CREW PUT WRONG FLT NUMBER IN ACARS AND THEREFORE RECEIVED WRONG ATC CLRNC ON PRE-DEP CLRNC.

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ON PREFLT OF ACARS UNIT COPLT INITIALIZED ACARS WITH INCORRECT FLT NUMBER. CLRNC OBTAINED THROUGH PRE-DEP CLRNC SYS WITH MESSAGE FROM PRE-DEP CLRNC ALT AND SQUAWK ENTERED IN APPROPRIATE BOXES. FMC PROGRAMMED. FLT DEPARTED BWI. DEP CTL INDICATED WE HAD WRONG NUMBER IN XPONDER. CAPT REMEMBERED SPECIFICALLY PUTTING IN XPONDER CODE FROM PRE-DEP CLRNC MESSAGE. UPON FURTHER INVESTIGATION; IT WAS DETERMINED THAT WRONG CLRNC WAS OBTAINED THROUGH PRE-DEP CLRNC. FORTUNATELY; IN BWI DEPARTING RWY 28; ALL DEPS CLB TO 4000 FT ON HDGS ASSIGNED BY TWR. A READBACK OF CORRECT RTING WAS OBTAINED FROM ATC AND FLT CONTINUED TO DEST. NO DEVS FROM FLT PLAN OR CLRNC FROM GND; TWR; DEP CTL OR CTR WERE MADE. PROB AROSE BECAUSE BOTH CREW MEMBERS SHARED DATA INPUT TO ALL 'BOXES;' INSTEAD OF 1 CREW MEMBER INPUTTING DATA AND THE OTHER XCHKING ALL INFO. ALSO CONTRIBUTING TO THIS ERROR WAS THE FAILURE OF 1 AND/OR BOTH CREW MEMBERS TO CHK; DOUBLE CHK; OR EVEN TRIPLE CHK ALL DATA INPUTS. AS FAR AS CONDUCT OF FLT IS CONCERNED; WE KNEW WHAT WE WERE SUPPOSED TO DO; WHERE WE WERE GOING; AND HOW TO GET THERE; HOWEVER; THE PREFLT CLRNC WE OBTAINED FROM PRE-DEP CLRNC HAPPENED NOT TO BE THE CORRECT ONE FOR OUR DEST.