diff --git a/implement-shell-tools/cat/cat-commander.js b/implement-shell-tools/cat/cat-commander.js
new file mode 100644
index 00000000..5cc5ffb2
--- /dev/null
+++ b/implement-shell-tools/cat/cat-commander.js
@@ -0,0 +1,56 @@
+import { program } from "commander";
+import { promises as fs } from "node:fs";
+import process from "node:process";
+
+program
+    .name("read-files-content")
+    .description("Read the content of a file (simulating cat command)")
+    .option("-n, --number","Number of lines")
+    .option("-b","Number of no-blanks lines")
+    .argument("<path...>","The file path to process"); //file
+
+program.parse();
+
+const argv = program.args;
+
+if (argv.length === 0) {
+    console.error(`Expected file path(s),passed but got ${argv.length}.`);
+    process.exit(1);
+}
+
+//const path = argv[0];
+for (const path of argv){
+    const option = program.opts();
+    const content = await fs.readFile(path, "utf-8");
+    if (option.number){
+        // split content
+        let lines = content.split(/\n/);
+        // removes last line
+        if (lines[lines.length - 1] === ""){
+            lines = lines.slice(0,-1);
+        }
+        lines
+            .map((line,index) => `${(index + 1).toString().padStart(6)}\t${line}`)
+            .forEach(line => console.log(line))
+
+        } else if (option.b){
+            let lines = content.split("\n");
+            let linesCounter = 0;
+            if (lines[lines.length - 1] === ""){
+                lines = lines.slice(0,-1);
+            }
+            lines
+            .map((line) => {
+                if (line.trim().length > 0) { 
+                    linesCounter++;
+                    return `${linesCounter.toString().padStart(6)}\t${line}`
+                }else{
+                    return `${line}`
+                    }}
+                )
+            .forEach(line => console.log(line))
+        }else {
+            const output = content.endsWith("\n") ? content.slice(0,-1) : content;
+            console.log(output);
+    }
+}
diff --git a/implement-shell-tools/ls/ls-commander.js b/implement-shell-tools/ls/ls-commander.js
new file mode 100644
index 00000000..9ca8c442
--- /dev/null
+++ b/implement-shell-tools/ls/ls-commander.js
@@ -0,0 +1,36 @@
+import { program } from "commander";
+import { promises as fs } from "node:fs";
+import process from "node:process";
+
+program 
+    .name("list-files")
+    .description("List files in a directory")
+    .option("-1", "Show line by line")
+    .option("-a, --all", "Show hidden files")
+    .argument("[paths...]", "The directory paths",["."]);
+
+program.parse();
+
+const argv = program.args;
+
+if (argv.length != 1){
+    console.error(`Expected exactly 1 argument (a path) to be passed but got ${argv.length}`);
+    process.exit(1);
+}
+const dirPath = argv[0];
+const options = program.opts();
+
+const entries = await fs.readdir(dirPath)
+
+const listFiles = entries.map((entry) => `${entry.padStart(6)}` )
+const noHidden = listFiles.filter(name => !name.startsWith('.'));
+
+if (options.all && options[1]){
+    console.log(listFiles.join('\n'));
+} else if (options.all) {
+    console.log(listFiles.join(' '));
+} else if (options[1]){
+    console.log(noHidden.join('\n'));
+} else {
+    console.log(noHidden.join(' '));
+}
diff --git a/implement-shell-tools/wc/wc-commander.js b/implement-shell-tools/wc/wc-commander.js
new file mode 100644
index 00000000..b1c28b2c
--- /dev/null
+++ b/implement-shell-tools/wc/wc-commander.js
@@ -0,0 +1,61 @@
+import {program} from "commander";
+import { promises as fs } from "node:fs";
+import process from "node:process";
+import { glob } from "glob";
+
+program
+    .name("content counter")
+    .description("Counts lines, words, or characters in a file or files of a directory.")
+    .option("-l,--lines","Options for l:Lines.")
+    .option("-w,--words","Options for w:words.")
+    .option("-c","Options for c:characters.")
+    .argument("<path...>","The file or directory to process");
+
+program.parse();
+
+const argv = program.args;
+
+const options = program.opts();
+
+const result = []; 
+let totalLines = 0;
+let totalWords = 0;
+let totalChars = 0;
+
+for (const file of argv){
+
+  //1.  Read each file
+
+  const content = await fs.readFile(file,"utf-8");
+  // 2. calculate values
+  const lines = content.split(/\n/g).length - 1 ;
+  const words = content.trim().split(/\s+/).length;
+  const chars = content.split("").length;
+  // variable to pile up final line results according options
+  const thisLine = [];
+  if (options.lines){ thisLine.push(lines.toString().padStart(8)) };
+  if (options.words){ thisLine.push(words.toString().padStart(8)) };
+  if (options.c){ thisLine.push(chars.toString().padStart(8)) };
+  if (!options.lines && !options.words && !options.c){ thisLine.push(lines.toString().padStart(8),words.toString().padStart(8),chars.toString().padStart(8)) };
+  result.push(`${thisLine.join("")} ${file}`)
+  // 3. add results 
+  // variables to accumulate the total
+  totalLines += lines;
+  totalWords += words;
+  totalChars += chars;
+// 4. add total results if several files
+}
+if (argv.length>1){
+  const finalLine = [];
+  finalLine.push(totalLines.toString().padStart(8)),
+  finalLine.push(totalWords.toString().padStart(8)),
+  finalLine.push(totalChars.toString().padStart(8));
+  result.push(`${finalLine.join("")} total`)
+}
+// 5. show results
+const output = result.join('\n');
+console.log(output)
+
+
+
+
diff --git a/number-systems/README.md b/number-systems/README.md
deleted file mode 100644
index 77a3bde9..00000000
--- a/number-systems/README.md
+++ /dev/null
@@ -1,65 +0,0 @@
-Do not use any tools or programming to solve these problems. Work it out yourself by hand, and fill in the answers.
-
-Do not convert any binary numbers to decimal when solving a question unless the question explicitly tells you to.
-
-The goal of these exercises is for you to gain an intuition for binary numbers. Using tools to solve the problems defeats the point.
-
-Convert the decimal number 14 to binary.
-Answer:
-
-Convert the binary number 101101 to decimal:
-Answer:
-
-Which is larger: 1000 or 0111?
-Answer:
-
-Which is larger: 00100 or 01011?
-Answer:
-
-What is 10101 + 01010?
-Answer:
-
-What is 10001 + 10001?
-Answer:
-
-What's the largest number you can store with 4 bits, if you want to be able to represent the number 0?
-Answer:
-
-How many bits would you need in order to store the numbers between 0 and 255 inclusive?
-Answer:
-
-How many bits would you need in order to store the numbers between 0 and 3 inclusive?
-Answer:
-
-How many bits would you need in order to store the numbers between 0 and 1000 inclusive?
-Answer:
-
-How can you test if a binary number is a power of two (e.g. 1, 2, 4, 8, 16, ...)?
-Answer:
-
-Convert the decimal number 14 to hex.
-Answer:
-
-Convert the decimal number 386 to hex.
-Answer:
-
-Convert the hex number 386 to decimal.
-Answer:
-
-Convert the hex number B to decimal.
-Answer:
-
-If reading the byte 0x21 as a number, what decimal number would it mean?
-Answer:
-
-If reading the byte 0x21 as an ASCII character, what character would it mean?
-Answer:
-
-If reading the byte 0x21 as a greyscale colour, as described in "Approaches for Representing Colors and Images", what colour would it mean?
-Answer:
-
-If reading the bytes 0xAA00FF as an RGB colour, as described in "Approaches for Representing Colors and Images", what colour would it mean?
-Answer:
-
-If reading the bytes 0xAA00FF as a sequence of three one-byte decimal numbers, what decimal numbers would they be?
-Answer: