This control function moves the cursor backward one column. If the cursor is at the left margin, then all screen data within the margin moves one column to the right. The column that shifted past the right margin is lost.
Available in: VT Level 4 mode only
DECBI adds a new column at the left margin with no visual attributes. DECBI is not affected by the margins. If the cursor is at the left border of the page when the terminal receives DECBI, then the terminal ignores DECBI.