diff --git a/builtins/builtins.go b/builtins/builtins.go
index 331eb5b..bec2689 100644
--- a/builtins/builtins.go
+++ b/builtins/builtins.go
@@ -45,6 +45,11 @@ var Builtins = map[string]*object.Builtin{
 	"max":       {Name: "max", Fn: Max},
 	"sorted":    {Name: "sorted", Fn: Sorted},
 	"reversed":  {Name: "reversed", Fn: Reversed},
+	"open":      {Name: "open", Fn: Open},
+	"close":     {Name: "close", Fn: Close},
+	"write":     {Name: "write", Fn: Write},
+	"read":      {Name: "read", Fn: Read},
+	"seek":      {Name: "seek", Fn: Seek},
 }
 
 // BuiltinsIndex ...
diff --git a/builtins/close.go b/builtins/close.go
new file mode 100644
index 0000000..94b6019
--- /dev/null
+++ b/builtins/close.go
@@ -0,0 +1,27 @@
+package builtins
+
+import (
+	"monkey/object"
+	"monkey/typing"
+	"syscall"
+)
+
+// Close  ...
+func Close(args ...object.Object) object.Object {
+	if err := typing.Check(
+		"close", args,
+		typing.ExactArgs(1),
+		typing.WithTypes(object.INTEGER_OBJ),
+	); err != nil {
+		return newError(err.Error())
+	}
+
+	fd := int(args[0].(*object.Integer).Value)
+
+	err := syscall.Close(syscall.Handle(fd))
+	if err != nil {
+		return newError("IOError: %s", err)
+	}
+
+	return &object.Null{}
+}
diff --git a/builtins/open.go b/builtins/open.go
new file mode 100644
index 0000000..125a21c
--- /dev/null
+++ b/builtins/open.go
@@ -0,0 +1,86 @@
+package builtins
+
+import (
+	"fmt"
+	"log"
+	"monkey/object"
+	"monkey/typing"
+	"os"
+	"syscall"
+)
+
+// Close  ...
+func parseMode(mode string) (int, error) {
+	var flag int
+	for _, c := range mode {
+		switch c {
+		case 'r':
+			if (flag & os.O_WRONLY) != 0 {
+				flag |= os.O_RDWR
+			} else {
+				log.Printf("r2")
+				flag |= os.O_RDONLY
+			}
+		case 'w':
+			if (flag & os.O_RDONLY) != 0 {
+				flag |= os.O_RDWR
+			} else {
+				flag |= os.O_WRONLY
+			}
+		case 'a':
+			flag |= os.O_APPEND
+		default:
+			return 0, fmt.Errorf("ValueError: mode string must be one of 'r', 'w', 'a', not '%c'", c)
+		}
+	}
+
+	if (flag&os.O_WRONLY) != 0 || (flag&os.O_RDWR) != 0 {
+		log.Printf("c1")
+		flag |= os.O_CREATE
+		if (flag & os.O_APPEND) == 0 {
+			log.Printf("t1")
+			flag |= os.O_TRUNC
+		}
+	}
+
+	if !((flag == os.O_RDONLY) || (flag&os.O_WRONLY != 0) || (flag&os.O_RDWR != 0)) {
+		return 0, fmt.Errorf("ValueError: mode string must be at least one of 'r', 'w', or 'rw'")
+	}
+
+	return flag, nil
+}
+
+// Open ...
+func Open(args ...object.Object) object.Object {
+	if err := typing.Check(
+		"open", args,
+		typing.RangeOfArgs(1, 2),
+		typing.WithTypes(object.STRING_OBJ, object.STRING_OBJ),
+	); err != nil {
+		return newError(err.Error())
+	}
+
+	var (
+		filename string
+		mode            = "r"
+		perm     uint32 = 0640
+	)
+
+	filename = args[0].(*object.String).Value
+
+	if len(args) == 2 {
+		mode = args[1].(*object.String).Value
+	}
+
+	flag, err := parseMode(mode)
+	if err != nil {
+		return newError(err.Error())
+	}
+
+	fd, err := syscall.Open(filename, flag, perm)
+	if err != nil {
+		return newError("IOError: %s", err)
+	}
+
+	return &object.Integer{Value: int64(fd)}
+}
diff --git a/builtins/read.go b/builtins/read.go
new file mode 100644
index 0000000..135f9aa
--- /dev/null
+++ b/builtins/read.go
@@ -0,0 +1,40 @@
+package builtins
+
+import (
+	"monkey/object"
+	"monkey/typing"
+	"syscall"
+)
+
+// DefaultBufferSize is the default buffer size
+const DefaultBufferSize = 4096
+
+// Read ...
+func Read(args ...object.Object) object.Object {
+	if err := typing.Check(
+		"read", args,
+		typing.RangeOfArgs(1, 2),
+		typing.WithTypes(object.INTEGER_OBJ, object.INTEGER_OBJ),
+	); err != nil {
+		return newError(err.Error())
+	}
+
+	var (
+		fd int
+		n  = DefaultBufferSize
+	)
+
+	fd = int(args[0].(*object.Integer).Value)
+
+	if len(args) == 2 {
+		n = int(args[1].(*object.Integer).Value)
+	}
+
+	buf := make([]byte, n)
+	n, err := syscall.Read(syscall.Handle(fd), buf)
+	if err != nil {
+		return newError("IOError: %s", err)
+	}
+
+	return &object.String{Value: string(buf[:n])}
+}
diff --git a/builtins/seek.go b/builtins/seek.go
new file mode 100644
index 0000000..e9b85d3
--- /dev/null
+++ b/builtins/seek.go
@@ -0,0 +1,37 @@
+package builtins
+
+import (
+	"monkey/object"
+	"monkey/typing"
+	"syscall"
+)
+
+// Seek ...
+func Seek(args ...object.Object) object.Object {
+	if err := typing.Check(
+		"seek", args,
+		typing.RangeOfArgs(1, 3),
+		typing.WithTypes(object.INTEGER_OBJ, object.INTEGER_OBJ, object.INTEGER_OBJ),
+	); err != nil {
+		return newError(err.Error())
+	}
+
+	var (
+		fd     int
+		whence = 0
+	)
+
+	fd = int(args[0].(*object.Integer).Value)
+	offset := args[1].(*object.Integer).Value
+
+	if len(args) == 3 {
+		whence = int(args[2].(*object.Integer).Value)
+	}
+
+	offset, err := syscall.Seek(syscall.Handle(fd), offset, whence)
+	if err != nil {
+		return newError("IOError: %s", err)
+	}
+
+	return &object.Integer{Value: offset}
+}
diff --git a/builtins/write.go b/builtins/write.go
new file mode 100644
index 0000000..47772c3
--- /dev/null
+++ b/builtins/write.go
@@ -0,0 +1,28 @@
+package builtins
+
+import (
+	"monkey/object"
+	"monkey/typing"
+	"syscall"
+)
+
+// Write ...
+func Write(args ...object.Object) object.Object {
+	if err := typing.Check(
+		"write", args,
+		typing.ExactArgs(2),
+		typing.WithTypes(object.INTEGER_OBJ, object.INTEGER_OBJ),
+	); err != nil {
+		return newError(err.Error())
+	}
+
+	fd := int(args[0].(*object.Integer).Value)
+	data := []byte(args[1].(*object.String).Value)
+
+	n, err := syscall.Write(syscall.Handle(fd), data)
+	if err != nil {
+		return newError("IOError: %s", err)
+	}
+
+	return &object.Integer{Value: int64(n)}
+}
diff --git a/compiler/compiler_test.go b/compiler/compiler_test.go
index cb12c27..cbdb16e 100644
--- a/compiler/compiler_test.go
+++ b/compiler/compiler_test.go
@@ -899,11 +899,11 @@ func TestBuiltins(t *testing.T) {
             `,
 			expectedConstants: []interface{}{1},
 			expectedInstructions: []code.Instructions{
-				code.Make(code.OpGetBuiltin, 18),
+				code.Make(code.OpGetBuiltin, 19),
 				code.Make(code.OpArray, 0),
 				code.Make(code.OpCall, 1),
 				code.Make(code.OpPop),
-				code.Make(code.OpGetBuiltin, 27),
+				code.Make(code.OpGetBuiltin, 29),
 				code.Make(code.OpArray, 0),
 				code.Make(code.OpConstant, 0),
 				code.Make(code.OpCall, 2),
@@ -914,7 +914,7 @@ func TestBuiltins(t *testing.T) {
 			input: `fn() { return len([]) }`,
 			expectedConstants: []interface{}{
 				[]code.Instructions{
-					code.Make(code.OpGetBuiltin, 18),
+					code.Make(code.OpGetBuiltin, 19),
 					code.Make(code.OpArray, 0),
 					code.Make(code.OpCall, 1),
 					code.Make(code.OpReturn),