Using EDF in single-screen mode

When you use EDF with just one terminal, the EDF inputs and outputs are interleaved with those from the transaction.

This sounds complicated, but works quite easily in practice. The only noticeable peculiarity is that when a SEND command is followed by a RECEIVE command, the display sent by the SEND command appears twice: once when the SEND is executed, and again when the RECEIVE is executed. It is not necessary to respond to the first display, but if you do, EDF preserves anything that was entered from the first display to the second.

You can start EDF in two ways:
  • Entering transaction code CEDF from a cleared screen
  • Pressing the appropriate function key (if one has been defined for EDF)
Next, you start the transaction to be tested by completing the following steps:
  1. Press the CLEAR key to clear the screen.
  2. Enter the transaction code of the transaction you want to test.
When both EDF and the user transaction are sharing the same terminal, EDF restores the user transaction display at the following times:
  • When the transaction requires input from the operator
  • When you change the transaction display
  • At the end of the transaction
  • When you suppress the EDF displays
  • When you request USER DISPLAY
To enable restoration, user displays are remembered at the following times:
  1. At the start of task, before the first EDF screen for the task is displayed
  2. Before the next EDF screen is displayed, if the user display has been changed
  3. On leaving SCREEN SUPPRESS mode

If you use CEDF with an application program that has been translated with option NOEDF, or one that has NO specified for CEDF in its resource definition, EDF cannot ascertain when the display is changed by that application program. Therefore EDF cannot save a copy of that display for later use. The next EDF display overwrites any display sent by the application program and cannot be restored.

Similarly, CEDF cannot restore the current display when it is about to be changed by the application, or when the transaction requires input from the operator. Therefore an output command to the principal facility from the application program might result in random background information from a previous EDF display appearing on the screen.

An input command can be executed against the previous EDF display, rather than a display from the application program, or, if it is the first receive in the transaction, it might require explicit input from the CEDF panel instead of being satisfied by the contents of the initial TIOA.

These considerations apply to any screen I/O operation performed by the application program.

When EDF restores the transaction display, it does not sound the alarm or affect the keyboard in the same way as the user transaction. The effect of the user transaction options is seen when the SEND command is processed, but not when the screen is restored. When you have NOEDF specified in single-screen mode, take care that your program does not send and receive data because you will not see it.

When EDF restores the transaction display on a device that uses color, programmed symbols, or extended highlighting, these attributes are no longer present and the display is monochrome without the programmed symbols or extended highlighting. Also, if the inbound reply mode in the application program is set to character to enable the attribute-setting keys, EDF resets this mode, causing these keys to be disabled. If these changes prevent your transaction from executing properly, test in a dual-screen mode.

If you end your EDF session part way through the transaction, EDF restores the screen with the keyboard locked if the most recent RECEIVE command has not been followed by a SEND command; otherwise, the keyboard is unlocked.

Pseudoconversational programs

EDF makes a special provision for testing pseudoconversational transactions from a single terminal. If the terminal came out of EDF mode between the several tasks that make up a pseudoconversational transaction, it would be very hard to do any debugging after the first task. So, when a task terminates, EDF asks the operator whether EDF mode is to continue to the next task. If you are debugging a pseudoconversational task, press Enter to accept the default, which is Yes. If you have finished, reply No.