The practical aspects of using a layered software approach for small-embedded systems

For international products such as pagers, it is difficult to develop a sin gle product which can support different languages (e.g., Indian scripts and Chinese scripts) and receive protocols. Usually for different pagers, the same core software is maintained with appropriate changes made to support a different language or protocol. A layered approach of software development would make the software reuse easier and speed up code development. Howeve r, a pager has severe limitations in CPU speed, RAM and ROM which makes the layered software development not so practical. NEC Australia and NEC Japan have managed to develop the software for an Indian pager using a layered a pproach with trade-offs made for speed, RAM and ROM size. The project has b een completed successfully with no performance degradation to the performan ce of the pager. Due to the layered approach taken, the next pager develope d (a Chinese pager) using this software as a base was completed in record t ime and with minimal bugs. This paper will describe the architecture of the software and the trade-offs taken in using a layered approach for a small- embedded system. A case study will be presented on the steps in reusing the software for changing the display language.