Ascii to Binary

Hi, i'm not sure if i'm in the good place so i'm sorry if it's wrong.
I'm receiving a Serial frame in Ascii and i would like to have it in binary, but I don't know how to proceed, Can someone help me please ? Thank's
(Sorry for the bad English, I'm French)

If you mean to convert an ASCII number string to a binary number, use the function atoi() or atol().