The presentation layer is the lowest layer at which application programmers consider data structure and presentation, instead of simply sending data in the form of datagrams or packets between hosts. This layer deals with issues of string representation - whether they use the Pascal method (an integer length field followed by the specified amount of bytes) or the C/C++ method (null-terminated strings, e.g. codice_1). The idea is that the application layer should be able to point at the data to be moved, and the presentation layer will translate this to commands able to be understood by other applications and processes.