Abstract: In a CRT display system, its screen is divided into a least two partitions or viewports for displaying different data groups, and characters in one of the groups can be vertically scrolled bit by bit in one of the partitions. The partition to be scrolled is defined by line attributes assigned to successive rows of the screen. When a raster scan passes the scrolling partition, a line count output of a (scan) line counter is modified by adding a content of a smooth scroll offset register to the line count. The modified line count is used together with a character code as an address for a character generator. By gradually changing the content of the offset register, the characters are vertically shifted smoothly in the partition.