Error checking with pointer variables

The use of pointer variables in a programming language often results in a difficult class of errors to detect. Pointers may point to storage that no longer is allocated, or storage may be allocated as one data type and accessed as another. This report describes the implementation of pointers in the PLUM PL/1 compiler such that all error conditions are detected. In addition, preliminary tests with PLUM seem to indicate that the total checking of pointers is not as expensive an operation as it first appears.