Hi, sanjana lingras
If I were you I would write the code like this.
************suppose the itab type is declear as
DATA: itab TYPE TABLE OF STRING,
w_string TYPE STRING,
w_string1 TYPE STRING.
*******From this point you fill the itab with you strings.
LOOPAT itab INTO wa_string.
CONCATENATE itab-ztext wa_string INTO itab-ztext SEPERATE BY SPACE.
ENDLOOP.
w_string1 = w_string.
CONDENCE w_string1 NO-GAPS.
NOTE: APPEND ONLY USED FOR ITAB (DATASET) OR DATABASE MODIFICATION .
Please VIEW this link about processing string http://wiki.sdn.sap.com/wiki/display/WDABAP/STRING+FUNCTIONS