What is Inter-system testing? Have you done that?

When various systems are internally connected with each other and can access or exc hange information as well as process one system with another system as interface. Real Life Example is ATM machines, if you have account in State Bank of India of any branch and you have SBI debit card. You need to withdraw cash immediately, you have ICICI bank ATM machine near you. You insert SBI debit card in ICICI bank ATM machine, you enter your credential, the system will internally access SBI server and verify your authentication details along with account balance. When you request the amount to be withdrawn, ICICI bank ATM machine will dispense the cash requested for. with amount remaining in your SBI account. Another Example is you can access and use all banking related functionality from different branch of SBI bank across India.