-3 6 setyrange
quadrillage
.5 setlinewidth
tracerepere
marks

/A {-4 -1} def
/B {1.5 3} def
/C {4 5} def

[A B C] points
.5 setlinewidth
A B droite

setTimesItalic
   (A) A drtext
   (B) B ultext
   (C) C ultext