To determine the number of partitions using one-dimensional equivalence partitioning, we need to consider each aspect of the ID requirement individually.
* Length of the ID:
* Valid partitions: 5 to 10 characters (1 partition)
* Invalid partitions: Less than 5 characters, more than 10 characters (2 partitions)
* Type of characters:
* Valid partitions: Alphanumeric characters (1 partition)
* Invalid partitions: Non-alphanumeric characters (1 partition)
* Type of first character:
* Valid partitions: First character is a letter (1 partition)
* Invalid partitions: First character is not a letter (1 partition)
Adding these together, we have a total of 1 (valid length) + 2 (invalid lengths) + 1 (valid type) + 1 (invalid type) + 1 (valid first character) + 1 (invalid first character) = 7 partitions.