6. An apparatus for changing a format of a file, comprising: means for inputting a first element having a first representation; means for converting said first element of the first representation to a second representation; means for inputting a subsequent element of the first representation; means for determining if a second representation of the subsequent element includes a portion which is found in the second representation of said first element; means for converting said subsequent element to the second representation including said portion when said means for determining determines that said portion is not found in the second representation of said first element; and means for converting said subsequent element to the second representation without said portion when said means for determining determines that said portion is found in the second representation of said first element.
6. An apparatus for changing a format of a file, comprising: means for inputting a first element having a first representation; means for converting said first element of the first representation to a second representation; means for inputting a subsequent element of the first representation; means for determining if a second representation of the subsequent element includes a portion which is found in the second representation of said first element; means for converting said subsequent element to the second representation including said portion when said means for determining determines that said portion is not found in the second representation of said first element; and means for converting said subsequent element to the second representation without said portion when said means for determining determines that said portion is found in the second representation of said first element. 8. An apparatus according to claim 6, wherein data structures having at least two different fields are used to store conversion information used by each of said converting means to convert corresponding elements of the first representation including said first element and said subsequent element to said second representation, one of said at least two different fields being used to store conversion information of the element which is always required to appear in the second representation of the corresponding element and another of said at least two different fields being used to store said portion of the corresponding element.