Expression denotes a `type', where a `variable', `value' or `method group' was expected

Sorry, apparently this question is asked a lot but I couldn’t figure it out from other answers. Here is my code:

if (Input.GetButtonDown (Space) && obj.transform.position.y == 0.5F)
			while(obj.transform.position.y <= jumpheight)
				obj.transform.position.y += jumpspeed;

What is wrong here ?

Change Input.GetButtonDown (Space)

to this: Input.GetKeyDown (KeyCode.Space)

or this: Input.GetButtonDown ("jump")

if you want to use “space”, then you’ll need to create a new input setting (Edit → Project Settings → Input)

Well, Input.GetButtonDown() takes a string, not an enum from what I can see. Check out the Unity Documentation for Input.