Is/are there any function(s) in C that convert(s) character/ASCII/Decimal to binary and vice versa?
what about bcopy and strcpy?
An individual ASCII character is already binary. For strings representing numbers, there's the sscanf, atoi, atof functions and other related ones. See their man pages.
sprintf is a general-purpose formatting tool that can output many formats as readable ASCII. See its manual page.
they copy bytes and strings. They don't modify them at all.