A language L subset of or equal to X is called a cohesive prefix code
if xLy boolean AND L not equal 0 implies that y=1 and xL subset of or
equal to L for any x, y is an element of X. An example of cohesive p
refix codes is an infix code. We determine first the structure of cohe
sive prefix codes and then we study several relationships between maxi
mal infix; codes and maximal cohesive prefix codes. Finally, we determ
ine the structure of a cohesive prefix code that is a right semaphore
code.