1 files changed, 25 insertions, 0 deletions
diff --git a/reference/C/CONTRIB/SNIP/isisbn.c b/reference/C/CONTRIB/SNIP/isisbn.c
new file mode 100755
index 0000000..6fccee7
--- /dev/null
+++ b/reference/C/CONTRIB/SNIP/isisbn.c
@@ -0,0 +1,25 @@
+/*
+**  ISISBN.C - Validate International Standard Book Numbers (ISBNs)
+**
+**  public domain by Maynard Hogg
+*/
+
+#include <ctype.h>
+
+int isbn2(char *str)
+{
+      int i = 0;
+      int test = 0;
+      int c;
+
+      while ('\0' != (c = *str++))
+      {
+            if (isdigit(c))
+                  c -= '0';
+            else if (i == 9 && 'X' == c)
+                  c = 10;
+            else continue;
+            test += c * ++i;
+      }
+      return (i == 10 && test % 11 == 0);
+}