>Why some of my report preview in smaller screen some in maximum? Can I made my report display always in full screen.

Send CTRL+F10 to maximize the report window, but only if the report has some data to display.

SELECT * FROM blah into cReport

IF _TALLY > 0
 KEYBOARD '{CTRL+F10}'
 SELECT cReport
 REPORT FORM rMyReport PREVIEW
ELSE
 WAIT WINDOW "NO DATA"
ENDIF