Smart Beginning of Line
Moves the cursor generally to the beginning of the current line. It does one of the following:
• If the cursor is in the middle of a line, move it to just before the first non-white space character on the line.
• If the cursor is before the first non- white space character on the line, move it to the actual start of the line.
• If the cursor is already at the start of the line, move to the start of the file.