The input applied to the design is called the stimulus. It mimics the input data signals which are applied to the design by the simulator tool. Stimulus used in your simulation provides an easy way to observe the design's behavior within and outside your design's range without damaging the hardware. Stimulus can be provided by interactively typing it in real time, a graphical testbench, or an HDL testbench. There are advantages and disadvantages to each method. You can decide which is right for you.
5.6.1. Interactive Stimulus
Real-time input is typed on the command or transcript line of the simulator. The input data are not saved in a separate file. This means some information must be typed in between different simulation runs. ...