If you have used them in C, then they are almost same as were in C.
From the manpage of fopen() function : -
r+ : - Open for reading and writing. The stream is positioned at
the
beginning of the file.
a+ : - Open for reading and writing. The file is created if it does
not
exist. The stream is positioned at the end of the file. Subse-
quent writes to the file will always end up at the then current
end of file, irrespective of any intervening fseek(3) or similar.
