IBM 5280 Distributed Data System - Index of

REFRESH AREAS FOR THE STATUS LINESThere are two status line refresh buffers in keyboard/display storage for each unit.These buffers are referred to as status line 1 buffer and status line 2 buffer. Thestatus line 1 buffer is used as a refresh area for the status line of a single datastation or station 0 of a dual-display data station. The status line 2 buffer is usedas a refresh area for the status line of station 1 of a dual data station. The statusline is usually displayed on row one of the screen. However, if a screen formatuses all of the rows on the screen, the status line can be removed from the screenso that row one of the format can be displayed on row one of the screen. The statusline is maintained in the status line refresh buffer whether or not it is being displayedon the screen.D ISPLA V CONTROL AR EAThe display control area contains:• Display attributes for the beginning of each row on the display screen.• The refresh buffer address of the first position of the row.• Control registers that provide control for the upper and lower halves of thedisplay screen.• Cursor address registers that provide the current refresh buffer address of thecursor.The display control area begins with strings of 3-byte entries; one entry for eachrow on the display screen.The first byte of a 3-byte entry contains the display attributes for each row. Theformat of the first byte is:BitsAttribute Description0-1 System indicator:00 = None01 = None10 = Dash11 = Sol id rectangle2 Valid row starting attribute. This bit must be 1 in order for bits 3through 7 to be effective.3 1 = Column separator.4 1 = Blink.5 1 = Underscore.6 1 = High intensity.7 1 = Reverse image.Note: If bits 5, 6, and 7 are all on (111), no data is displayed.Keyboard/Display Storage 127