diff --git a/wfassoc/src/components.rs b/wfassoc/src/components.rs
new file mode 100644
index 0000000..6738297
--- /dev/null
+++ b/wfassoc/src/components.rs
@@ -0,0 +1,41 @@
+/// The struct representing an Windows acceptable Prgram ID, 
+/// which looks like `Program.Document.2`
+pub struct ProgId {
+    inner: String,
+}
+
+impl ProgId {
+    pub fn new(prog_id: &str) -> Self {
+        Self {
+            inner: prog_id.to_string(),
+        }
+    }
+}
+
+/// Representing an file extension which must start with dot (`.`)
+/// and followed by arbitrary characters.
+pub struct FileExt {
+    inner: String,
+}
+
+impl FileExt {
+    pub fn new(file_ext: &str) -> Self {
+        Self {
+            inner: file_ext.to_string(),
+        }
+    }
+}
+
+/// Representing an Windows recognizable icon string with format like:
+/// `@path_to_file.exe,61`.
+pub struct WinRc {
+    inner: String,
+}
+
+impl WinRc {
+    pub fn new(icon: &str) -> Self {
+        Self {
+            inner: icon.to_string(),
+        }
+    }
+}
diff --git a/wfassoc/src/lib.rs b/wfassoc/src/lib.rs
index 006a715..b914ec9 100644
--- a/wfassoc/src/lib.rs
+++ b/wfassoc/src/lib.rs
@@ -1,6 +1,9 @@
 #[cfg(not(target_os = "windows"))]
 compile_error!("Crate wfassoc is only supported on Windows.");
 
+pub(crate) mod components;
+pub(crate) mod program;
+
 pub fn add(left: u64, right: u64) -> u64 {
     left + right
 }
diff --git a/wfassoc/src/program.rs b/wfassoc/src/program.rs
new file mode 100644
index 0000000..8670b0d
--- /dev/null
+++ b/wfassoc/src/program.rs
@@ -0,0 +1,17 @@
+use super::components::*;
+
+pub struct Program {
+    name: String,
+    prog_id: ProgId,
+    file_exts: Vec<FileExt>,
+}
+
+impl Program {
+    pub fn new() -> Self {
+        Self {
+            name: String::new(),
+            prog_id: ProgId::new(""),
+            file_exts: Vec::new(),
+        }
+    }
+}