On Sun, May 15, 2022, 11:45 AM Undiscussed Horrific Abuse, One Victim
   of Many <[1]gmkarl@gmail.com> wrote:

   $ tput cup 2 2 | hd
   00000000  1b 5b 33 3b 33 48                                 |.[3;3H|
   00000006
   $ tput cup 4 5 | hd
   00000000  1b 5b 35 3b 36 48                                 |.[5;6H|
   00000006
   printf("\x1b\x5b%d;%dH", y, x);

   #include <stdio.h>
   typedef struct pt {
     int x;
     int y;
   } pt;
   void plot(int x, int y, char c)
   {
     printf("\x1b\x5b%d;%dH%c", y, x, c);
   }
   pt pt1 = {20,10};
   pt pt2 = {40,30};
   pt pt3 = {0,30};
   void line(pt a, pt b)
   {
     pt change = {b.x - a.x, b.y - a.y};
     int ctx = change.x > 0 ? change.x : -change.x;
     int cty = change.y > 0 ? change.y : -change.y;
     int ct = ctx > cty ? ctx : cty;
     for (int t = 0; t <= ct; ++ t) {
       plot(a.x + change.x * t / ct, a.y + change.y * t / ct, '*');
     }
   }
   int main()
   {
     line(pt1, pt2);
     line(pt2, pt3);
     line(pt3, pt1);
   }

References

   1. mailto:gmkarl@gmail.com