diff --git a/labs/04/lex_analaizer.l b/labs/04/lex_analaizer.l
new file mode 100644
index 0000000..3c5767f
--- /dev/null
+++ b/labs/04/lex_analaizer.l
@@ -0,0 +1,39 @@
+%{
+#include <stdio.h>
+%}
+
+%option noyywrap
+
+%%
+\/\/[^\n]*              printf("COMMENT\n");
+
+i                       printf("intdcl\n");
+f                       printf("floatdcl\n");
+p                       printf("print\n");
+
+[a-eg-hj-oq-z]          printf("id\n");
+[0-9]+                  printf("inum\n");
+[0-9]*\.[0-9]           printf("fnum\n");
+
+\=                      printf("assign\n");
+\+                      printf("plus\n");
+\-                      printf("substraction\n");
+\*                      printf("multiplication\n");
+\/                      printf("division\n");
+
+[ \t]+
+\n
+.
+%%
+
+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;
+}
\ No newline at end of file