A very useful feature of PARADYME is the ability to specify 'nested displays'. This means that the user can display a field off a CHECK file. They can then take this display as the key to another file and display data off this second CHECKed file. They can then take this displayed data as the key to a third file and display data off this file and so on.

There is no theoretical limit to the number of times the user can repeat this process. The only condition that must be followed is that all displayed data must be related to the previous entry. This means that the user can not jump back to a previous definition and start displaying from there. However, they can re-specify the starting point and apply a 'NULL' conversion to it. This will result in the read taking place but no displays taking place. It is also easier if the user uses a 'V' type variable from which to start the 'nesting'.

Below is an example definition that shows off some 'nested displays'.

Prompt 1 reads in the main update record. Only the value input is displayed as a result of this definition. The next field entered is 'DATA5'. This is checked against file T3. If it is valid, the system then displays T3.DESCRIPTION and T1.KEY off the T3 file record. Furthermore, it uses T1.KEY as a key to access a record in the T1 file. It then displays T1.DESCRIPTION off this record.

Prompt 6 then respecifies the 'nested display' start. It takes the original value, now held as R.DATA and using it is a key to access a record on the T4 file. Following definitions can then specify displays off the T4 record and displays using data off the T4 file as keys.

Although this is a fairly simple technique, it is also one that may take time to fully master. This will only come with time and practice. However, once mastered, it becomes an exceptionally powerful feature of PARADYME.