The 7489 TTL Ram Device:

The 7489 TTL Ram package has 64 memory cells, each cell is capable of holding a single bit of data.  The cells are organised into locations, and each location is capable of holding a 4-bit word.  Thus the 7489 is capable of storing 4-sixteen 4-bit words, i.e. four memory cells are used at each location.  Figure 8 shows the memory organisation of the 7489 static RAM.

7489 RAM Device

Each location is identified by a unique 4-bit address so that data can only be written or read from that location.  The number of words stored in the memory determines the length of the address word.  I.E. 16 = 2⁴.