Hi PerlMonks!.thanks for the help.. but still i am struggling with this logic... so i kind of trying with my own logic... what i am doing here is, as soon as i encounter 'EX R1,ROUTINE#2' instruction, whatever label(ROUTINE#2)it is pointing to,i am storing that label and the next line to a separate file..that is i am storing 'ROUTINE#2 ST R2,VAR1' to a an intermediate file.then parse the code from the begining.when 'EX R1,ROUTINE#2' is reached, goto the intermediate file and retreive the value corresponding to ''ROUTINE#2'and replace it with the EX statement... i hope this works..i know this is lengthy process..is there any other way i can do it? here i have reached till storing values to the intermediate values... need to do the rest....