ASCII(char)   Converts char into a decimal ascii code

select ASCII('A') from dual

Result : 65

even though you insert multiple lerttrs , it will only pick the first letter

eg

select ASCII('ABC') from dual

Result : 65

AVG([DISTINCT]n) - Averge value of 'n' ignoring NULLs

CEIL(n)       Round n up to next whole number.

select CEIL(50.3)  from dual

Result :
51

select CEIL(50.00001)  from dual

Result :
51