$ whois forth

Forth

first released in 1970 · by Charles H. Moore

$ guessprog --inspect forth

year: 1970
paradigm: concatenative
family: forth
memory: stack based
binding: dynamic
safety: weak

FORTH(7)

AUTHORS: Charles H. Moore
HISTORY: Charles "Chuck" Moore developed Forth during the 1960s as a personal toolkit, and around 1970 used it at the US National Radio Astronomy Observatory to control radio telescopes. Forth is stack based and extensible: programs are built by defining new "words" in terms of existing ones, all in reverse Polish notation. It fits in a few kilobytes, which made it popular on early microcomputers and embedded hardware. Moore meant to call it "Fourth", for a fourth-generation language, but the IBM 1130 he used allowed only five-character file names.
USAGE: Forth is a niche language today, used in some embedded systems, bootloaders and hobbyist projects. Its best-known industrial use was Open Firmware, the boot firmware of Sun workstations and PowerPC Macs.
SEE ALSO: Forth on Wikipedia ↗

$ cat squares.fs

\ Words are defined with : and ended with ;
: square ( n -- n*n )  dup * ;
: sum-of-squares ( a b -- n )  square swap square + ;

3 4 sum-of-squares .   \ prints 25

: countdown ( n -- )
  begin  dup .  1-  dup 0= until  drop ;

5 countdown            \ prints 5 4 3 2 1