Inital commit

subnetcalc.c

@@ -0,0 +1,38 @@
+/* A very simple subnet calculator in C, written by
+ * Jack-Benny Persson (jack-benny@cyberinfo.se).
+ * Released under GNU GPLv2.
+*/
+
+#include <stdio.h>
+#include <math.h>
+
+int main(void)
+{
+    int net;
+    double hosts;
+    double addr;
+    printf("Enter netmask in slash-notation without the slash: ");
+    scanf("%2d", &net);
+
+    if (net >= 0 && net <= 32) // Sanity check the user input
+    {
+        printf("Netmask bit: %d\n\n", net);	
+        addr = pow(2, 32-net); // Calculate number of addresses
+        printf("%.0lf total addresses\n", addr);
+
+        hosts = addr-2; 
+        if (hosts < 0)   // Check if number of usable hosts is a negative value
+        {
+            hosts = 0;   // Set usable hosts to zero if it was negative
+        }   
+        printf("%.0lf usable addresses for hosts\n", hosts);
+        return 0;
+    }
+    else  // If the user entered anything else than 0-32
+    {
+        printf("Only values between 0-32 are accepted\n");
+        return 1;
+    }
+
+    return 1;
+}