# Data types used in these manuals

The parameters passed to the Photo>Graphics PRO functions and procedures are expected to be of the correct data types. If they are not, there is an error.

Since REXX has a very loose idea of what types are, I will describe the four data types that will be mentioned in this document:

boolean
  A boolean may be either 1 or 0, representing true and false respectively. No other values are allowed.
numeric
  A numeric value may be any number between -70000000 and 70000000.
string
  A string is just a REXX string, i.e. any value. Note: if the string contains a null character (x2c(0)) that may cause everything following that character to be ignored.
handle
  A handle is a way of referencing Photo>Graphics PRO objects and resources. A handle is always created by one of the Cw functions and is only ever referred to by them. The only exception to this is the null handle, which is used to indicate failure or completion. The value 0 may sometimes be used in place of a handle to represent the null handle. However, it is not guaranteed that a handle that is not 0 is not the null handle. Use CwIsHandleValid to check.

(A handle is actually a string of the form "hnd:X" where X is a number. However, this may be changed in later versions so don't depend on it. Pretend you don't know what a handle looks like.)

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