compile your program for debug then when the core file is created use debugger on it to see where the problem is.
Suggestion: your program makes no input validations. How does it know that argv[1] contains an integer between 0 and 20? what happens if I enter 500 as argv[1] ?
int cstr[20]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; // stores c-values from distance string
int fstr[20]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}; // stores f-values from c-str giving probability of page faults
you can simplify the above like below. It is not necessary to specify the initialization of each element of the array because the compiler will set all unspecified initializer to 0 for you.
int cstr[20]={0}; // stores c-values from distance string
int fstr[20]={0}; // stores f-values from c-str giving probability of page faults
>> while (!feof(in))
we have said many many times on these boards that you should not rely on feof() because it does not always catch eof-of-file at the right time. Instead you should code it like this:
while( fgets(ea, 2, in) )
{
// blabla
}
Where is pointer
ea allocated? I see where it is declared and left unitialized, but I don't see where you allocated any memory for it. That may explain the seg fault you are getting.
for(i=0;i<dsn;i++)
{
printf("%d ",diststr[i]);
switch(diststr[i])
{
why did you make this do difficult? you don't need that switch statement
for(i=0;i<dsn;i++)
{
printf("%d ",diststr[i]);
if( diststr[i] < 20)
cstr[diststr[i]]++;
else
cstr99++;
}
Unsolved 
