A new computer code, i.e., the ACAT code, has been developed to simulate atomic collisions in amorphous targets using binary collision approximation, where random targets are simulated employing the so-called cell model which is successfully used in the liquid theory. The ACAT code is used to study the backscattering and the implantation of 0.01-10 keV hydrogens on Au and on Cu. In comparing the calculated results of the ACAT code with those of the MARLOWE and TRIM codes, as a whole, an agreement between these three codes is satisfactory, and the ACAT and TRIM codes give almost the same results for energy spectra of backscattered particles and other related quantities. Using the ACAT computer code, it was found that in light ion backscattering the potential parameter as well as the inelastic energy loss parameter has an appreciable influence on the particle and energy reflection coefficients.