Consider the Differences Between the 32-bit and 64-bit Data Models
The biggest difference between the 32-bit and the 64-bit compilation environments is the change in data-type models. The C data-type model for 32-bit applications is the ILP32 model, so named because the int and long types, and pointers, are 32-bit data types. The data-type model for 64-bit applications is the LP64 data model, so named because long and pointer types grow to 64 bits. The remaining C integer types and the floating-point types are the same in both data-type models.
