Types of Access

The MTT system supports 2 types of access:-

Link Access

the system provides a pointer to the titles bank in the special ZEBRA xCONS (ICONS/RCONS) memory.

COMMON Block Access

the system provides pointers as for LINK Access but also copies all user data to a user designated COMMON.

Link Access is the preferred form because:-

• It avoids duplicating the data in a bank and a COMMON.

• It avoids the possibility of COMMON block conflict when new software requires 2 or more existing titles banks.

• A bank permits a more flexible data structure e.g. variable length lists, than does a COMMON.

However it is recognised that some people feel far more at home with a COMMON block, hence the provision!

In either case, someone requiring access to a titles bank must first create an 8 word array and store it in a COMMON. A recommended naming convention for the array is LAxxxx (Link Access) where xxxx is the bank name. The COMMON may be shared by any number of routines and may hold any number of LAxxxx arrays. The LAxxxx contains:-

LAxxxx(1..5) 		  Reserved words - DON'T TOUCH!.  


Don't even preset to zero!. 


LAxxxx(6) 		  Link to bank = Lxxxx.  


ICONS(Lxxxx) is the ZEBRA status word.  


LAxxxx(7) 		  Link to user data = LDxxxx.  


ICONS/RCONS(LDxxxx+1) is the first word of user data. 


LAxxxx(8) 		  The number of words following to hold user data ($\geq$ 0)

So, for example, if setting up an LAxxxx array for the titles bank name RFXM and number 1, a possible definition might be:-

 
      COMMON/MYCOMM/ LARFXM(8)
      INTEGER        LRFXM,LDRFXM
      EQUIVALENCE    (LARFXM(6),LRFXM),  (LARFXM(7),LDRFXM)

In the discusion that follows each form of access is decribed for a fictitious RFXM 1 bank. The assumed format of the user data is:-

1 		 I 		  The number of media following = n. 


2 		 R 		  The refractive index of the first medium.


3 		 R 		  The refractive index of the second medium.



. 		 . 		 .

. 		 . 		 .

. 		 . 		 .




1+n 		 R 		  The refractive index of the nth medium.




Where:- 




I 		  Integer 


R 		  Floating Point