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Hollerith constants, named in honor of Herman Hollerith, were used in early FORTRAN programs to allow manipulation of character data. Early FORTRAN had no CHARACTER data type, only numeric types. In order to perform character manipulation, characters needed to be placed into numeric variables via Hollerith constants. For example the constant 3HABC specified a three-character string 'ABC'. These constants were ''typeless'', so that there were no type conversion issues. If the constant specified fewer characters than was possible to hold in a data item, the characters were then stored in the item ''left-justified'' and ''blank-filled''.== Mechanics == By the FORTRAN 66 Standard, Hollerith syntax was allowed in the following uses: * As constants in DATA statements* As constant actual arguments in subroutine CALL statements* As edit descriptors in FORMAT statementsPortability was problematic with Hollerith constants. First, word sizes varied on different computer systems, so the number of characters that could be placed in each data item likewise varied. Implementations varied from as few as two to as many as ten characters per word. Second, it was difficult to manipulate individual characters within a word in a portable fashion. This led to a great deal of ''shifting and masking'' code using non-standard, vendor-specific, features. The fact that character sets varied between machines also complicated the issue. Some authors were of the opinion that for best portability, only a single character should be used per data item. However considering the small memory sizes of machines of the day, this technique was considered extremely wasteful. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hollerith constant」の詳細全文を読む スポンサード リンク
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