What  kind of input files do you wnat to build? VASP reads out four input files, the INCAR, POSCAR, KPOINTS and POTCAR files.

The POTCAR contains the pseudopotentials for every atom in your calculation, and these files are given by the VASP team with the code.

The KPOINTS file is usually a few lines long if you are generating the k-point grid "automatically", if for some special reason you need to sample the reciprocal space in an irregular way I would recommend writing your own program in whichever programming language you prefer.

For generating the positions of the atoms in the POSCAR file I also suggest writing your own code, but if you already have coordinate files in some other format, or you want to visualize your system, there are several translators:

vasp to cif and cif to vasp (https://www.nsc.liu.se/~pla/vasptools/)

vasp to xcrysden (http://theory.chm.tu-dresden.de/~jk/software.html)

Some codes such as VESTA can directly read POSCAR or CONTCAR (equivalent to POSCAR) files.

The INCAR file contains all the rest of the information for the calculation, including the smearing, the minimization algorithm, if you are doing a self-consistent calculation or not, relaxing atomic positions or not...

Check the resources listed in the official VASP site (https://www.vasp.at/index.php/resources) and, for many interesting input and output manipulation tools, http://theory.cm.utexas.edu/vtsttools/

http://theory.cm.utexas.edu/vtsttools/

https://www.vasp.at/index.php/resources)

For building POSCARs you want to use VESTA.

http://jp-minerals.org/vesta/en/

Hugo,Régis and Lane thank you very much for your help. I will use that and tell you later.

If you can express your system logically, check out python-ase package. It's a python module which can write POSCARs from your defined systems. It even has some basic structues. See the gist for example code to create a bunch of POSCAR with different lattice parameters ratios

https://wiki.fysik.dtu.dk/ase/index.html

https://gist.github.com/cra/928b7594d26cba771169

Thank you Igor very much for your help, i will do that and for any problem i will let you know.

As for me, usually I'm writing my own code and to visualize and check my system use Visual Molecular Dynamics (VMD).

http://www.ks.uiuc.edu/Development/Download/download.cgi?PackageName=VMD

Also you can use vaspkit it is a very nice program:

http://vaspkit.sourceforge.net