unity if input.getkeydown code example

Example: if(keydown unity)

using UnityEngine;
using System.Collections;

public class classExample : MonoBehaviour{
  
  // variables:
  public float speed;
  public bool grounded
    
  public RigidBody rb;
  
  void Update(){
   
    // on button press / key press here:
    if(Input.GetKeyDown(keycode.W)){
     
      rb.addForce = new vector3(_, _, _); 
      // If you want to add a force then put this line of code on one of the "_"'s:
      // (speed * Time.deltaTime;)
      
    }
    
    // add more movement here if you need:
    // (just remember to change to keycode)
  }
  
  private void onCollisionEnter(Collsion, collision){
   
    grounded = true;
  }
  
  private void onCollisionExit(Collsion, collision){
   
    grounded = false;
  }
    
}