tYSR20

Chapter 8: Taking a First Look at C++ Pointers 115Similarly, because pintVar is of type int*, the type of *pintVar is int:*pintVar = 10;// both sides of the assignment are// of type intThe type of the thing pointed to by pintVar is int. This is equivalent tosaying that, if houseAddress is the address of a house, the thing pointed atby houseAddress must be a house. Amazing, but true.Pointers to other types of variables are expressed the same way:double doubleVar;double* pdoubleVar = &doubleVar;*pdoubleVar = 10.0;A pointer on a Pentium class machine takes 4 bytes no matter what it pointsto. That is, an address on a Pentium is 4 bytes long, period.Matching pointer types is extremely important. Consider what might happenif the following were allowed:int n1;int* pintVar;pintVar = &n1;*pintVar = 100.0;The second assignment attempts to store the 8-byte double value 100.0 intothe 4-byte space allocated for n1. Actually, this isn’t as bad as it looks — C++is smart enough to demote the constant 100.0 to an int before making theassignment.It is possible to cast one type of variable into another:int iVar;double dVar = 10.0;iVar = (int)dVar;Similarly, it is possible to cast one pointer type into another.int* piVar;double dVar = 10.0;double* pdVar;piVar = (int*)pdVar;Consider, however, what catastrophes can arise if this type of casting aboutof pointers were to get loose. Save a variable into an area of the wrong size,and nearby variables can be wiped out. This is demonstrated graphically inthe following LayoutError program.