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  So far, we've discussed the CPU, the support chips, and the bus, but
  we've only touched on memory. We've saved our discussion of memory for
  the end of this chapter because memory chips, unlike the other chips
  we've discussed, don't control or direct the flow of information through
  a computer system; they merely store information until it is needed.

  The number and storage capacity of memory chips that exist inside the
  computer determine the amount of memory we can use for programs and
  data. Although this may vary from one computer to another, all PCs and
  PS/2s come with at least 40 KB of read-only memory (ROM)--with space for
  more--and between 64 KB and 2 MB of random-access memory (RAM). Both ROM
  and RAM capacities can be augmented by installing additional memory
  chips in empty sockets on the motherboard as well as by installing a
  memory adapter in one of the system expansion slots. But this is only
  the physical view of memory. A program sees memory not as a set of
  individual chips, but as a set of thousands or millions of 8-bit
  (1-byte) storage cells, each with a unique address.

  Programmers must also think of memory in this way--not in terms of how
  much physical memory there is, but in terms of how much addressable
  memory there is. The 8088 and 8086 can address up to 1 MB (1024 KB, or
  exactly 1,048,576 bytes) of memory. In other words, that's the maximum
  number of addresses, and therefore the maximum number of individual
  bytes of information, the processors can refer to. Memory addressing is
  discussed in more detail in Chapter 2.