parabolic reflector hpbw

hi,are there any program that u give him the band and the gain,calculate the dimension and the directivity,and other parameters
regards

Check these links:
http://www.csgnetwork.com/antennaparaboliceffcalc.html
http://www.csgnetwork.com/antennaparaboliccalc.html
http://www.cgi-bin.com/cgi-bin/jump2.cgi?ID=151

In the usual case that λ>> Diameter and for λ>>rms mirror accuracy, you don't need any sophisticated software. Just apply:

G= η 4 pi A /λ2

pi=3.1415...
A=Aperture area
η= efficency (0...1), but acceptable values for a well builted antenna are:
0.5<η<0.6 for Cassegrain or Gregorian antennas
0.4<η<0.5 for prime focus illuminated antennas
η will rise up to around 0.8 for properly shaped dual reflector.

Antennas with f/D in the 0.5...0.6 will have efficiency just a little higher than antennas with f/D in the 0.3...0.4 range.

Efficency will depend mostly on feed technology

The HPBW (Half power beam width) ≈ 80 λ/D [°deg]
D=Aperture Diameter

Ref: Jasik and Kraus

A sophisticated software is needed if you want calculate accurately η and or you want calculate the pattern.
The workhorse of commercial one is the very expensive GRASP, available free of charge in the student edition.
An old DOS fashioned, fully funtional is the REF.FOR available (i think free) from the author, now retired, Cayrle Sletten (find email on Google).