Re: Arrow keys + scroll keys -- MIDRANGE-L

Hmm, interesting question.

The 5250 device is a block-mode device, PCs and Unix devices are character-mode devices. I.e., the screen for a 5250 device is sent as a block for the entire screen at one time.

Also, generally speaking, only function keys and a few others (HELP, ENTER, PAGEUP/PAGEDOWN, etc.) will send anything back to the 400 - these are the things read by a program when it executes a READ of a display device.

Navigation keys only move around the current screen (block) and do not get read by an application. The cursor position is not known until some actionable key is pressed. So a cursor down will just keep going down or wrap to the top of the screen. This is all under control of the device or emulation.

In the PC world, every key press in received as struck by some application (character-based). Therefore, the developer can take any action with any key - a 'p' typed at the bottom row of a word processor could cause a PAGEUP, although I don't recommend this. ;-) Some application receives some kind of key-code for each key of a PC keyboard.

So there have been a few ways of handling scrolling (or rolling, as it's called in 5250-land):

1. In SEU you can select various ways to roll the screen, including roll a half or full page, roll to the cursor, roll a set number of lines, or roll a page less 1 line, so that you see the last row from the page you left. Of course, you have to press a ROLL key to activate this.

2. On various DSP screens (DSPPFM, DSPSPLF, etc.) a position field is used, whether absolute or relative. Enter must be pressed to move that distance.

3. In HELP screens, F10 can be used to move the line at the cursor position to the top of the screen or window. Again, an actionable key (F10) has to be pressed.

This distinction of block vs. character mode also makes the various shell terminals a little strange at first for Unix types. I speak of QShell and PASE. In Unix, e.g., if you pipe the "cat" command through the "more" filter (cat filename | more), then to move 1 line you press ENTER or SPACE (I forget which) and press the other to move a page. The "more" app is waiting on certain key presses. But from the command line of Unix you can't automatically cause scrolling. And there is no cursor (usually) in a command line screen in Unix or DOS, in the sense that there is in certain applications (DOS's QBASIC and EDIT come to mind) and certainly as it is in Windows applications, which may be what you meant by "PC" applications.

Hope this made a little sense - i wax too verbose, but the topic struck my fancy for a moment!

Vern

At 12:55 PM 1/19/2004 +0100, you wrote:

What is the standard key in the AS400 green-screen world for a user to
request that a scrolling screen advances/retreats one line at a time.

Obviously the Page Up/Down keys handle matters one page at a time - and in
PC applications the arrow keys usually handle one line at a time (but these
are not recognized by the 400 are they???).

Any guidance/ideas welcomed,

Thanks,

Chris