http://www.gnu.org/software/emacs/manual/html_node/Horizontal-Scrolling.html

C-x
    Scroll to the right (scroll-right).
…

http://www.linuxselfhelp.com/gnu/emacs/html_chapter/emacs_15.html#SEC84

If the variable truncate-lines is non-nil, then each line of text gets just one screen line for display; if the text line is too long, display shows only the part that fits. If truncate-lines is nil, then long text lines display as more than one screen line, enough to show the whole text of the line. See section Continuation Lines. Altering the value of truncate-lines makes it local to the current buffer; until that time, the default value is in effect. The default is initially nil.