diff --git a/os/src/link_app.S b/os/src/link_app.S
index f80d18c..530389b 100644
--- a/os/src/link_app.S
+++ b/os/src/link_app.S
@@ -3,9 +3,13 @@
     .section .data
     .global _num_app
 _num_app:
-    .quad 1
+    .quad 5
     .quad app_0_start
-    .quad app_0_end
+    .quad app_1_start
+    .quad app_2_start
+    .quad app_3_start
+    .quad app_4_start
+    .quad app_4_end
 
     .section .data
     .global app_0_start
@@ -14,3 +18,35 @@ _num_app:
 app_0_start:
     .incbin "../user/target/riscv64gc-unknown-none-elf/release/hello"
 app_0_end:
+
+    .section .data
+    .global app_1_start
+    .global app_1_end
+    .align 3
+app_1_start:
+    .incbin "../user/target/riscv64gc-unknown-none-elf/release/power_3"
+app_1_end:
+
+    .section .data
+    .global app_2_start
+    .global app_2_end
+    .align 3
+app_2_start:
+    .incbin "../user/target/riscv64gc-unknown-none-elf/release/power_5"
+app_2_end:
+
+    .section .data
+    .global app_3_start
+    .global app_3_end
+    .align 3
+app_3_start:
+    .incbin "../user/target/riscv64gc-unknown-none-elf/release/power_7"
+app_3_end:
+
+    .section .data
+    .global app_4_start
+    .global app_4_end
+    .align 3
+app_4_start:
+    .incbin "../user/target/riscv64gc-unknown-none-elf/release/sleep"
+app_4_end:
diff --git a/user/src/bin/power_3.rs b/user/src/bin/power_3.rs
new file mode 100644
index 0000000..bcf9670
--- /dev/null
+++ b/user/src/bin/power_3.rs
@@ -0,0 +1,29 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user;
+
+const LEN: usize = 100;
+
+static mut S: [u64; LEN] = [0u64; LEN];
+
+#[no_mangle]
+unsafe fn main() -> i32 {
+    let p = 3u64;
+    let m = 998244353u64;
+    let iter: usize = 300000;
+    let mut cur = 0usize;
+    S[cur] = 1;
+    for i in 1..=iter {
+        let next = if cur + 1 == LEN { 0 } else { cur + 1 };
+        S[next] = S[cur] * p % m;
+        cur = next;
+        if i % 10000 == 0 {
+            println!("power_3 [{}/{}]", i, iter);
+        }
+    }
+    println!("{}^{} = {}(mod {})", p, iter, S[cur], m);
+    println!("Test power_3 OK!");
+    0
+}
\ No newline at end of file
diff --git a/user/src/bin/power_5.rs b/user/src/bin/power_5.rs
new file mode 100644
index 0000000..aba4029
--- /dev/null
+++ b/user/src/bin/power_5.rs
@@ -0,0 +1,29 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user;
+
+const LEN: usize = 100;
+
+static mut S: [u64; LEN] = [0u64; LEN];
+
+#[no_mangle]
+unsafe fn main() -> i32 {
+    let p = 5u64;
+    let m = 998244353u64;
+    let iter: usize = 210000;
+    let mut cur = 0usize;
+    S[cur] = 1;
+    for i in 1..=iter {
+        let next = if cur + 1 == LEN { 0 } else { cur + 1 };
+        S[next] = S[cur] * p % m;
+        cur = next;
+        if i % 10000 == 0 {
+            println!("power_5 [{}/{}]", i, iter);
+        }
+    }
+    println!("{}^{} = {}(mod {})", p, iter, S[cur], m);
+    println!("Test power_5 OK!");
+    0
+}
diff --git a/user/src/bin/power_7.rs b/user/src/bin/power_7.rs
new file mode 100644
index 0000000..3274daf
--- /dev/null
+++ b/user/src/bin/power_7.rs
@@ -0,0 +1,29 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user;
+
+const LEN: usize = 100;
+
+static mut S: [u64; LEN] = [0u64; LEN];
+
+#[no_mangle]
+unsafe fn main() -> i32 {
+    let p = 7u64;
+    let m = 998244353u64;
+    let iter: usize = 240000;
+    let mut cur = 0usize;
+    S[cur] = 1;
+    for i in 1..=iter {
+        let next = if cur + 1 == LEN { 0 } else { cur + 1 };
+        S[next] = S[cur] * p % m;
+        cur = next;
+        if i % 10000 == 0 {
+            println!("power_7 [{}/{}]", i, iter);
+        }
+    }
+    println!("{}^{} = {}(mod {})", p, iter, S[cur], m);
+    println!("Test power_7 OK!");
+    0
+}
diff --git a/user/src/bin/sleep.rs b/user/src/bin/sleep.rs
new file mode 100644
index 0000000..9fccd24
--- /dev/null
+++ b/user/src/bin/sleep.rs
@@ -0,0 +1,17 @@
+#![no_std]
+#![no_main]
+#[macro_use]
+extern crate user;
+
+use user::{get_time, yield_};
+
+#[no_mangle]
+fn main() -> i32 {
+    let current_timer = get_time();
+    let wait_for = current_timer + 3000;
+    while get_time() < wait_for {
+        yield_();
+    }
+    println!("Test sleep OK!");
+    0
+}
\ No newline at end of file
diff --git a/user/src/lib.rs b/user/src/lib.rs
index 29c7c38..9102c0b 100644
--- a/user/src/lib.rs
+++ b/user/src/lib.rs
@@ -2,7 +2,7 @@
 #![feature(asm)]
 #![feature(linkage)]
 
-use scall_os::{sys_exit, sys_write};
+use scall_os::*;
 
 #[macro_use]
 pub mod console;
@@ -23,4 +23,6 @@ fn main() -> i32 {
 }
 
 pub fn write(fd: usize, buf: &[u8]) -> isize { sys_write(fd, buf) }
-pub fn exit(exit_code: i32) -> isize { sys_exit(exit_code) }
\ No newline at end of file
+pub fn exit(exit_code: i32) -> isize { sys_exit(exit_code) }
+pub fn yield_() -> isize { sys_yield() }
+pub fn get_time() -> isize { sys_get_time() }
\ No newline at end of file
diff --git a/user/src/scall_os.rs b/user/src/scall_os.rs
index 02615f5..ee05a6d 100644
--- a/user/src/scall_os.rs
+++ b/user/src/scall_os.rs
@@ -1,5 +1,7 @@
 const SYSCALL_WRITE: usize = 64;
 const SYSCALL_EXIT: usize = 93;
+const SYSCALL_YIELD: usize = 124;
+const SYSCALL_GET_TIME: usize = 169;
 
 fn syscall(which: usize, args: [usize; 3]) -> isize {
     let mut ret;
@@ -23,3 +25,11 @@ pub fn sys_write(fd: usize, buffer: &[u8]) -> isize {
 pub fn sys_exit(exit_code: i32) -> isize {
     syscall(SYSCALL_EXIT, [exit_code as usize, 0, 0])
 }
+
+pub fn sys_yield() -> isize {
+    syscall(SYSCALL_YIELD, [0, 0, 0])
+}
+
+pub fn sys_get_time() -> isize {
+    syscall(SYSCALL_GET_TIME, [0, 0, 0])
+}