This is for C programing :

complex(x,y) = x*{1,0}+y*{0,1}

mandel(x,y,z,n) = (abs(z)>2.0 || n>=100) ? n :

mandel(x,y,z*z+complex(x,y),n+1)

set xrange [-1.5:0.5]

set yrange [-1:1]

set logscale z

set isosample 50

set hidden3d

set contour

splot man

del(x,y,{0,0},0) notitle

a. Draw a graph of sin(x3) for