// labc.tm
// accept the language L = { a^n b^n c^n | n>0 } 
// use check off  a->X, b->Y, c->Z  accept on XY*Z*

final q6
start q0
limit 100
trace all

q0  a  q1  X  R  // mark off one a
q0  Y  q4  Y  R  // no more a's check for no more b's and c's

q1  a  q1  a  R  // skip a's  
q1  Y  q1  Y  R  // skip Y's
q1  b  q2  Y  R  // mark off one b

q2  b  q2  b  R  // skip b's
q2  Z  q2  Z  R  // skip Z's
q2  c  q3  Z  L  // mark off one c, go to rewind

q3  a  q3  a  L  // rewind
q3  b  q3  b  L  // rewind
q3  Y  q3  Y  L  // rewind
q3  Z  q3  Z  L  // rewind
q3  X  q0  X  R  // stop rewind, look for 'a'

q4  Y  q4  Y  R  // skipping Y's must have only Z's
q4  Z  q5  Z  R  // now should have only Z's

q5  Z  q5  Z  R  // any thing except Z or end-of-tape dies
q5  #] q6  ## N  // accept

q6  #] q6  ## N  // done, off end accept

enddef

tape  abc          accept
tape  aabbcc       accept
tape  aabc         reject