bridge voltage calculator in C from command line

bridge_v.c

@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+
+// compile on linux as
+// gcc -o br bridge_v.c
+//
+// run as
+// ./br 10 10 10 10.1
+//
+int main(int argc, char **argv)
+{
+
+    double r1, r2, r3, r4;
+    double v = 5.0;
+
+    if (argc != 5) {
+        printf(" usage: %s R1 R2 R3 R4 \n", argv[0]);
+        printf(" usage: resistances in k Ohm\n"    );
+    } else {
+
+        r1 = atof(argv[1])*1000.0;
+        r2 = atof(argv[2])*1000.0;
+        r3 = atof(argv[3])*1000.0;
+        r4 = atof(argv[4])*1000.0;
+
+        printf(" Voltage diff == %f\n", v * (r2 * r3 - r1 * r4) / ((r1 + r3) * (r2 + r4)));
+    }
+
+}