Operator: The operator will be responsible for the following operations:

Turning the ATM ON/OFF using the designated Key-Switch.

Refilling the ATM with cash.

Refilling the ATM’s printer with receipts.

Refilling the ATM’s printer with INK.

Take out deposited cash and checks.

Customer: The ATM customer can perform the following operations:

Balance inquiry: the user can view his/her account balance.

Cash withdrawal: the user can withdraw a certain amount of cash.

Deposit funds: the user can deposit cash or checks.

Transfer funds: the user can transfer funds to other accounts.

Bank Manager: The Bank Manager can perform the following operations:

Generate a report to check total deposits.

Generate a report to check total withdrawals.

Print total deposits/withdrawal reports.

Checks the remaining cash in the ATM.

https://github.com/tssovi/grokking-the-object-oriented-design-interview/blob/master/object-oriented-design-case-studies/design-an-atm.md

An ATM machine allows a user to deposit and withdraw cash. It also allows a user to see his balance. How do you design such a system? What are your main challenges?

Requirements Of The System

With all the basic functions of a typical ATM machine in mind, these are the requirements of the system we will design:

A user with a bank account and an ATM card can insert the card in the machine.

The ATM authenticates the user with a pin before allowing transactions.

Once authenticated, the user can make a balance inquiry, deposit cash or check, withdraw cash or transfer funds to another account.

At any instant of time, the system only allows a single transaction.

The system displays a success or failure message to the user at the end of the transaction to indicate the completion of a transaction.

After the completion of a transaction, the user can start another transaction.

If no other transaction is to be made, the system returns the card to the user. 

https://medium.com/double-pointer/system-design-interview-atm-machine-design-80c90b044a35