at the beginning of the twenty-first century, many firms that used only two digits to represent the year were faced with a major problem called the

Y2K problem

Explanation:

Y2K problem is short for Year 2000 problem or also called millennium bug, was a computer program problem because the coding in the computer systems till 1990's was such that they save the years in two digits instead of four to save space. For example, the year 1998 was saved as '98'. It created an environment of fear among many government offices and data processing companies that the computers would stop working from mid night of 1 January 2000.

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