HP 300s Scientific Calculator - Manual (Page 46)

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Factorial (!)
This function obtains the factorials of a value that is zero or a
positive integer.
Example: (5 + 3)! = 40320

       (x!) 
Absolute Value Calculation (Abs)
When you are performing a real number calculation, this
function simply obtains the absolute value.
Example: Abs(2 - 7) = 5

       
Random Number (Ran#)
This function generates a 3 digit pseudo random number that
is less than 1.

   
  (Ran#) 


Generate three 3-digit random numbers. The random 3 digit
decimal values are converted to 3 digit integer values by
multiplying by 1000.
Note that values shown here are examples only. Values
actually generated by your calculator will be different.