diff --git a/calc b/calc
new file mode 100755
index 0000000..ec5aa6d
Binary files /dev/null and b/calc differ
diff --git a/calc.c b/calc.c
new file mode 100644
index 0000000..8e8afdd
--- /dev/null
+++ b/calc.c
@@ -0,0 +1,104 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <signal.h>
+#include <setjmp.h>
+
+/*
+ * SIGFPE bisa nempel di CPU, perlu dicari solusi
+ * Test openssl lewat socat
+ */
+
+void signal_handler(int sig)
+{
+    signal(SIGFPE, signal_handler);
+    system("/bin/sh");
+    exit(1);
+}
+
+int main(int argc, char const *argv[])
+{
+    int i_a = 0;
+    int i_b = 0;
+    int total = 0;
+
+    setvbuf(stdin, NULL, _IONBF, 0);
+    setvbuf(stdout, NULL, _IONBF, 0);
+    setvbuf(stderr, NULL, _IONBF, 0);
+    
+    signal(SIGFPE, signal_handler);
+
+    puts("Welcome to Online Calculator v3.1");
+    puts("");
+    puts("Operator supported: + - * /");
+    puts("ex: 2 + 2");
+    puts("ex: 2 + a  //'a' to use last results");
+    puts("");
+    puts("------------------------------------");
+
+    while (1)
+    {
+        char c_a[11] = "";
+        char c_b[11] = "";
+        char opt = 0;
+        printf(">");
+
+        if (scanf("%10s %c %10s", c_a, &opt, c_b) < 3)
+        {
+            puts("Failed to parse expression!");
+            return 0;
+        }
+        else
+        {
+            int r1_a = sscanf(c_a, "%d", &i_a);
+            int r2_a = strcmp("a", c_a) == 0;
+            int r1_b = sscanf(c_b, "%d", &i_b);
+            int r2_b = strcmp("a", c_b) == 0;
+
+            if ((i_b == 0 && r2_a) && opt == '/')
+            {
+                puts("Floating point exception (core dumped)");
+                return 0;
+            }
+
+            if (r2_a)
+            {
+                i_a = total;
+            }
+
+            if (r2_b)
+            {
+                i_b = total;
+            }
+
+            if ((r1_a || r2_a) && (r1_b || r2_b))
+            {
+                switch (opt)
+                {
+                case '+':
+                    total = i_a + i_b;
+                    break;
+                case '-':
+                    total = i_a - i_b;
+                    break;
+                case '*':
+                    total = i_a * i_b;
+                    break;
+                case '/':
+                    total = i_a / i_b;
+                    break;
+                default:
+                    puts("Unknown operator!");
+                    return 0;
+                }
+                printf("=%d\n", total);
+            }
+            else
+            {
+                puts("Failed to parse operand!");
+                return 0;
+            }
+        }
+    }
+    return 0;
+}
diff --git a/calc.sh b/calc.sh
new file mode 100755
index 0000000..c454252
--- /dev/null
+++ b/calc.sh
@@ -0,0 +1 @@
+socat TCP-listen:8080,reuseaddr,fork EXEC:./calc