-4 5 setxrange
-2.1 5 setyrange

/A {-3 -1} def
/B {0 1} def

/U {-2 3} def
/u {2 -1} def
/V {4 2} def
/v {-1 2} def

quadrillage

[A B] points

20 setfontsize
setTimesItalic
   (A) A urtext
   (B) B urtext

[U V] points
U dupp u addv (->) line
V dupp v addv (->) line