To see sample of one font on Datadisk, R DDFONT -- Most of the fonts are located
  on *.FNT[XGP,SYS].
To create a new font or edit characters in an existing font, R EDFONT (many bugs).
To edit and examine the magic parameters of a font, RU FONT[S,BH].
To merge two fonts, selecting characters from each, R COMBIN.
To binary-edit any file, such as a font file, R FILDDT (experts only).
To compile a font, RUN UFC[XGP,SYS].  UFC.REG[UP,DOC] explains what it compiling
  a font means, and why it's good for you.
Some of the above programs append the ".FNT[XGP,SYS]" if you leave it out, but all
  of them (I think) will accept the complete file name if you type it all.