1. Field of the Invention.
This invention relates to systems and methods for determining the order of sets of data records based upon the value of the keyfields associated with each record.
Information to be processed by a computer apparatus may be stored in computer memory or on some external storage device such as a magnetic tape or magnetic disk. The information is typically blocked or grouped into units, commonly referred to as "records," each of which contains similar information. For example, a business may compile a record of each of its employees, customers and/or products. Each record is comprised of different pieces of information, commonly referred to as "fields." For example, an employee record may include fields such as employee name, age, address, and social security number. Each field contains one or more alphanumeric characters. Each alphanumeric character is typically coded in binary form.
It is frequently desirable to determine of the records based upon the value of a selected field, commonly referred to as the "keyfield." For example, it may be desirable to determine the order of employee records alphabetically by employee name. This is typically accomplished by repeated comparisons of the coded binary keyfield values under control of a computer program to form an ordered sequence of records.
2. Description of the Prior Art.
Ordering of information is one of the most extensively used applications performed by today's general purpose computers. To accomplish this task, systems for ordering of data records based on the coded binary value of the keyfields associated with each record are well known. However, prior systems have several disadvantages associated with them.
For example, some systems operate at relatively slow speeds due to the fact that for each record, each and every bit comprising the keyfield of that record is processed in series. Other systems also function at relatively slow speeds because the keyfield of a record is repeatedly directly compared with the keyfields of many or all other records. Some systems overcome this speed limitation by employing multiple duplicative stages of comparison hardware and/or relatively large amounts of local storage. The system disclosed in U.S. patent application Ser. No. 410,414 filed on Aug. 23, 1982, now U.S. Pat. No. 4,611,310, to the same inventor as the present application overcomes the speed limitation but requires a relatively large matrix memory for holding the intermediate results of the ordering process.
Accordingly, it is an object of the present invention to provide a general system and method for ordering a plurality of records based on the coded binary value of the keyfields associated with each record, which overcomes the above disadvantages.