Values
Programming languages allow several
types of values: numeric, strings of
letters, Boolean
numbers:  1  0  -433  6.022e+23 .01
not numbers:  1,000   106  5%   7±2
strings:  "abc" 'efg' " "  "B&B's"  ""
not strings:  '   '<tab>'  "a '  "\"
Boolean:  true   false
not Boolean:   T   F   yes   no