Octal Value for UNIX file permissions

Can anyone explain to me how to convert a octal value for UNIX file permissions to a text value to display on screen. For example I need to write code in C++ that would take in octal value 100666 and display rw-rw-rw

I have found this information but still can not figure out the conversion.

Octal digit Text equivalent Binary value Meaning
0 --- 000 All types of access are denied
1 --x 001 Execute access is allowed only
2 -w- 010 Write access is allowed only
3 -wx 011 Write and execute access are allowed
4 r-- 100 Read access is allowed only
5 r-x 101 Read and execute access are allowed
6 rw- 110 Read and write access are allowed
7 rwx 111 Everything is allowed