Accelograms

Hi

    When I was going through few research articles related to earthquake analysis, they say: A compuetr code was developed where in which the eartquake input will be in either accelerogram or a displacement time history, digitized in in the appropriate format. What does it mean? Doest it mean that in studying simulation of seismic analysis  we need to load that code as input? How to get an idea about that codes? Where to get? How to use?

   Please help.........

Thanks in advance........