plP_checkdriverinit: Checks to see if any
      of the specified drivers have been initializedplP_getinitdriverlist: Get the initialized-driver
      listplabort: Error abortplexit: Error exitplgfile: Get output file handleplsabort: Set abort handlerplsexit: Set exit handlerplsfile: Set output file handlepltr0: Identity transformation for grid to world
mappingpltr1: Linear interpolation for grid to world
mapping using singly dimensioned coord arrayspltr2: Linear interpolation for grid to world
      mapping using doubly dimensioned coord arrays (column
      dominant, as per normal C 2d arrays)The purpose of this chapter is to document the API for every C function in PLplot (other than language bindings) that is not part of the common API that has already been documented in Chapter 16.
This chapter is a work that is just starting. There are many C functions in the code base that are not part of the common API, and we haven't even gotten to the point of listing them all. What gets documented here now is whatever C-explicit code we are trying to understand at the time.
plP_checkdriverinit: Checks to see if any
      of the specified drivers have been initialized
 Checks to see if any of the specified drivers have been
     initialized. Function tests a space-delimited list of driver names to
     see how many of the given drivers have been initialized, and how often.
     The return code of the function is: 0 if no matching
     drivers were found to have been initialized; -1 if
     an error occurred allocating the internal buffer; or, a positive number
     indicating the number of streams encountered that belong to drivers on
     the provided list. This function invokes plP_getinitdriverlist
     internally to get a complete list of drivers that have been initialized
     in order to compare with the driver names specified in the argument list
     to plP_checkdriverinit.
     
| 
 |