diff --git a/os/src/fs/mod.rs b/os/src/fs/mod.rs
new file mode 100644
index 00000000..e481a78f
--- /dev/null
+++ b/os/src/fs/mod.rs
@@ -0,0 +1,20 @@
+mod pipe;
+mod stdio;
+
+use crate::mm::UserBuffer;
+use core::any::Any;
+
+pub trait File : Any + Send + Sync {
+    fn read(&self, buf: UserBuffer) -> usize;
+    fn write(&self, buf: UserBuffer) -> usize;
+    fn as_any_ref(&self) -> &dyn Any;
+}
+
+impl dyn File {
+    pub fn downcast_ref<T: File>(&self) -> Option<&T> {
+        self.as_any_ref().downcast_ref::<T>()
+    }
+}
+
+pub use pipe::{Pipe};
+pub use stdio::{Stdin, Stdout};
\ No newline at end of file
diff --git a/os/src/fs/pipe.rs b/os/src/fs/pipe.rs
new file mode 100644
index 00000000..266c43a0
--- /dev/null
+++ b/os/src/fs/pipe.rs
@@ -0,0 +1,167 @@
+use super::File;
+use alloc::sync::{Arc, Weak};
+use spin::Mutex;
+use crate::mm::{
+    UserBuffer,
+};
+use crate::task::suspend_current_and_run_next;
+use core::any::Any;
+
+pub struct Pipe {
+    readable: bool,
+    writable: bool,
+    buffer: Arc<Mutex<PipeRingBuffer>>,
+}
+
+impl Pipe {
+    pub fn read_end_with_buffer(buffer: Arc<Mutex<PipeRingBuffer>>) -> Self {
+        Self {
+            readable: true,
+            writable: false,
+            buffer,
+        }
+    }
+    pub fn write_end_with_buffer(buffer: Arc<Mutex<PipeRingBuffer>>) -> Self {
+        Self {
+            readable: false,
+            writable: true,
+            buffer,
+        }
+    }
+}
+
+const RING_BUFFER_SIZE: usize = 32;
+
+#[derive(Copy, Clone, PartialEq)]
+enum RingBufferStatus {
+    FULL,
+    EMPTY,
+    NORMAL,
+}
+
+pub struct PipeRingBuffer {
+    arr: [u8; RING_BUFFER_SIZE],
+    head: usize,
+    tail: usize,
+    status: RingBufferStatus,
+    write_end: Option<Weak<Mutex<Pipe>>>,
+}
+
+impl PipeRingBuffer {
+    pub fn new() -> Self {
+        Self {
+            arr: [0; RING_BUFFER_SIZE],
+            head: 0,
+            tail: 0,
+            status: RingBufferStatus::EMPTY,
+            write_end: None,
+        }
+    }
+    pub fn set_write_end(&mut self, write_end: &Arc<Mutex<Pipe>>) {
+        self.write_end = Some(Arc::downgrade(write_end));
+    }
+    pub fn write_byte(&mut self, byte: u8) {
+        self.status = RingBufferStatus::NORMAL;
+        self.arr[self.tail] = byte;
+        self.tail = (self.tail + 1) % RING_BUFFER_SIZE;
+        if self.tail == self.head {
+            self.status = RingBufferStatus::FULL;
+        }
+    }
+    pub fn read_byte(&mut self) -> u8 {
+        self.status = RingBufferStatus::NORMAL;
+        let c = self.arr[self.head];
+        self.head = (self.head + 1) % RING_BUFFER_SIZE;
+        if self.head == self.tail {
+            self.status = RingBufferStatus::EMPTY;
+        }
+        c
+    }
+    pub fn available_read(&self) -> usize {
+        if self.status == RingBufferStatus::EMPTY {
+            0
+        } else {
+            if self.tail > self.head {
+                self.tail - self.head
+            } else {
+                self.tail + RING_BUFFER_SIZE - self.head
+            }
+        }
+    }
+    pub fn available_write(&self) -> usize {
+        if self.status == RingBufferStatus::FULL {
+            0
+        } else {
+            RING_BUFFER_SIZE - self.available_read()
+        }
+    }
+    pub fn all_write_ends_closed(&self) -> bool {
+        self.write_end.as_ref().unwrap().upgrade().is_none()
+    }
+}
+
+/// Return (read_end, write_end)
+pub fn make_pipe() -> (Arc<Mutex<Pipe>>, Arc<Mutex<Pipe>>) {
+    let buffer = Arc::new(Mutex::new(PipeRingBuffer::new()));
+    let read_end = Arc::new(Mutex::new(
+        Pipe::read_end_with_buffer(buffer.clone())
+    ));
+    let write_end = Arc::new(Mutex::new(
+        Pipe::write_end_with_buffer(buffer.clone())
+    ));
+    buffer.lock().set_write_end(&write_end);
+    (read_end, write_end)
+}
+
+impl File for Pipe {
+    fn read(&self, buf: UserBuffer) -> usize {
+        assert_eq!(self.readable, true);
+        let mut buf_iter = buf.into_iter();
+        let mut read_size = 0usize;
+        loop {
+            let mut ring_buffer = self.buffer.lock();
+            let loop_read = ring_buffer.available_read();
+            if loop_read == 0 {
+                if ring_buffer.all_write_ends_closed() {
+                    return read_size;
+                }
+                drop(ring_buffer);
+                suspend_current_and_run_next();
+                continue;
+            }
+            // read at most loop_read bytes
+            for _ in 0..loop_read {
+                if let Some(byte_ref) = buf_iter.next() {
+                    unsafe { *byte_ref = ring_buffer.read_byte(); }
+                    read_size += 1;
+                } else {
+                    return read_size;
+                }
+            }
+        }
+    }
+    fn write(&self, buf: UserBuffer) -> usize {
+        assert_eq!(self.writable, true);
+        let mut buf_iter = buf.into_iter();
+        let mut write_size = 0usize;
+        loop {
+            let mut ring_buffer = self.buffer.lock();
+            let loop_write = ring_buffer.available_write();
+            if loop_write == 0 {
+                drop(ring_buffer);
+                suspend_current_and_run_next();
+                continue;
+            }
+            // write at most loop_write bytes
+            for _ in 0..loop_write {
+                if let Some(byte_ref) = buf_iter.next() {
+                    ring_buffer.write_byte(unsafe { *byte_ref });
+                    write_size += 1;
+                } else {
+                    return write_size;
+                }
+            }
+        }
+    }
+    fn as_any_ref(&self) -> &dyn Any { self }
+}
\ No newline at end of file
diff --git a/os/src/fs/stdio.rs b/os/src/fs/stdio.rs
new file mode 100644
index 00000000..4854118b
--- /dev/null
+++ b/os/src/fs/stdio.rs
@@ -0,0 +1,46 @@
+use super::File;
+use crate::mm::{UserBuffer, UserBufferIterator};
+use crate::sbi::console_getchar;
+use crate::task::suspend_current_and_run_next;
+use core::any::Any;
+
+pub struct Stdin;
+
+pub struct Stdout;
+
+impl File for Stdin {
+    fn read(&self, mut user_buf: UserBuffer) -> usize {
+        assert_eq!(user_buf.len(), 1);
+        // busy loop
+        let mut c: usize;
+        loop {
+            c = console_getchar();
+            if c == 0 {
+                suspend_current_and_run_next();
+                continue;
+            } else {
+                break;
+            }
+        }
+        let ch = c as u8;
+        unsafe { user_buf.buffers[0].as_mut_ptr().write_volatile(ch); }
+        1
+    }
+    fn write(&self, _user_buf: UserBuffer) -> usize {
+        panic!("Cannot write to stdin!");
+    }
+    fn as_any_ref(&self) -> &dyn Any { self }
+}
+
+impl File for Stdout {
+    fn read(&self, _user_buf: UserBuffer) -> usize{
+        panic!("Cannot read from stdout!");
+    }
+    fn write(&self, user_buf: UserBuffer) -> usize {
+        for buffer in user_buf.buffers.iter() {
+            print!("{}", core::str::from_utf8(*buffer).unwrap());
+        }
+        user_buf.len()
+    }
+    fn as_any_ref(&self) -> &dyn Any { self }
+}
\ No newline at end of file
diff --git a/os/src/main.rs b/os/src/main.rs
index aa21a5e2..02ebaeb2 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -22,6 +22,7 @@ mod config;
 mod task;
 mod timer;
 mod mm;
+mod fs;
 
 global_asm!(include_str!("entry.asm"));
 global_asm!(include_str!("link_app.S"));
diff --git a/os/src/mm/mod.rs b/os/src/mm/mod.rs
index cdf71da1..350b4fad 100644
--- a/os/src/mm/mod.rs
+++ b/os/src/mm/mod.rs
@@ -13,6 +13,8 @@ pub use page_table::{
     translated_byte_buffer,
     translated_str,
     translated_refmut,
+    UserBuffer,
+    UserBufferIterator,
 };
 pub use memory_set::{MemorySet, KERNEL_SPACE, MapPermission};
 pub use memory_set::remap_test;
diff --git a/os/src/mm/page_table.rs b/os/src/mm/page_table.rs
index 3c2f7f6f..93364e18 100644
--- a/os/src/mm/page_table.rs
+++ b/os/src/mm/page_table.rs
@@ -138,9 +138,7 @@ impl PageTable {
     pub fn translate_va(&self, va: VirtAddr) -> Option<PhysAddr> {
         self.find_pte(va.clone().floor())
             .map(|pte| {
-                //println!("translate_va:va = {:?}", va);
                 let aligned_pa: PhysAddr = pte.ppn().into();
-                //println!("translate_va:pa_align = {:?}", aligned_pa);
                 let offset = va.page_offset();
                 let aligned_pa_usize: usize = aligned_pa.into();
                 (aligned_pa_usize + offset).into()
@@ -189,9 +187,60 @@ pub fn translated_str(token: usize, ptr: *const u8) -> String {
 }
 
 pub fn translated_refmut<T>(token: usize, ptr: *mut T) -> &'static mut T {
-    //println!("into translated_refmut!");
     let page_table = PageTable::from_token(token);
     let va = ptr as usize;
-    //println!("translated_refmut: before translate_va");
     page_table.translate_va(VirtAddr::from(va)).unwrap().get_mut()
+}
+
+pub struct UserBuffer {
+    pub buffers: Vec<&'static mut [u8]>,
+}
+
+impl UserBuffer {
+    pub fn new(buffers: Vec<&'static mut [u8]>) -> Self {
+        Self { buffers }
+    }
+    pub fn len(&self) -> usize {
+        let mut total: usize = 0;
+        for b in self.buffers.iter() {
+            total += b.len();
+        }
+        total
+    }
+}
+
+impl IntoIterator for UserBuffer {
+    type Item = *mut u8;
+    type IntoIter = UserBufferIterator;
+    fn into_iter(self) -> Self::IntoIter {
+        UserBufferIterator {
+            buffers: self.buffers,
+            current_buffer: 0,
+            current_idx: 0,
+        }
+    }
+}
+
+pub struct UserBufferIterator {
+    buffers: Vec<&'static mut [u8]>,
+    current_buffer: usize,
+    current_idx: usize,
+}
+
+impl Iterator for UserBufferIterator {
+    type Item = *mut u8;
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.current_buffer >= self.buffers.len() {
+            None
+        } else {
+            let r = &mut self.buffers[self.current_buffer][self.current_idx] as *mut _;
+            if self.current_idx + 1 == self.buffers[self.current_buffer].len() {
+                self.current_idx = 0;
+                self.current_buffer += 1;
+            } else {
+                self.current_idx += 1;
+            }
+            Some(r)
+        }
+    }
 }
\ No newline at end of file
diff --git a/os/src/syscall/fs.rs b/os/src/syscall/fs.rs
index a10b53e9..1192af17 100644
--- a/os/src/syscall/fs.rs
+++ b/os/src/syscall/fs.rs
@@ -1,46 +1,40 @@
-use crate::mm::translated_byte_buffer;
-use crate::task::{current_user_token, suspend_current_and_run_next};
-use crate::sbi::console_getchar;
-
-const FD_STDIN: usize = 0;
-const FD_STDOUT: usize = 1;
+use crate::mm::{UserBuffer, translated_byte_buffer};
+use crate::task::{current_user_token, current_task};
 
 pub fn sys_write(fd: usize, buf: *const u8, len: usize) -> isize {
-    match fd {
-        FD_STDOUT => {
-            let buffers = translated_byte_buffer(current_user_token(), buf, len);
-            for buffer in buffers {
-                print!("{}", core::str::from_utf8(buffer).unwrap());
-            }
-            len as isize
-        },
-        _ => {
-            panic!("Unsupported fd in sys_write!");
-        }
+    let token = current_user_token();
+    let task = current_task().unwrap();
+    let inner = task.acquire_inner_lock();
+    if fd >= inner.fd_table.len() {
+        return -1;
+    }
+    if let Some(file) = &inner.fd_table[fd] {
+        let file = file.clone();
+        // release Task lock manually to avoid deadlock
+        drop(inner);
+        file.write(UserBuffer {
+            buffers: translated_byte_buffer(token, buf, len),
+        }) as isize
+    } else {
+        -1
     }
 }
 
 pub fn sys_read(fd: usize, buf: *const u8, len: usize) -> isize {
-    match fd {
-        FD_STDIN => {
-            assert_eq!(len, 1, "Only support len = 1 in sys_read!");
-            let mut c: usize;
-            loop {
-                c = console_getchar();
-                if c == 0 {
-                    suspend_current_and_run_next();
-                    continue;
-                } else {
-                    break;
-                }
-            }
-            let ch = c as u8;
-            let mut buffers = translated_byte_buffer(current_user_token(), buf, len);
-            unsafe { buffers[0].as_mut_ptr().write_volatile(ch); }
-            1
-        }
-        _ => {
-            panic!("Unsupported fd in sys_read!");
-        }
+    let token = current_user_token();
+    let task = current_task().unwrap();
+    let inner = task.acquire_inner_lock();
+    if fd >= inner.fd_table.len() {
+        return -1;
+    }
+    if let Some(file) = &inner.fd_table[fd] {
+        let file = file.clone();
+        // release Task lock manually to avoid deadlock
+        drop(inner);
+        file.read(UserBuffer {
+            buffers: translated_byte_buffer(token, buf, len),
+        }) as isize
+    } else {
+        -1
     }
 }
\ No newline at end of file
diff --git a/os/src/task/task.rs b/os/src/task/task.rs
index 21131736..e1be05a4 100644
--- a/os/src/task/task.rs
+++ b/os/src/task/task.rs
@@ -4,8 +4,10 @@ use crate::config::{TRAP_CONTEXT};
 use super::TaskContext;
 use super::{PidHandle, pid_alloc, KernelStack};
 use alloc::sync::{Weak, Arc};
+use alloc::vec;
 use alloc::vec::Vec;
 use spin::{Mutex, MutexGuard};
+use crate::fs::{File, Stdin, Stdout};
 
 pub struct TaskControlBlock {
     // immutable
@@ -24,6 +26,7 @@ pub struct TaskControlBlockInner {
     pub parent: Option<Weak<TaskControlBlock>>,
     pub children: Vec<Arc<TaskControlBlock>>,
     pub exit_code: i32,
+    pub fd_table: Vec<Option<Arc<dyn File + Send + Sync>>>,
 }
 
 impl TaskControlBlockInner {
@@ -74,6 +77,10 @@ impl TaskControlBlock {
                 parent: None,
                 children: Vec::new(),
                 exit_code: 0,
+                fd_table: vec![
+                    Some(Arc::new(Stdin)),
+                    Some(Arc::new(Stdout)),
+                ],
             }),
         };
         // prepare TrapContext in user space
@@ -136,6 +143,15 @@ impl TaskControlBlock {
         let kernel_stack_top = kernel_stack.get_top();
         // push a goto_trap_return task_cx on the top of kernel stack
         let task_cx_ptr = kernel_stack.push_on_top(TaskContext::goto_trap_return());
+        // copy fd table
+        let mut new_fd_table: Vec<Option<Arc<dyn File + Send + Sync>>> = Vec::new();
+        for fd in parent_inner.fd_table.iter() {
+            if let Some(file) = fd {
+                new_fd_table.push(Some(file.clone()));
+            } else {
+                new_fd_table.push(None);
+            }
+        }
         let task_control_block = Arc::new(TaskControlBlock {
             pid: pid_handle,
             kernel_stack,
@@ -148,6 +164,7 @@ impl TaskControlBlock {
                 parent: Some(Arc::downgrade(self)),
                 children: Vec::new(),
                 exit_code: 0,
+                fd_table: new_fd_table,
             }),
         });
         // add child