COBOL Manual for TNS and TNS/R Programs

Calling Other Programs and Routines

HP COBOL Manual for TNS and TNS/R Programs—522555-006

23-20

TNS Addressing Modes

TNS HP COBOL programs use standard (16-bit) addressing for all items in the File

Section, all items in the Working-Storage Section, and items in the Linkage Section for

which standard access mode is specified. HP COBOL programs use extended (32-bit)

addressing for all items in the Extended-Storage Section and all items in the Linkage

Section for which the standard access mode is not specified. Programs written in

languages other than COBOL use both 16-bit and 32-bit addressing, with certain data

structures always using 32-bit addressing.

When a formal reference parameter (in the called routine) is 16-bit-addressed, the

corresponding actual parameter (in the calling routine) can be any HP COBOL data

item except a special register or an item declared in the Linkage Section or Extended-

Storage Section.

When a formal reference parameter (in the called routine) is 32-bit-addressed, the

corresponding actual parameter (in the calling routine) can be any HP COBOL data

item except a special register.

When an HP COBOL program passes a 32-bit-addressed parameter to a routine that

expects a 16-bit-addressed parameter, the COBOL85 compiler performs the necessary

conversion. The passed data item must begin in the leftmost byte of a word. If the data

item begins (or can begin) in a byte other than the leftmost byte, the compiler delivers

a warning, and it is your responsibility to verify that the addressing is correct.

In a called routine, the code that handles actual parameters from the calling routine is

generated according to the addressing mode that the called routine specifies for the

formal parameters. This code can include both instructions that use 16-bit addressing

and instructions that use 32-bit addressing. Instructions that use 16-bit addressing

execute faster, but cannot address items in extended memory.

Native Addressing Modes

Native programs use 32-bit addressing for all data items. Many HP COBOL data items

are byte-addressed. Some data items in other languages are 2-byte addressed. When

you pass a byte-addressed item to a routine that expects a 2-byte-addressed

parameter, the data item must be aligned on a 2-byte boundary; otherwise, problems

can arise, because the called routine is expecting an aligned parameter.

Special registers are not addressable data items. If passed as parameters, they must

be passed by value.