[c] found some old c progs

c/README.org

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+#+TITLE: C
+
+ - [[./pi-val.c][pi-val.c]]: Approximating value of pi
+ - [[./pi-val-leibnitz.c][pi-val-leibnitz.c]]: Approximating value of pi using Ramanjuan's method
+ - [[./pi-val-ramanjuan.c][pi-val-ramanjuan.c]]: Approximating value of pi using Leibnitz's method
+

c/pi-val-leibnitz.c

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+// Originally written in 2015
+
+#include<stdio.h>
+#define ACCURACY 1
+int main()
+{
+    int sign=1, n, ctr=0;
+    double i, pi=ACCURACY;
+    printf("Enter the value of n: ");
+    scanf("%d", &n);
+    for(i=3; i<n; i=i+2)
+    {
+        sign*=-1;
+        pi+=((sign*((double)(1/i)))*ACCURACY);
+        //printf("%.20lf\n", pi);  // SAME AS pi=pi+( sign* ( (double)(1/i) ) );
+    }
+    pi*=4;
+
+    printf("The value of pi is: %.20lf\n", pi);
+    return 0;
+}
+
+/*
+Enter the value of n: 1
+The value of pi is: 4.00000000000000000000
+
+Enter the value of n: 10
+The value of pi is: 3.33968253968254025210
+
+Enter the value of n: 100
+The value of pi is: 3.12159465259101098766
+
+Enter the value of n: 1000
+The value of pi is: 3.13959265558978506405
+
+Enter the value of n: 99999
+The value of pi is: 3.14161265398978528651
+
+Enter the value of n: 999999
+The value of pi is: 3.14159465359369205473
+*/

c/pi-val-ramanjuan.c

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+// Originally written in 2015
+
+#include<stdio.h>
+#include<math.h>
+double pow1(int base, int power)
+{
+    double p=1;
+    int j=0;
+    for(; j<power ; ++j)
+    {
+        p*=base;
+    }
+    return p;
+}
+
+double factorial(int a)
+{
+    int j=a;
+    double f=1;
+    for(; j>1; --j)
+    {
+        f*=j;
+    }
+    return f;
+}
+
+int main()
+{
+    int k, i;
+    double pi=0;
+    printf("Enter the value of k: ");
+    scanf("%d", &k);
+    for(i=0; i<k; ++i)
+    {
+        pi+=((factorial(4*i) * (1103 + (26390*i))) / (pow1(factorial(i), 4) * pow1(396, 4*i)) );
+    }
+    pi*=(double) ( ( 2 * sqrt(2) ) / ( 9801 ) );
+    pi = (double) ( 1 / pi );
+    printf("The value of pi using Ramanujan's equation is: %.20lf\n", pi);
+    return 0;
+}
+
+/*
+Enter the value of k: 1
+The value of pi using Ramanujan's equation is: 3.14159273001330552333
+
+Enter the value of k: 2
+The value of pi using Ramanujan's equation is: 3.14159265358979356009
+
+Enter the value of k: 10
+The value of pi using Ramanujan's equation is: 3.14159265358979311600
+
+Enter the value of k: 100
+The value of pi using Ramanujan's equation is: -nan
+*/

c/pi-val.c

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+// Originally written in 2015
+
+#include<stdio.h>
+int main()
+{
+    int sign=1, n;
+    double i, pi=1;
+    printf("Enter the value of n: \n");
+    scanf("%d", &n);
+    for(i=3; i<n; i=i+2)
+    {
+        sign*=-1;
+        pi+=(sign*((double)(1/i)));
+        //printf("\n%lf", pi);  // SAME AS pi=pi+( sign* ( (double)(1/i) ) );
+    }
+    pi*=4;
+    printf("The value of pi is: %lf\n", pi);
+    return 0;
+}
+
+/*
+Enter the value of n:
+10
+The value of pi is: 3.339683
+
+Enter the value of n:
+1000
+The value of pi is: 3.139593
+
+Enter the value of n:
+9999
+The value of pi is: 3.141793
+
+Enter the value of n:
+99999
+The value of pi is: 3.141613
+
+Enter the value of n:
+999999
+The value of pi is: 3.141595
+
+Enter the value of n:
+9999999
+The value of pi is: 3.141593
+
+Enter the value of n:
+999999999
+The value of pi is: 3.141593
+ */