diff --git a/include/globals.h b/include/globals.h
index 949ae38..c8f2fa1 100644
--- a/include/globals.h
+++ b/include/globals.h
@@ -1,30 +1,35 @@
 #pragma once
+#include <stdint.h>
 
 typedef enum {
     LBRACK,
     RBRACK,
     LCURLY,
     RCURLY,
+    LPAREN,
+    RPAREN,
 
-    ID,
     SEMI,
     COMMA,
     ARROW,
     STAR,
+    ANDREF,
+    DOLLAR,
+
     COMMENT,
+    ID,
     NUM,
+    STRING_LITERAL,
 
     RETURN,
     IF,
     ELSE,
-
-    STRING_LITERAL,
-
+    
     ERROR
 } TokenType;
 
 typedef struct {
     TokenType type;
     char *data;
-    int line;
+    uint32_t line;
 } Token;
diff --git a/include/lex.h b/include/lex.h
index e69de29..db36da2 100644
--- a/include/lex.h
+++ b/include/lex.h
@@ -0,0 +1,39 @@
+#pragma once
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "globals.h"
+
+#define LEX_BUF_SIZE 4096
+
+typedef struct Lexer {
+    uint32_t linepos;
+    uint32_t lineno;
+
+    FILE *source;
+
+    int flag_EOF;
+
+    char *buffer;
+    char *curr;
+
+    size_t bytes_in_buffer;
+} Lexer;
+
+Lexer *new_lexer();
+
+void lexer_set_source(Lexer *lexer, FILE *source);
+
+void lexer_fill_buffer(Lexer *lexer);
+
+void lexer_consume(Lexer *lexer);
+
+char lexer_curr(Lexer *lexer);
+
+char lexer_peek(Lexer *lexer);
+
+Token lexer_next_token(Lexer *lexer);
+
+void free_lexer(Lexer *lexer);
diff --git a/src/lex.c b/src/lex.c
index e69de29..bf291da 100644
--- a/src/lex.c
+++ b/src/lex.c
@@ -0,0 +1,78 @@
+#include "lex.h"
+
+Lexer *new_lexer() {
+    Lexer *lexer = malloc(sizeof(Lexer));
+
+    lexer->linepos = 0;
+    lexer->lineno = 0;
+
+    lexer->source = NULL;
+
+    lexer->flag_EOF = 0;
+
+    lexer->buffer = calloc(LEX_BUF_SIZE, sizeof(char));
+    lexer->curr = lexer->buffer;
+    lexer->buffer[0] = '\0';
+}
+
+void lexer_set_source(Lexer *lexer, FILE *source) {
+    lexer->lineno = 0;
+    lexer->linepos = 0;
+
+    lexer->source = source;
+}
+
+void lexer_fill_buffer(Lexer *lexer) {
+    if (lexer->flag_EOF) {
+        return;
+    }
+    size_t bytes_read;
+    if (*lexer->curr == 0) {
+        bytes_read = fread(lexer->buffer, sizeof(char), LEX_BUF_SIZE, lexer->source);
+        if (bytes_read < LEX_BUF_SIZE) {
+            lexer->flag_EOF = 1;
+            lexer->buffer[bytes_read] = '\0';
+        }
+        lexer->bytes_in_buffer = bytes_read;
+    } else {
+        char tmp = lexer->buffer[LEX_BUF_SIZE - 1];
+        bytes_read = fread(lexer->buffer, sizeof(char), LEX_BUF_SIZE - 1, lexer->source + 1);
+        lexer->buffer[0] = tmp;
+        if (bytes_read < LEX_BUF_SIZE - 1) {
+            lexer->flag_EOF = 1;
+            lexer->buffer[1 + bytes_read] = '\0';
+        }
+        lexer->bytes_in_buffer = bytes_read + 1;
+    }
+
+    lexer->curr = lexer->buffer;
+}
+
+void lexer_consume(Lexer *lexer) {
+    size_t read = lexer->curr - lexer->buffer;
+    if (read >= lexer->bytes_in_buffer) {
+        return;
+    }
+    if (read == LEX_BUF_SIZE - 2) {
+        lexer_fill_buffer(lexer);
+    } else {
+        lexer->curr++;
+    }
+}
+
+char lexer_curr(Lexer *lexer) {
+    return *(lexer->curr);
+}
+
+char lexer_peek(Lexer *lexer) {
+    return *(lexer->curr + 1);
+}
+
+Token lexer_next_token(Lexer *lexer) {
+    // TODO: implement
+}
+
+void free_lexer(Lexer *lexer) {
+    free(lexer->buffer);
+    free(lexer);
+}
\ No newline at end of file