PRINTF is a way to format printed output. It can be as simple a short string or quite complex specifying field sizes and pad characters for a number. This routine is written in C and is part of the firmware. As of 8.11 firmware BASIC programs can access this powerful C subroutine.
Rather than duplicate the documentation of PRINTF, there is a great deal of information for printf in documentation for C such as
PRINTF in the firmware supports c (BYTE), s (STRING), d (decimal INTEGER), x or X for (hex INTEGER), e, E, f, g, or G (for SINGLE).
The G format is used by the ARMbasic PRINT, it differs a little from the G format of C. It displays 0.0 or the range 0.1000000 through 9999999. and outside that it uses D.DDDDDDE+DD and the negative values as well.
Pad characters of 0 or space can be added to fill out LENGTH or WIDTH and PRECISION. PRECISION is limited to 0 to 8 characters.
To add CR <carriage return> to the output printed, either use PRINT or print a %c with a value of 13