E..5

z=[x^2-y^2 for x in -1:0.01:1, y in -1:0.01:1]
contour(z)
contour(z,fill=true)

wireframe(z)

a=-1; b=1; nx=100; x=range(a,stop=b,length=nx+1)
c=-1; d=1; ny=100; y=range(c,stop=d,length=ny+1)
f(x,y)=x^2-y^2

contour(x,y,f)

surface(x,y,f)

plot(x,y,f, st = [:surface, :contourf], layout=@layout [a{0.5w} b])