diff --git a/parser.py b/parser.py
index fead75d..1e6b5f1 100644
--- a/parser.py
+++ b/parser.py
@@ -3,6 +3,13 @@
 import ply.lex as lex
 
 class LLVMLexer(object):
+    current_string = ""
+    line_begin = 0
+
+    states = [
+        ('string', 'exclusive')
+    ]
+
     reserved = {
         'if': 'IF',
         'then': 'THEN',
@@ -57,6 +64,7 @@ class LLVMLexer(object):
     ]
 
     t_ignore = ' \t'
+    t_string_ignore = ''
     t_ASTERIX = r'\*'
     t_LPAREN = r'\('
     t_RPAREN = r'\)'
@@ -81,20 +89,63 @@ class LLVMLexer(object):
     def t_newline(self, t):
         r'\n+'
         t.lexer.lineno += len(t.value)
+        self.line_begin = t.lexpos
+
+
+    def t_string_newline(self, t):
+        r'\n'
+        print("{}:{}: Newline is not allowed inside strings."
+              .format(t.lineno, t.lexpos - self.line_begin))
+        t.lexer.lineno += 1
+        self.line_begin = t.lexpos
+
 
     def t_INT(self, t):
         r'\d+'
         t.value = int(t.value)
         return t
 
+    def t_begin_string(self, t):
+        r'c\"'
+        t.lexer.begin('string')
+        self.current_string = ""
 
-    def t_STRING(self, t):
-        r'c"[^"]*"'
-        value = t.value[2:-1]
-        t.value = value
+    def t_string_doublequote(self, t):
+        r'\\"'
+        self.current_string += '"'
+
+
+    def t_string_backslash(self, t):
+        r'\\\\'
+        self.current_string += '\\'
+
+
+    def t_string_hex(self, t):
+        r'\\[0-9a-f][0-9a-f]'
+        code = int(t.value[1:], 16)
+        self.current_string += chr(code)
+
+
+    def t_string_singlebackslash(self, t):
+        r'\\'
+        print("{}:{}: Single backslash is not allowed inside strings."
+              .format(t.lineno, t.lexpos - self.line_begin))
+
+
+    def t_string_end(self, t):
+        r'"'
+        t.value = self.current_string
+        self.current_string = ""
+        t.type = "STRING"
+        t.lexer.begin('INITIAL')
         return t
 
 
+    def t_string_meat(self, t):
+        r'.'
+        self.current_string += t.value
+
+
     def t_ID(self, t):
         r'[a-zA-Z0-9_-]+'
         t.type = self.reserved.get(t.value, 'ID')
@@ -112,13 +163,16 @@ class LLVMLexer(object):
         return t
 
 
-    def t_error(self, t):
-        print("{}:{}: Illegal character '{}'".format(t.lineno, t.lexpos, t.value[0]))
+    def t_ANY_error(self, t):
+        print("{}:{}: Illegal character '{}'"
+              .format(t.lineno, t.lexpos - self.line_begin, t.value[0]))
         t.lexer.skip(1)
 
+
     def build(self, **kwargs):
         self.lexer = lex.lex(module=self, **kwargs)
 
+
     def test(self, data):
         self.lexer.input(data)
         for tok in self.lexer:
@@ -128,6 +182,7 @@ class LLVMLexer(object):
 if __name__ == '__main__':
     m = LLVMLexer()
     m.build()
-    data = '''123 456 c"abc" def add sdiv ; some comment
+    data = r'''123 456 c"abc _\2c_ \" \\ and so on" def add sdiv ; some comment
+    qqq
     '''
     m.test(data)