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Excelsior Eases Migration of Aerodata's Core Software To a New Platform

Using a custom version of Excelsior's Native XDS-PPC Modula-2 compiler, Aerodata Flugmesstechnik was able to rapidly migrate its MODAMS core to the new hardware platform with minimal changes. "We needed it to run on the more powerful PowerPC CPU, but our legacy Modula-2 compiler did not support that processor and was no longer maintained by the vendor," said Ludger Mastall, Manager Software Development for Aerodata Flugmesstechnik. "Without Excelsior's help, we would have to rewrite everything in C by hand, which would greatly increase costs and possibly compromise delivery times in the big contract we were recently awarded by the Japanese Aviation Bureau".

The system engineering company Aerodata Flugmesstechnik GmbH, founded 1985, is the kernel of the Aerodata Group - the world leader in manufacturing airborne equipment for the safety inspection of air navigation infrastructure and the largest corporate supplier of associated flight inspection services. As a technology oriented aviation system company and GPS applications pioneer, the group supplies products and services for air traffic control as well as a wide variety of airborne special mission solutions.

The core of Aerodata's Flight Inspection System is the software package known as MODAMS (Modular Online Data Acquisition Monitoring System). MODAMS performs parallel computer processes in real time: operator dialogue, monitoring processes, data processing and data storage. The system displays electronic maps in the aircraft cockpit or at the operator's console which enhances information exchange between the flight crew, pilots, and flight inspectors. This, in turn, further enhances the efficient operation of the system.

MODAMS was originally designed to run under DEC RT-11 on PDP-11 based systems and then ported to Microware's OS-9 for Motorola 680x0 series CPU. For the new generation of Flight Inspection Systems, in which real time data acquisition and navigation calculation will be done on the same computer, Aerodata had selected the more powerful PowerPC 8240 CPU. The problem was that the MCS Modula-2 compiler, which Aerodata had been using for MODAMS development, did not support PowerPC. "We had about half a million lines of Modula-2 code and almost no means to get them running on the new platform," said Mastall, "except by manually rewriting everything in C or C++".

Excelsior had made an offer to Aerodata to create a custom Modula-2 compiler for their new target. Excelsior's proprietary XDS compiler construction framework, among other components, contains a Modula-2 front-end and PowerPC code generator. It allowed Excelsior to quickly create a reasonably priced optimizing Windows NT-hosted Modula-2 cross-compiler targeting OS-9 for PowerPC. It was named Native XDS-PPC after its counterpart Native XDS-x86, available on the market since 1996.

Excelsior XDS Modula-2 compilers comply to the ISO 10514 International Standard, whereas MCS belongs to the pre-ISO generation and also has its specific language extensions and library modules. This could potentially lead to an enormous amount of source code changes during migration thus greatly reducing the reliability of MODAMS. To help Aerodata solve this problem, Excelsior had customized the compiler and the run-time library, making them more compatible with MCS. As a result, most of Aerodata's source code could be passed through the XDS compiler without changes, and only a few low-level CPU-dependent modules needed complete rewriting. "We have managed to find the right balance between the amount of the XDS system customizations and the amount of required changes in our source code, thus minimizing costs and delivery time", said Mastall.

After the approach proposed by Excelsior has proved its viability, Aerodata immediately purchased two additional licenses for the Native XDS-PPC compiler. "Now we know whom to contact first, have our programmers a need for a custom development tool," said Dr. Manfred Haverland, Managing Director for Aerodata Flugmesstechnik.

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