What does the term 'Input' mean in the context of programming or systems?

The term 'Input' in programming usually refers to data or signals that a system, program, or function receives from outside for processing. For example, in Java, a method can accept parameters — these are its input data. In user interfaces, input refers to user actions such as keystrokes or text entry.

Example in Java:

public int sum(int a, int b) {
    return a + b; // a and b are the method's input
}