Waring 1, 2 and 3:
You are comparing a character with a character pointer.
This is wrong, change char clientname to char clientname[20] (in function add_record, delete_record and search).
Also do this for street_address, city, pros, country and postalorzip_code (and don't use the & in the scanf function when passing a character pointer/array).
B.t.w. you can't compare 2 strings with the == operator. Use the strcmp function instead.
Warning 4 and 5:
dta_file is a filepointer. You must open the file before reading/writing.
