PLEASE EXPLAIN HOW EVERYTHING IN THE NUM$\_$SUBSTRING METHOD WORKS AND WHAT THEY MEAN!!

#include

#include

#include

#include

#define MAX $10240$

#define NUM$\_$THREADS $10$

int n$1,$n$2$;

char $*$s$1,*$s$2$;

FILE $*$fp;

int countArray$[$NUM$\_$THREADS$]=\{0\}$;

$//$read input file and generate string s$1/$s$2$ and length n$1/$n$2$

int readf$($FILE $*$fp$)$

$\{$

$$ if$(($fp$=$fopen$("$strings$.$txt$","$r$"))==$NULL$)\{$

$$ printf$("$ERROR: can't open string.txt$!$

$")$;

$$ return $0$;

$\}$

$$ s$1=($char $*)$malloc$($sizeof$($char$)*$MAX$)$;

$$ if$($s$1==$NULL$)\{$

$$ printf$("$ERROR: Out of memory!

$")$;

$$ return $-1$;

$\}$

$$ s$2=($char $*)$malloc$($sizeof$($char$)*$MAX$)$;

$$ if$($s$1==$NULL$)\{$

$$ printf$("$ERROR: Out of memory

$")$;

$$ return $-1$;

$\}$

$/*$read s$1$ s$2$ from the file$*/$

$$ s$1=$fgets$($s$1,$ MAX, fp$)$;

$$ s$2=$fgets$($s$2,$ MAX, fp$)$;

$$ n$1=$strlen$($s$1)$; $/*$length of s$1*/$

$$ n$2=$strlen$($s$2)-1$; $/*$length of s$2*/$

$$ if$($s$1==$NULL $||$ s$2==$NULL $||$ n$1$