What is the key difference between a system call and a procedure call $($i$.$e$.,$ a call to a library routine$)?$Including the initial parent process, how many processes are created by the program shown below? $[$You can reason, or modify the program by adding printf$()$ statement to see the number of processes created.$]$

#include

#include

int main$()\{$

int i;

for $($i $=0$; i $<4$; i$++)$

fork$()$;

return $0$;Including the initial parent process, how many processes are created by the program shown below? $[$You can reason, or modify the program by adding printf$()$ statement to see the number of processes created.$]$