2.2 The IBM 7171 ASCII Device Attachment Control Unit - Index of

cursor will be moved to the first unprotected character to the right of thenewline left margin.Undent KeyThe Undent sequence repositions the cursor one tab stop to the left of itscurrent position and sets the Newline left margin to the new cursor position. Ifthe Undent key is pressed and there is no column tab stop to the left of thecurrent location, the cursor will be moved to the physical beginning of thecurrent line.Column Tab keyThe Column Tab sequence repositions the cursor at the next tab stop to theright, without regard for protected fields. The tab stops may be set by theapplication program or by the terminal user.Column Backtab keyThe Column Backtab sequence repositions the cursor at the next tab stop to theleft, without regard for protected fields. The tab stops may be set by the applicationprogram or by the terminal user.Editing KeysEnter/Exit Insert Mode ToggleThe Insert Mode sequence puts the terminal into insert mode. Repeating theInsert Mode sequence releases the terminal from insert mode. All charactersentered into unprotected fields overtype data already in those particular screenbuffer positions.Delete CharacterThe Delete sequence indicates that the character in the current cursor positionis to be deleted and everything else in that field moves one character to the left.If the field wraps from the end of the current line to the beginning of the next,the leftward movement of characters also wraps.Erase to End of FieldThe Erase to End of Field sequence causes the erasure of all unprotected dataat and beyond the current cursor position up until the next field attribute.There is no cursor repositioning as a result of this sequence.Erase InputThe Erase Input sequence causes commands to be sent to the terminal whichchanges all unprotected data areas in the screen buffer to nulls and repositionsthe cursor to the first unprotected character location on the screen.RuboutThe Rubout sequence functions as a destructive backspace. Only unprotectedfields can be affected by this function. If the Rubout function is invoked andthe cursor can move left and remain in an unprotected field, then the characterat that position will be deleted.Host Attention Keys: All of the keys listed in this section signal the host CPU via anAttention that input has been completed and that the device requires service fromthe host. The host should respond with a Read Modified command to pick up theAttention Identifier (AID) byte as well as the input generated at the device.Chapter 4. Customizing IBM 7171 Tables 4-7