1. What is the diff erence between the strcasecmp() function 

strcasecmp will compare the strings using case
sensitivity. strcmp will ignore case!.

2. Why is the lowercase “a” considered to occur later in the 
alphabet than the uppercase “A”?

the lowercase 'a' has lower ASCII code than the uppercase "A" and the computer sorts them by ASCII code not alphanumeric
character

3. Explain the diff erence between the similar_text() function 
and the levenshtein() function.

similar_text() comparethe similarity between string ... ie.