how to make a key in unity code example

Example 1: unity key detection

if (Input.GetKeyDown(KeyCode.Space))
        {
            print("space key was pressed");
        }

Example 2: Debug.Log(Input.GetKey)

void Update()
{
    //get the input
    var input = Input.inputString;

    //ignore null input to avoid unnecessary computation
    if (!string.IsNullOrEmpty(input))
    {
        switch(input)
        {
            case 'a': break;
            case 'b': break;
        }
    }
}