Rmode and Amode: options at the time of compilation

mf_me · New User Joined: 18 Jul 2005 Posts: 3

what are these options at the time of compilation. I know the values these 2 parameters can have is 24,31 or ANY , that it has something to do with above or below the 16 Mb line.
but finally i am all confused
can someone explain in simple way

brain_s390 · New User Joined: 06 May 2005 Posts: 58 Location: Mumbai

Hi,

When you run your COBOL programs, the programs and the data that they use reside in virtual storage. Storage that you use with COBOL can be either below the 16-MB line or above the 16-MB line but below the 2-GB limit. Two modes of addressing are available to address this storage: 24-bit and 31-bit.

Addressing mode (AMODE) is the attribute that tells which hardware addressing mode is supported by your program: 24-bit addressing, 31-bit addressing, or either 24-bit or 31-bit addressing.

Residency mode (RMODE) is the attribute of a program load module that identifies where in virtual storage the program will reside: below the 16-MB line, or either below or above.

Sasi Kiran Patha · Posted: Thu Oct 04, 2007 10:23 am

hi,

The definitions seem fine.

I would prefer internals or basics of this concept in terms of OS concepts and Computer Architecture concept.

Whenever i come accross these definitions things appear vague because of missing the essential basics or internals.

Probably an example with numbers consisting of bits and bytes and programming situations would clarify me.

murmohk1 · Posted: Thu Oct 04, 2007 10:29 am

Sasi,

dick scherrer · Posted: Thu Oct 04, 2007 12:13 pm

Hello,

Another way to think of this is that with 24 bits the largest number that can be represented is 16 meg. If you only have 24 bits, you cannot address beyond 16 meg, hence the restriction.

It is also the source of the "16 meg line".

Unless you get into other than application programming, you will not directly be concerned addressability issues. Your use of amode and rmode will not be a program by program decision - these will most likely be set system or application wide.