximate mode, pressing LeftShift CursorDown to invoke the EDIT command (or just CursorDown to invoke the EDITB command will do for lists or programs), don't explicitly change anything, and press ENTER to have them all compiled as reals.

You can change a real to a zint by editing out the fraction mark and pressing the ENTER key in exact mode.

The I\>R command converts a zint to a real.

The R\>I command converts an integer valued real to a zint. If the real has a fractional part, R\>I errors out; you can use 0 RND, IP, FLOOR, or CEIL to get an integer valued real from a real with a fractional part.

If you set flag 3 (Function > num), then any calculation with an algebraic object attempts to evaluate the expression all the way to a real. Effectively, it automatically includes the \>NUM command. If it can't be evaluated to a real (such as when it includes an undefined variable), then an error occurs.

If you set flag 2 (Constant > num), then a builtin constant such as \pi, e, i, MAXR, or MINR is automatically evaluated to its real (or complex) value.

\>NUM is a command, so it can also be used in a program.

You can also force approximate mode by setting flag 105, or exact mode by clearing flag 105, which can be done within a program.
For your #3, by default, the 49 series turns itself off after 5 minutes of inactivity, but this can be changed by storing a binary integer in the reserved variable 'TOFF' (I surmise from Timed OFF). You can have a 'TOFF' in as many directories as you like; the first one found in the current path will be used. The value in TOFF represents the number of ticks (1 second = 8192, or 2^13, or #2000h ticks) of inactivity before the calculator turns off. For example, if you want a 60 second timed off, #2000h 60 * gives me #78000h (or #491520d, etc.) so store that binary integer in 'TOFF'.
In case you set TOFF very low, there's a minimum of a 5second timed off as a "safety net", so that you have time to purge, rename, or modify TOFF before the calculator turns itself off.
[Edit: The maximum is not 2^31 (#80000000h) ticks.]
There's also a maximum of 2^311 (#7FFFFFFFh, the maximum 31bit value) ticks (a little over 3 days) for TOFF, which I surmise has to do with the calculator's maximum time without doing some "housekeeping" with its time system. Even with the calculator off, it will very briefly "wake itself up" to take care of the time system housekeeping after that long.
Regards, James
Edited: 23 Nov 2006, 11:00 p.m.
