Error using strlen () results that appear ...

Write the first word of a string into another array to write the program as follows

The result is a bit unexpected and re-enter a string, the result is unexpectedly as I have thought that this function is characters stop, but after several input why there is a difference? Tried several different lengths of strings, and found that the first space appeared right after the nineth character, and that it would be wrong to appear before the 9th one! Then I tried the next keyword sizeof () it no matter how long the input string is fixed value 8;

A pointer to a function or an array form parameter does not pass the memory occupied by the data pointed to by the pointer, only passing one address

Error using strlen () results that appear ...