diff --git a/os/build.rs b/os/build.rs
index 925ec8af..a358a266 100644
--- a/os/build.rs
+++ b/os/build.rs
@@ -20,13 +20,30 @@ fn insert_app_data() -> Result<()> {
         })
         .collect();
 
+    writeln!(f, r#"
+    .align 4
+    .section .data
+    .global _num_app
+_num_app:
+    .quad {}
+    "#, apps.len())?;
+
+    for i in 0..apps.len() {
+        writeln!(f, r#"
+    .quad app_{}_start
+        "#, i)?;
+    }
+    writeln!(f, r#"
+    .quad app_{}_end
+    "#, apps.len() - 1)?;
+
     for (idx, app_with_extension) in apps.iter().enumerate() {
         writeln!(f, r#"
     .section .data
     .global app_{0}_start
     .global app_{0}_end
 app_{0}_start:
-    .incbin "{2}{1}"
+    .incbin "{2}{1}.bin"
 app_{0}_end:
         "#, idx, app_with_extension, TARGET_PATH)?;
     }
diff --git a/os/src/main.rs b/os/src/main.rs
index 6ec3f173..d571e81f 100644
--- a/os/src/main.rs
+++ b/os/src/main.rs
@@ -26,12 +26,19 @@ fn clear_bss() {
 
 #[no_mangle]
 pub fn rust_main() -> ! {
-    extern "C" {
-        fn app_0_start();
-        fn app_0_end();
-    };
     clear_bss();
     println!("Hello, world!");
-    println!("app_0 [{:#x}, {:#x})", app_0_start as usize, app_0_end as usize);
+    extern "C" {
+        fn _num_app();
+    }
+    let num_app_ptr = _num_app as usize as *const usize;
+    let num_app = unsafe { num_app_ptr.read_volatile() };
+    println!("num_app = {}", num_app);
+    let app_start: &[usize] = unsafe {
+        core::slice::from_raw_parts(num_app_ptr.add(1), num_app + 1)
+    };
+    for i in 0..num_app {
+        println!("app_{} [{:#x}, {:#x})", i, app_start[i], app_start[i + 1]);
+    }
     panic!("Shutdown machine!");
 }
\ No newline at end of file
diff --git a/os/rust-toolchain b/rust-toolchain
similarity index 100%
rename from os/rust-toolchain
rename to rust-toolchain
diff --git a/user/Makefile b/user/Makefile
index 546a2859..ab508d9a 100644
--- a/user/Makefile
+++ b/user/Makefile
@@ -2,16 +2,20 @@ TARGET := riscv64gc-unknown-none-elf
 MODE := release
 APP_DIR := src/bin
 TARGET_DIR := target/$(TARGET)/$(MODE)
-ELFS := $(patsubst $(APP_DIR)/*.rs, $(TARGET_DIR)/*, $(wildcard $(APP_DIR)/*.rs))
-BINS := $(patsubst $(APP_DIR)/*.rs, $(TARGET_DIR)/*.bin, $(wildcard $(APP_DIR)/*.rs))
+APPS := $(wildcard $(APP_DIR)/*.rs)
+ELFS := $(patsubst $(APP_DIR)/%.rs, $(TARGET_DIR)/%, $(APPS))
+BINS := $(patsubst $(APP_DIR)/%.rs, $(TARGET_DIR)/%.bin, $(APPS))
 
 OBJDUMP := rust-objdump --arch-name=riscv64
 OBJCOPY := rust-objcopy --binary-architecture=riscv64
 
 elf:
 	@cargo build --release
+	@echo $(APPS)
+	@echo $(ELFS)
+	@echo $(BINS)
 
 binary: elf
-	$(foreach elf, $(ELFS), $(OBJCOPY) $(elf) --strip-all -O binary $(patsubst $(TARGET_DIR)/*, $(TARGET_DIR)/*.bin, $(elf)))
+	$(foreach elf, $(ELFS), $(OBJCOPY) $(elf) --strip-all -O binary $(patsubst $(TARGET_DIR)/%, $(TARGET_DIR)/%.bin, $(elf));)
 
 build: binary
diff --git a/user/src/bin/power.rs b/user/src/bin/power.rs
new file mode 100644
index 00000000..cc9cb32d
--- /dev/null
+++ b/user/src/bin/power.rs
@@ -0,0 +1,27 @@
+#![no_std]
+#![no_main]
+
+#[macro_use]
+extern crate user_lib;
+
+const SIZE: usize = 10;
+const P: u32 = 3;
+const STEP: usize = 10000000;
+const MOD: u32 = 10007;
+
+#[no_mangle]
+fn main() -> i32 {
+    let mut pow = [0u32; SIZE];
+    let mut index: usize = 0;
+    pow[index] = 1;
+    for i in 1..=STEP {
+        let last = pow[index];
+        index = (index + 1) % SIZE;
+        pow[index] = last * P % MOD;
+        if i % 10000 == 0 {
+            println!("{}^{}={}", P, i, pow[index]);
+        }
+    }
+    println!("Test power OK!");
+    0
+}
\ No newline at end of file