Understanding the problem

To better understand a hash table, let us first look at some common problems programmers face when designing software systems. When writing a program, we often need to map different data types together, such as the roll number of all students in a class. We need some data structure that stores the mapping between data of different types. The names of all students are strings, while their roll numbers might be positive integer values. 

One way to store these mappings is in two separate arrays at the same indices.