12  Pascal User Manual  I.D.  Numbers  Decimal notation is used for numbers, which denote either integer or  real values. Any number can be preceded by a sign  (+ or -);  unsigned  numbers  cannot be signed. No comma may appear in a number. Real  numbers are written with a decimal or scale factor or both. The letter  E  (or e) preceding the scale factor is pronounced as "times 10 to the  power." Note that if a real number contains a decimal point, at least one  digit must precede and follow the point.  Examples of unsigned numbers.  Incorrectly written numbers:  3,487,159  3.487.159  XII  3.  E10  5.E-16  five  3  03  6272844  0.6  5E-8  49.22E+08  1E10  Sequences of characters enclosed by apostrophes (single quote marks)  are called  strings.  To include an apostrophe in a string, write the  apostrophe twice.  I.E.  Character Strings $^{.6 }$ Figure I.e  Syntax diagram for  UnsignedNumber  Figure I.d  Syntax diagram for  UnsignedInteger; DigitSequence  ( __ "_I_D_igl_.t ___  DigitSequence  >+--~  DigitSequence 