diff --git a/wfassoc-exec/src/cli.rs b/wfassoc-exec/src/cli.rs
index 2b54e95..d260bc8 100644
--- a/wfassoc-exec/src/cli.rs
+++ b/wfassoc-exec/src/cli.rs
@@ -82,9 +82,9 @@ pub enum CliCommands {
     #[command(name = "status")]
     #[command(about = "Fetch the status of registration with given manifest and scope.")]
     Status {
-        /// The scope where fetch info.
-        #[arg(short = 't', long = "target", value_name = "TARGET", required = true, value_enum, default_value_t = RegScope::User)]
-        target: RegScope,
+        /// The view where fetch info.
+        #[arg(short = 't', long = "target", value_name = "TARGET", required = true, value_enum, default_value_t = RegView::User)]
+        target: RegView,
     },
     #[command(name = "ext")]
     #[command(about = "File extension related operations according to given program manifest.")]
diff --git a/wfassoc-exec/src/runner.rs b/wfassoc-exec/src/runner.rs
index 6272506..a6fe8ae 100644
--- a/wfassoc-exec/src/runner.rs
+++ b/wfassoc-exec/src/runner.rs
@@ -8,15 +8,18 @@ use thiserror::Error as TeError;
 /// Error occurs in this module.
 #[derive(Debug, TeError)]
 pub enum Error {
-    /// Error when parsing manifest TOML file.
+    /// Error when parsing Manifest TOML file.
     #[error("{0}")]
     ParseManifest(#[from] manifest::ParseManifestError),
-    /// Error when parsing manifest into schema.
+    /// Error when parsing Manifest into Schema.
     #[error("{0}")]
     ParseSchema(#[from] manifest::ParseSchemaError),
-    /// Error when parsing schema into program.
+    /// Error when parsing Schema into Program.
     #[error("{0}")]
     ParseProgram(#[from] wfassoc::highlevel::ParseProgramError),
+    /// Error when operating Program.
+    #[error("{0}")]
+    Program(#[from] wfassoc::highlevel::ProgramError),
 }
 
 /// Result type used in this module.
@@ -34,16 +37,22 @@ fn stringified_exts_to_indices(program: &wfassoc::Program, exts: Vec<String>) ->
 
 // region: Respective Runners
 
-fn run_register(program: wfassoc::Program, scope: wfassoc::Scope) -> Result<()> {
-    todo!()
+fn run_register(mut program: wfassoc::Program, scope: wfassoc::Scope) -> Result<()> {
+    Ok(program.register(scope)?)
 }
 
-fn run_unregister(program: wfassoc::Program, scope: wfassoc::Scope) -> Result<()> {
-    todo!()
+fn run_unregister(mut program: wfassoc::Program, scope: wfassoc::Scope) -> Result<()> {
+    Ok(program.unregister(scope)?)
 }
 
-fn run_status(program: wfassoc::Program, scope: wfassoc::Scope) -> Result<()> {
-    todo!()
+fn run_status(program: wfassoc::Program, view: wfassoc::View) -> Result<()> {
+    if program.is_registered(view)? {
+        println!("Application is installed.");
+    } else {
+        println!("Application is not installed.");
+    }
+    
+    Ok(())
 }
 
 fn run_ext_link(program: wfassoc::Program, scope: wfassoc::Scope, exts: Vec<String>) -> Result<()> {
diff --git a/wfassoc/src/highlevel.rs b/wfassoc/src/highlevel.rs
index 6df9bc9..eee0f43 100644
--- a/wfassoc/src/highlevel.rs
+++ b/wfassoc/src/highlevel.rs
@@ -167,17 +167,43 @@ pub struct Program {
 impl TryFrom<Schema> for Program {
     type Error = ParseProgramError;
 
-    fn try_from(value: Schema) -> std::result::Result<Self, Self::Error> {
+    fn try_from(value: Schema) -> Result<Self, Self::Error> {
         Self::new(value)
     }
 }
 
 impl Program {
+    /// Try creating Program from Schema.
     pub fn new(schema: Schema) -> Result<Self, ParseProgramError> {
         todo!()
     }
 }
 
+impl Program {
+    /// Register this application.
+    /// 
+    /// If there is registration of this application,
+    /// this function will return error.
+    pub fn register(&mut self, scope: Scope) -> Result<(), ProgramError> {
+        todo!()
+    }
+
+    /// Unregister this application.
+    /// 
+    /// If there is no registration of this application,
+    /// this function will return error.
+    pub fn unregister(&mut self, scope: Scope) -> Result<(), ProgramError> {
+        todo!()
+    }
+
+    /// Check whether this application has been registered in given view.
+    ///
+    /// Please note that this is a rough check and do not validate any data.
+    pub fn is_registered(&self, view: View) -> Result<bool, ProgramError> {
+        todo!()
+    }
+}
+
 // endregion
 
 // region: Program Internals