diff --git a/allocate_laptop.py b/allocate_laptop.py
new file mode 100644
index 000000000..3a842d9dc
--- /dev/null
+++ b/allocate_laptop.py
@@ -0,0 +1,91 @@
+from dataclasses import dataclass
+from enum import Enum
+from typing import List, Dict, Tuple, Optional
+
+class OperatingSystem(Enum):
+    MACOS = "macOS"
+    ARCH = "Arch Linux"
+    UBUNTU = "Ubuntu"
+
+@dataclass(frozen=True)
+class Person:
+    name: str
+    age: int
+    # Sorted in order of preference, most preferred is first.
+    preferred_operating_systems: List[OperatingSystem]
+
+
+@dataclass(frozen=True)
+class Laptop:
+    id: int
+    manufacturer: str
+    model: str
+    screen_size_in_inches: float
+    operating_system: OperatingSystem
+
+def norm_os_values(value: str) -> OperatingSystem:
+    value = value.strip().lower()
+    if value == "ubuntu":
+        return OperatingSystem.UBUNTU
+    if value == "arch linux":
+        return OperatingSystem.ARCH
+    if value == "macos":
+        return OperatingSystem.MACOS
+    raise ValueError(f"Unknown OS: {value}")
+
+
+people = [
+    Person(name="Imran", age=22, preferred_operating_systems=[norm_os_values("Ubuntu"), norm_os_values("Arch Linux")]),
+    Person(name="Eliza", age=34, preferred_operating_systems=[norm_os_values("Arch Linux"), norm_os_values("macOS"), norm_os_values("Ubuntu")]),
+    Person(name="Ira", age=21, preferred_operating_systems=[norm_os_values("Ubuntu"), norm_os_values("Arch Linux")]),
+    Person(name="Anna", age=34, preferred_operating_systems=[norm_os_values("Ubuntu"), norm_os_values("macOS")]),
+    Person(name="Nahimn", age=42, preferred_operating_systems=[norm_os_values("Ubuntu"), norm_os_values("Arch Linux")])
+]
+
+laptops = [
+    Laptop(id=1, manufacturer="Dell", model="XPS", screen_size_in_inches=13, operating_system=norm_os_values("Arch Linux")),
+    Laptop(id=2, manufacturer="Dell", model="XPS", screen_size_in_inches=15, operating_system=norm_os_values("Ubuntu")),
+    Laptop(id=3, manufacturer="Dell", model="XPS", screen_size_in_inches=15, operating_system=norm_os_values("ubuntu")),
+    Laptop(id=4, manufacturer="Apple", model="macBook", screen_size_in_inches=13, operating_system=norm_os_values("macOS")),
+]
+
+
+def allocate_laptops(people: List[Person], laptops: List[Laptop]) -> Dict[Tuple[str, int], int]:
+    sadness_table: Dict[Tuple[str, int], int] = {}
+    for person in people:
+        for laptop in laptops:
+            if laptop.operating_system in person.preferred_operating_systems:
+                index = person.preferred_operating_systems.index(laptop.operating_system)
+                sadness = index
+            else:
+                sadness = 100
+            sadness_table[(person.name, laptop.id)] = sadness
+    return sadness_table
+
+
+sadness_table = allocate_laptops(people, laptops)
+
+allocation_list: List[Tuple[str, Optional[int], int]] = []
+allocated_laptops: set[int] = set()
+allocated_persons: set[str] = set()
+total_happiness: int = 0
+
+for (person_name, laptop_id), sadness in sorted(sadness_table.items(), key=lambda value: value[1]):
+    if laptop_id in allocated_laptops:
+        continue
+    if person_name in allocated_persons:
+        continue
+    allocation_list.append((person_name, laptop_id, sadness))
+    allocated_laptops.add(laptop_id)
+    allocated_persons.add(person_name)
+    total_happiness += sadness
+    print(f"{person_name} got laptop {laptop_id}")
+
+    
+for person in people:
+    if person.name not in allocated_persons:
+        print(f"{person.name} did not get laptop")
+print(f"Total happiness: {total_happiness}")
+
+print(allocation_list)
+
diff --git a/implement-shell-tools/cat/cat.js b/implement-shell-tools/cat/cat.js
new file mode 100644
index 000000000..331be0929
--- /dev/null
+++ b/implement-shell-tools/cat/cat.js
@@ -0,0 +1,33 @@
+import process from "node:process";
+import { promises as fs } from "node:fs";
+
+const arrArgv = process.argv.slice(2);
+
+const numberLines = arrArgv.includes("-n");
+const numberNonemptyLines = arrArgv.includes("-b");
+
+const nonFlagArrArgv = arrArgv.filter((arr) => !arr.startsWith("-"));
+
+let number = 1;
+
+for (let file of nonFlagArrArgv) {
+  const content = await fs.readFile(file, "utf-8");
+
+  const linedText = content.split("\n");
+
+  const numbered = linedText.map((line) => {
+    if (numberNonemptyLines) {
+      if (line.trim() === "") {
+        return line;
+      } else {
+        return `${String(number++).padStart(3)}  ${line}`;
+      }
+    }
+    if (numberLines) {
+      return `${String(number++).padStart(3)}  ${line}`;
+    }
+
+    return line;
+  });
+  console.log(numbered.join("\n"));
+}
diff --git a/implement-shell-tools/ls/ls.js b/implement-shell-tools/ls/ls.js
new file mode 100644
index 000000000..47414da60
--- /dev/null
+++ b/implement-shell-tools/ls/ls.js
@@ -0,0 +1,56 @@
+import process from "node:process";
+import { promises as fs } from "node:fs";
+import path from "node:path";
+
+const arrArgv = process.argv.slice(2);
+
+const longFormat = arrArgv.includes("-l");
+const showHidden = arrArgv.includes("-a");
+
+const paths = arrArgv.filter((argv) => !argv.startsWith("-"));
+if (paths.length === 0) path = "[.]";
+
+for (let listFile of paths) {
+  const status = await fs.stat(listFile);
+
+  if (status.isFile()) {
+    const permissions = (status.mode & 0o777).toString(8);
+    const sizeFile = status.size;
+    const owner = status.uid;
+    const group = status.gid;
+    const timeMod = status.mtime.toLocaleString();
+
+    if (longFormat) {
+      console.log(
+        `${permissions}, ${owner}, ${group}, ${sizeFile}, ${timeMod}, ${listFile}`
+      );
+    } else {
+      console.log(listFile);
+    }
+  } else {
+    let files = await fs.readdir(listFile, { withFileTypes: true });
+
+    if (!showHidden) {
+      files = files.filter((file) => !file.name.startsWith("."));
+    }
+
+    for (let file of files) {
+      const wholePath = path.join(listFile, file.name);
+      const statusFile = await fs.stat(wholePath);
+
+      const permissions = (statusFile.mode & 0o777).toString(8);
+      const sizeFile = statusFile.size;
+      const owner = statusFile.uid;
+      const group = statusFile.gid;
+      const timeMod = statusFile.mtime.toLocaleString();
+
+      if (longFormat) {
+        console.log(
+          `${permissions}, ${owner}, ${group}, ${sizeFile}, ${timeMod}, ${file.name}`
+        );
+      } else {
+        console.log(file.name);
+      }
+    }
+  }
+}
diff --git a/implement-shell-tools/wc/wc.js b/implement-shell-tools/wc/wc.js
new file mode 100644
index 000000000..2648d62d3
--- /dev/null
+++ b/implement-shell-tools/wc/wc.js
@@ -0,0 +1,38 @@
+import process from "node:process";
+import { promises as fs } from "node:fs";
+
+const arrArgv = process.argv.slice(2);
+
+const lines = arrArgv.includes("-l");
+const words = arrArgv.includes("-w");
+const bytes = arrArgv.includes("-c");
+
+const noFlags = !lines && !words && !bytes;
+
+const paths = arrArgv.filter((argv) => !argv.startsWith("-"));
+
+for (let path of paths) {
+  const context = await fs.readFile(path, "utf-8");
+
+  const countLines = context.split(/\r?\n/).length;
+  const countWords = context.split(/\s+/).length;
+  const countBytes = Buffer.byteLength(context, "utf-8");
+
+  let startInput = "";
+
+  if (noFlags || lines) {
+    startInput += `${countLines} `;
+  }
+
+  if (noFlags || words) {
+    startInput += `${countWords} `;
+  }
+
+  if (noFlags || bytes) {
+    startInput += `${countBytes} `;
+  }
+
+  startInput += path;
+
+  console.log(startInput);
+}