The KMP_21000603.cpp file should be kept in the same folder as pattern1.txt and text1.txt files 
line 9 , 10 , 11 should be changed to the relavent file names 
Ex:
string input_Pattern = "pattern5.txt" ; 
string input_Text = "text5.txt"; 
string output_file = "patternmatch5.txt" ; 

Then the program can be run