diff --git a/labs/04/lex_analyzer.l b/labs/04/lex_analyzer.l
new file mode 100644
index 0000000..38b1b6f
--- /dev/null
+++ b/labs/04/lex_analyzer.l
@@ -0,0 +1,41 @@
+%{
+#include <stdio.h>
+%}
+
+%option noyywrap
+%%
+"//".*                  printf("COMMENT"); 
+i                       printf("intdcl ");
+f                       printf("floatdcl ");
+p                       printf("print ");
+[a-eg-hj-oq-z]          printf("id ");
+[0-9]+                  printf("inum ");
+[0-9]*\.[0-9]{1,5}      printf("fnum ");
+\=                      printf("assign ");
+\+                      printf("plus ");
+\-                      printf("minus ");
+\*                      printf("multiplied_by ");
+\/                      printf("divided_by ");
+\^                      printf("power ");
+\*\*                    printf("square ");
+\(                      printf("open_parenthesis ");
+\)                      printf("close_parenthesis ");
+\[                      printf("open_square_bracket ");
+\]                      printf("close_square_bracket ");
+\{                      printf("open_curly_bracket ");
+\}                      printf("close_curly_bracket ");
+\n                      printf("\n");
+[ \t]+                  /* ignore whitespace */
+%%
+
+int main(int argc, char **argv) {
+    if (argc > 1) {
+        yyin = fopen(argv[1], "r");
+        if (!yyin) {
+            perror("Error opening input file");
+            return 1;
+        }
+    }
+    yylex();
+    return 0;
+}