columns = 0 DEC set columns per page.
Modern terminals don't have a fixed width and users generally expect the terminal to keep the size they assigned to the terminal. This control violates that expectation.
If columns = 0 or columns = 80, resize the terminal to width 80. If columns = 132, resize the terminal to width 132.
If the cursor position is right of the right-most column after the resize move it to the right-most column.
Also updates the state of 132 column mode.