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/*
** PI.C - Computes Pi to an arbitrary number of digits
**
** Uses far arrays so may be compiled in any memory model
*/
#include<stdio.h>
#include<stdlib.h>
#if defined(__ZTC__)
#include <dos.h>
#define FAR _far
#define Fcalloc farcalloc
#define Ffree farfree
#define Size_T unsigned long
#elif defined(__TURBOC__)
#include <alloc.h>
#define FAR far
#define Fcalloc farcalloc
#define Ffree farfree
#define Size_T unsigned long
#else /* assume MSC/QC */
#include <malloc.h>
#define FAR _far
#define Fcalloc _fcalloc
#define Ffree _ffree
#define Size_T size_t
#endif
long kf, ks;
long FAR *mf, FAR *ms;
long cnt, n, temp, nd;
long i;
long col, col1;
long loc, stor[21];
void shift(long FAR *l1, long FAR *l2, long lp, long lmod)
{
long k;
k = ((*l2) > 0 ? (*l2) / lmod: -(-(*l2) / lmod) - 1);
*l2 -= k * lmod;
*l1 += k * lp;
}
void yprint(long m)
{
if (cnt<n)
{
if (++col == 11)
{
col = 1;
if (++col1 == 6)
{
col1 = 0;
printf("\n");
printf("%4ld",m%10);
}
else printf("%3ld",m%10);
}
else printf("%ld",m);
cnt++;
}
}
void xprint(long m)
{
long ii, wk, wk1;
if (m < 8)
{
for (ii = 1; ii <= loc; )
yprint(stor[(int)(ii++)]);
loc = 0;
}
else
{
if (m > 9)
{
wk = m / 10;
m %= 10;
for (wk1 = loc; wk1 >= 1; wk1--)
{
wk += stor[(int)wk1];
stor[(int)wk1] = wk % 10;
wk /= 10;
}
}
}
stor[(int)(++loc)] = m;
}
void memerr(int errno)
{
printf("\a\nOut of memory error #%d\n", errno);
if (2 == errno)
Ffree(mf);
_exit(2);
}
int main(int argc, char *argv[])
{
int i=0;
char *endp;
stor[i++] = 0;
if (argc < 2)
{
puts("\aUsage: PI <number_of_digits>");
return(1);
}
n = strtol(argv[1], &endp, 10);
if (NULL == (mf = Fcalloc((Size_T)(n + 3L), (Size_T)sizeof(long))))
memerr(1);
if (NULL == (ms = Fcalloc((Size_T)(n + 3L), (Size_T)sizeof(long))))
memerr(2);
printf("\nApproximation of PI to %ld digits\n", (long)n);
cnt = 0;
kf = 25;
ks = 57121L;
mf[1] = 1L;
for (i = 2; i <= (int)n; i += 2)
{
mf[i] = -16L;
mf[i+1] = 16L;
}
for (i = 1; i <= (int)n; i += 2)
{
ms[i] = -4L;
ms[i+1] = 4L;
}
printf("\n 3.");
while (cnt < n)
{
for (i = 0; ++i <= (int)n - (int)cnt; )
{
mf[i] *= 10L;
ms[i] *= 10L;
}
for (i =(int)(n - cnt + 1); --i >= 2; )
{
temp = 2 * i - 1;
shift(&mf[i - 1], &mf[i], temp - 2, temp * kf);
shift(&ms[i - 1], &ms[i], temp - 2, temp * ks);
}
nd = 0;
shift((long FAR *)&nd, &mf[1], 1L, 5L);
shift((long FAR *)&nd, &ms[1], 1L, 239L);
xprint(nd);
}
printf("\n\nCalculations Completed!\n");
Ffree(ms);
Ffree(mf);
return(0);
}
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