If unwanted words have to be deleted and new words inserted one at a time, there is a need for a special register to distinguish between active and inactive words. This register, sometimes called a tag register, would have as many bits as there are words in the memory. For every active word stored in memory, the corresponding bit in the tag register is set to 1. A word is deleted from memory by clearing its tag bit to 0. Words are stored in memory by scanning the tag register until the first 0 bit is encountered. This gives the first available inactive word and a position for writing a new word. After the new word is stored in memory it is made active by setting its tag bit to 1. An unwanted word when deleted from memory can be cleared to all 0's if this value is used to specify an empty location. Moreover, the words that have a tag bit of 0 must be masked(together with the K bits) with the argument word so that only active words are compared.