Although they appear to specify details about data structures, MIB standards do not dictate the implementation. Instead, MIB definitions provide a uniform, virtual interface that managers use to access data; an agent must translate between the virtual items in a MIB and the internal implementation.
In programming language terms, we think of the IP address table as a one-dimensional array, where each element of the array consists of a structure(record) that contains five items: an IP address, the integer index of an interface corresponding to the entry, an IP subnet amsk, an IP broadcast address, and an integer that specifies the maximum datagram size that the router will reassemble. Of course, it is unlikely that a router has such an array in memory. The router may keep the information in many variables or may need to follow pointers to find it. However, the MIB provides a name for the array as if it existed, and allows network management software on individual routers to map table references into appropriate internal variables.