ion, for example. The presentation layer at the other end decodes the compressed data to the required representation at the destination. The presentation layer helps both computers understand the meaning of the received bit stream the same way. Different computers have different internal representations of data. All IBM mainframes use extended binary coded decimal interchange code (EBCDIC) 8-bit codes as character code; whereas practically all others use ASCII 7- or 8-bit options. The Intel chips number their bytes from right to left, whereas Motorola chips number theirs from left to right. Because com- puter manufacturers rarely change these conventions, it is unlikely that any universal standards for internal data representation will ever be adopted. One solution to ensure compatibility is to define a presentation layer standard for the "network representation" of data and any computer may communicate with another if each of them converts its internal representa- tion to this standardized network format. When this is implemented into each computer, all can communicate with all others and there is no need for data conversion between each pair of computers. Other tasks for the presen- tation layer are data compression and encryption. Some examples of presentation layer protocols are IS 8824-1 through -4, which are standards for the representation of data structures, and Abstract Syntax Notation 1 (ASN.1 abstract because it is just a representation). ASN.1 descriptions are quite similar to any high-level programming lan- guage and include definitions of data structures such as integer and floating- point number. Another example includes IS 8825-1 and -2, which are encoding rules for ASN.1 defining how representations are encoded into a bit stream for transmission. In the TCP/IP protocol stack a separate presentation layer does not exist and its functions are integrated into the highest layer, the application layer, as shown in Figure 6.11. Data Communications 6.3.3.8 Application Layer The application layer contain