(1) A data item used for storing numbers or number representations in a manner that permits these numbers to be increased or decreased by the value of another number or to be set to an arbitrary value.
(2) A register or storage location used to accumulate the number of occurrences of an event.
(3) A representation of information that is cumulative up until the sample is taken. The counter counts values that increase, such as the number of deadlocks. Counters are reset when an instance or a database is stopped and restarted. See also gauge.
(4) A binary string that is used by some block cipher modes in an exclusive-OR (XOR) operation. It is incremented and then applied in the encryption or decryption of each block of data. For a given key, a counter should never be repeated.
(5) A specialized metric used to keep track of the number of occurrences of a specific situation or event. For example, you can use a counter to track the number of times that a task is started within a process, where that task is contained in a loop.