Following 4 can be used correctly as variable names or identifiers. Identifier PIN_4 numb_er _SIMPLE_INTEREST
Notes
4PIN //This is not as it starts with a number
PIN_$ //This contains $ which is not allowed Identifier //This is OKAY PIN_4 //This is OKAY
P.I.N. //This is not as it contains . which is not allowed numb_er //This is OKAY. _ is allowed
Srl.No. ////This is not as it contains . which is not allowed _SIMPLE_INTEREST //This is OKAY. _ is allowed at first position also
FOUR@IDENTIIFERS //This is not as it contains @
FOUR NAMES //This is not as it contains space character.