A turing machine that accepts the language of all strings over {a,b}
with equal numbers of a's and b's

Transition table:

 0   1   R
 1   h   S
 1 a 2 a R
 1 b 2 b R
 2   3   L
 2 a 2 a R
 2 b 2 b R
 3   h   S
 3 a 4   L
 3 b 6   L
 4 a 5   L
 4 b 3   L
 5 a 5 a L
 5 b 2 a R
 6 a 3   L
 6 b 7   L
 7 b 7 b L
 7 a 2 b R

 - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Yp:s/</<live:/
:s/<live:h>/<h>/
:s/<live:c:/<c:/
:s/>$/> /
:s/<live:0> / <run:1>/
:s/<live:1> /<run:h> /
:s/<live:1>a/a<run:2>/
:s/<live:1>b/b<run:2>/
:s/<live:2> /<left:3> /
:s/<live:2>a/a<run:2>/
:s/<live:2>b/b<run:2>/
:s/<live:3> /<run:h> /
:s/<live:3>a/<left:4> /
:s/<live:3>b/<left:6> /
:s/<live:4>a/<left:5> /
:s/<live:4>b/<left:3> /
:s/<live:5>a/<left:5>a/
:s/<live:5>b/a<run:2>/
:s/<live:6>a/<left:3> /
:s/<live:6>b/<left:7> /
:s/<live:7>b/<left:7>b/
:s/<live:7>a/b<run:2>/
:s/ <left:3>/<run:3> /
:s/ <left:4>/<run:4> /
:s/ <left:5>/<run:5> /
:s/ <left:6>/<run:6> /
:s/ <left:7>/<run:7> /
:s/a<left:3>/<run:3>a/
:s/a<left:4>/<run:4>a/
:s/a<left:5>/<run:5>a/
:s/a<left:6>/<run:6>a/
:s/a<left:7>/<run:7>a/
:s/b<left:3>/<run:3>b/
:s/b<left:4>/<run:4>b/
:s/b<left:5>/<run:5>b/
:s/b<left:6>/<run:6>b/
:s/b<left:7>/<run:7>b/
:s/<live:/<c:/
:s/ $//
:s/ $//
:s/<run:/</
h