Returns, as -1, 0 or 1, the signal of the given numerical value
Implemented by: dartmouth3, ansimin, hptsb, decbasic, Altair, a2int, Applesoft, TI994, CBM, Atari, msatari, level2, trscolor, colormc, zx81, spectrum, BBC, GWBASIC, MSX, bwbasic, bw32, ABasiC, QBasic, VBDOS, FreeBASIC, Gambas, ugBASIC, minibasicjs
With variations:
Also written as: