American Express Internship interview questions

I had to interview with 2 different people, each of them asked me a few technical questions and a few logical questions. The technical questions were about the difference between pass by value and pass by reference. What is a primary key.

The whole process consists of one online written test having technical multiple choice questions and two programming questions, it was supporting c, c++, java, python. Selected students were called for technical interview. Selects were called for HR interview. HR round was difficult, they just asked anything actually it was HR plus technical.