However are Numbers and Characters Stored in Oracle

1. For integers others than those in tens (i.e. 10, 100...), 1-99 is stored using 2 bytes, 101~999 using 3 bytes...
2. For integers in tens, their trailing 0s are not used any extra bytes. E.g. 100000000 still uses 2 bytes. Not sure how does Oracle achieve it?
3. For characters, each character is stored using 1 bytes.
4. So if you need to store single digit like '0' or '1' indicator, better to store it as VARCHAR2(1), not NUMBER(1).

You can use vsize to verify.