diff --git a/src/lc3_lib.h b/src/lc3_lib.h
index b9858a2..ffe18e5 100644
--- a/src/lc3_lib.h
+++ b/src/lc3_lib.h
@@ -22,6 +22,9 @@ int read_image(const char* file);
 void disable_input_buffering();
 void restore_input_buffering();
 
+/* check key - unix or win */
+uint16_t check_key();
+
 /* Write to memory address */
 void mem_write(uint16_t address, uint16_t val);
 
@@ -29,4 +32,4 @@ void mem_write(uint16_t address, uint16_t val);
 int mem_read(uint16_t address);
 
 /* Handle interrupt */
-void handle_interrupt(int signal);
\ No newline at end of file
+void handle_interrupt(int signal);