A method for increasing the capabilities of an object program of a digital data processing system having a coded character set, with each character having a given attribute, by providing each of a selected subset, or subsets, of said characters with a second attribute. Which attribute of a given character of such a subset is its relevant attribute is determined by such a character being the operand of a limited number of operation codes of the computer system capable of properly acting on the second attribute of the character of such a selected subset. The data entry routine of such a program is modified to require data represented by the second attributes of the selected subsets and to convert such data into a character of such a subset. For each operation code capable of properly acting on the second attribute of a character of a selected subset of said characters, a subroutine is created to check each operand acted upon by the operation code for the presence of character of a selected subset and to convert such an operand into a format upon with the desired operation can be executed. Each data output operation of an object program capable of outputting the second attribute of such a character is provided with the means to output where appropriate a graphic character, or characters, defining such a second attribute.
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