diff --git a/.gitignore b/.gitignore
index 64ee209..c74ddbd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 target/
-.vscode/
\ No newline at end of file
+.vscode/
+*.dat
\ No newline at end of file
diff --git a/src/compression.rs b/src/compression.rs
index bb76783..e413f6e 100644
--- a/src/compression.rs
+++ b/src/compression.rs
@@ -1,5 +1,5 @@
 use crate::huffman::{HuffmanLeafNode, HuffmanInternalNode, HuffmanNode};
-use std::collections::{BinaryHeap, HashMap};
+use std::{collections::{BinaryHeap, HashMap}, fs::File, io::{self, Write}};
 
 pub struct CompressionTool {
     input: String, // todo: should also support streams
@@ -12,7 +12,7 @@ impl CompressionTool {
         }
     }
 
-    pub fn compress(&mut self) -> Result<HuffmanNode, String> {
+    fn generate_frequency_map(&self) -> HashMap<char, i32> {
         let mut map: HashMap<char, i32> = HashMap::new();
 
         for ch in self.input.chars() {
@@ -20,12 +20,44 @@ impl CompressionTool {
             *counter += 1;
         }
 
+        map
+    }
+
+    // Method to write header with frequency map to the output file
+    fn write_header(&self, file: &mut File, frequency_map: HashMap<char, i32>) -> io::Result<()> {
+        // Write the number of unique characters (for future decoding)
+        let num_chars: u32 = frequency_map.len() as u32;
+        file.write_all(&num_chars.to_le_bytes())?;
+
+        // Write the frequency table to the file
+        for (ch, count) in frequency_map {
+            file.write_all(&ch.to_string().as_bytes())?;
+            file.write_all(&count.to_le_bytes())?;
+        }
+
+        // Write a delimiter to indicate the end of the header
+        file.write_all(&[0x00])?;
+
+        Ok(())
+    }
+
+    pub fn compress(&mut self, output_file: &str) -> Result<(), String> {
+        let mut file: File = File::create(output_file).map_err(|e| e.to_string())?;
+
+        let frequency_map: HashMap<char, i32> = self.generate_frequency_map();
+
+        self.write_header(&mut file, frequency_map.clone())
+            .map_err(|e| format!("Error writing header: {}", e))?;
+
+        
+
         let mut heap: BinaryHeap<HuffmanNode> = BinaryHeap::new();
-        for (ch, count) in map {
+        for (ch, count) in frequency_map {
             let leaf: HuffmanLeafNode = HuffmanLeafNode::new(count, ch);
             heap.push(HuffmanNode::Leaf(leaf));
         }
 
+        // Build the Huffman tree
         while heap.len() > 1 {
             // Pop the two nodes with the smallest frequencies
             let left: HuffmanNode = heap.pop().unwrap();
@@ -39,12 +71,33 @@ impl CompressionTool {
 
         let root = heap.pop().unwrap();
 
+        // Generate the prefix codes for each character
         let mut codes: HashMap<char, String> = HashMap::new();
         root.generate_prefix_codes(&mut codes);
-        for (ch, code) in &codes {
-            println!("Character: '{}' -> code: {}", ch, code);
+
+        // Now write the compressed data after the header
+        let compressed_data = self.compressed_data(&codes);
+        file.write_all(&compressed_data).map_err(|e| e.to_string())?;
+
+
+        Ok(())
+    }
+
+    fn compressed_data(&self, codes: &HashMap<char, String>) -> Vec<u8> {
+        let mut compressed_bits = String::new();
+        for ch in self.input.chars() {
+            compressed_bits.push_str(&codes[&ch]);
+        }
+
+        // Convert the binary string to byte vector
+        let mut result = Vec::new();
+        for chunk in compressed_bits.as_bytes().chunks(8) {
+            let byte = chunk.iter().fold(0, |acc, &bit| (acc <<1) | (bit - b'0') as u8);
+            result.push(byte);
         }
 
-        Ok(root)
+        result
     }
+
+
 }
diff --git a/src/main.rs b/src/main.rs
index bddd605..6720eae 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,19 +5,20 @@ use compression_tool::compression::CompressionTool;
 
 fn main() {
     let args: Vec<String> = std::env::args().collect();
-    let file_path: String = args[1].to_string();
+    if args.len() != 3 {
+        println!("Usage: cargo run <input_file> <output_file>");
+        return;
+    }
+    let input_file: &String = &args[1];
+    let output_file: &String = &args[2];
 
-    let mut file: File = File::open(file_path).unwrap();
-    
+    let mut file: File = File::open(input_file).unwrap();    
     let mut content: String = String::new();
     let _ = file.read_to_string(&mut content);
 
-    let mut tool = CompressionTool::new(&content);
-    match tool.compress() {
-        Ok(root) => {
-            root.print_tree();
-            println!("{:?}", root)
-        },
+    let mut tool: CompressionTool = CompressionTool::new(&content);
+    match tool.compress(&output_file) {
+        Ok(_) => println!("Compression successfull, file written to '{}'", output_file),
         Err(e) => println!("Error: {}", e),
     }
 }