Instruction set classified by Data types
  Addressing
  Boolean
  Numbers
  Characters

Address
  Address
    Data represents a memory address.
    Addresses are unsigned.
      Some systems have a smaller data path than address path.
        Requires multiple reads
    Other systems have a data path wider than address path.
      Original IBM 360 had 32 bit registers but only a 24 bit address.
      (4 Meg). Upper 4 bits of register ignored.

Boolean
  Boolean
    Each bit of memory unit represents a separate piece of data.
    Instruction able to address individual bit for setting or testing.
      Either directly or with help of a mask.

Numbers
  Numbers
    Integers - signed and unsigned - requires zero, carry, overflow.
    Floating point
      Some cpus do not support fp numbers at hardware level.
    Binary coded decimal - represents 0-9
      Easy for non-programmers to read data dumps.
      More complex (slower) execution by cpu.

Characters
  Characters
    ASCII - seven bit values English characters
      a-z,A-Z, 0- 9, punctuation.
      various tab and positioning for display and printing.
      8th bit used for parity or alternative character set (graphics).
    EBCDIC (extended binary coded decimal )
      8 bit character set.
         IBM's character set
      Uni-code
        16 bit character set
        Standardized multi-language character set