Given a Turing machine M and x in $\{0,1\},$ let t$($M$,$ x$)$ denote the number of distinct tape cells that the

tape$-$head visits during the computation of M on input x$.$ Define

Sublinear $=\{$M $$ : $$x in $\{0,1\},$ t$($M$,$ x$)<|$x$|$