HP C A.06.05 Reference Manual

What is HP C?
ANSI Mode
Chapter 12
ANSI Mode
Unless you are writing code that must be recompiled on a system where ANSI C is not
available, it is recommended that you use the ANSI mode of compilation for your new
development. It is also recommended that you use ANSI mode to recompile existing programs
after making any necessary changes.
Because an ANSI-conforming compiler is required to do more thorough error detection and
reporting than has been traditional among C compilers in the past, you may find that your
productivity will be enhanced because more errors will be caught at compile time. This may be
especially true if you use function prototypes.
If you do not specify the mode of compilation, beginning with the HP-UX 10.30 operating
system release, it defaults to -Ae.