Final answer:
The need to rewrite the source code for an application when moving from one POSIX-compliant system to another is generally false, as POSIX standards aim to ensure portability and reduce the necessity of complete rewrites.
Step-by-step explanation:
The question concerns whether the source code of an application that is written to work on one machine with a specific architecture and operating system would need to be rewritten to work on another machine with a different architecture and another operating system, assuming both operating systems are POSIX compliant. The statement is false. POSIX compliance ensures that applications written for one POSIX-compliant system should be largely portable to another, reducing the need for complete rewrites. However, differences in architecture or other system-specific considerations might require some parts of the code to be adapted or optimized. Managers like IBM, Microsoft, and Sun Microsystems, despite providing proprietary operating systems, all adhere to certain standards that ensure a degree of interoperability.