NOTICES FOR IFS KL1 PROGRAM EXECUTION ON PDSS

IFS (ICOT Free Software) contains PDSS, which is the KL1 execution environment running on UNIX, but the role of PDSS is now replaced by KLIC, another KL1 implementation on UNIX also distributed as IFS and much more efficient. PDSS will not be maintained well in future. Users are recommended to use KLIC instead.

PDSS enables the execution of KL1 programs on UNIX-based computer systems. However, almost all Kl1 programs distributed as IFS are supposed to be able to use PIMOS as their execution environment; PIMOS is the operating system for Multi-PSI and PIM. It must be noted that PDSS provides a different execution environment from that provided by PIMOS.

PDSS is different from PIMOS in the following points: the specification of the KL1 language, the specification of I/O, some other functionalities, execution speed, and the size of memory that can be used. Therefore, KL1 programs which are written to execute on PIMOS may or may not be executed on PDSS without some modification. Since large-scale KL1 programs that are distributed as IFS intensively use PIMOS functions, porting them to PDSS is fairly difficult.

Porting KL1 programs to PDSS may require some modification at the source code level --- the amount of modification actually depends on the contents and the sizes of KL1 programs. Sometimes just a fragment of a KL1 program may be executable on PDSS. There are several important issues to port KL1 programs from PIMOS to PDSS.

1. PDSS does not support several of the built-in predicates that have been implemented recently, such as string and bignum operations. On PDSS, this should be realized using a KL1 library.
2. There are several differences in the specification of macros. For instance, user defined macros are not usable on PDSS.
3. Basically, PIMOS system calls cannot be used on PDSS. Furthermore, the specification of I/O is different as well.
4. The specification of character strings is different.
5. On PDSS, if a predicate has too many arguments, register-shortage errors occur.