abap code error

Hi all,

I'm getting an error for the following code. Can anyone plz help me in this, i'm a fresher in abap.

REPORT ZREPORT_1.

WRITE: / 'Welcome' SY-UNAME.

/ 'U have logged in on' SY-DATUM.

i want the output as:

Welcome aaaa

U have logged in on 07/08/2010.

i'm getting the error as:

Unable to inerpret "SY-UNAME". Possible causes: Incorrect spelling or comma error.

please guide me.