Add some theory for Loops

c_modern_approach/Loops/theory.c

@@ -0,0 +1,15 @@
+#include <stdio.h>
+void goto_check() {
+  int d, n;
+  for (d = 2; d < n; d++) {
+    if (n % d == 0) {
+      goto done;
+    }
+  }
+done:
+  if (d < n)
+    printf("%d is divisable by %d\n", d, n);
+  else
+    printf("%d is prime", d);
+}
+int main() { goto_check(); }