This research [26], using simulation, showed that by using multi-levels of superimposed codes, substantial improvements in retrieval might be achieved, compared to the method proposed by Roberts. This was particularly true for large information files, of the order of 1 million records or more. The preliminary research above was so encouraging that the author continued with the research. The additional research is the basis of this thesis. 1.2 What are Superimposed Codes. Superimposed codes are

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... sed as an aid in retrieving information. They can be used in place of indexes, trees, or the hashed organization. In some instances, superimposed codes outperform the other methods. Section 1 Mooers [20] used edged-notched cards back in 1955. Edged-notched cards are a mechanical version of superimposed codes. The cards, which had information written on them, represented the primary records. The Section 1 superimposed coding method itself, and section 8 suggests ways in which other retrieval method could be combined with the superimposed coding method.