diff --git a/module1.ipynb b/module1.ipynb
index 7665d18..2291ee3 100644
--- a/module1.ipynb
+++ b/module1.ipynb
@@ -518,7 +518,116 @@
   {
    "cell_type": "markdown",
    "metadata": {},
-   "source": []
+   "source": [
+    "# Study guide: diff and patch\n",
+    "\n",
+    "## The diff command\n",
+    "\n",
+    "You use the diff command to find the differences between two files. On its own, it’s a bit hard to use; instead, use diff -u to find lines that differ in two files:\n",
+    "\n",
+    "## Using diff -u\n",
+    "\n",
+    "You use the diff -u command to compare two files, line by line, and have the differing lines compared side-by-side in the same output. For an example of what this looks like, see below:\n",
+    "\n",
+    "```bash\n",
+    "~$ cat menu1.txt \n",
+    "\n",
+    "Menu1:\n",
+    "\n",
+    "Apples\n",
+    "\n",
+    "Bananas\n",
+    "\n",
+    "Oranges\n",
+    "\n",
+    "Pears\n",
+    "\n",
+    "~$ cat menu2.txt \n",
+    "\n",
+    "Menu:\n",
+    "\n",
+    "Apples\n",
+    "\n",
+    "Bananas\n",
+    "\n",
+    "Grapes\n",
+    "\n",
+    "Strawberries\n",
+    "\n",
+    "~$ diff \\-u menu1.txt menu2.txt \n",
+    "\n",
+    "\\--- menu1.txt   2019\\-12-16 18:46:13.794879924 +0900\n",
+    "\n",
+    "+++ menu2.txt   2019\\-12-16 18:46:42.090995670 +0900\n",
+    "\n",
+    "@@ \\-1,6 +1,6 @@\n",
+    "\n",
+    "\\-Menu1:\n",
+    "\n",
+    "+Menu:\n",
+    "\n",
+    " Apples\n",
+    "\n",
+    " Bananas\n",
+    "\n",
+    "\\-Oranges\n",
+    "\n",
+    "\\-Pears\n",
+    "\n",
+    "+Grapes\n",
+    "\n",
+    "+Strawberries\n",
+    "```\n",
+    "\n",
+    "## The patch command\n",
+    "\n",
+    "The patch command is useful for applying file differences. See the example below, which compares two files. The comparison is saved as a .diff file, which is then patched to the original file!\n",
+    "\n",
+    "```bash\n",
+    "~$ cat hello\\_world.txt \n",
+    "\n",
+    "Hello World\n",
+    "\n",
+    "~$ cat hello\\_world\\_long.txt \n",
+    "\n",
+    "Hello World\n",
+    "\n",
+    "It's a wonderful day!\n",
+    "\n",
+    "~$ diff -u hello\\_world.txt hello\\_world\\_long.txt \n",
+    "\n",
+    "\\--- hello\\_world.txt     2019-12-16 19:24:12.556102821 +0900\n",
+    "\n",
+    "+++ hello\\_world\\_long.txt        2019-12-16 19:24:38.944207773 +0900\n",
+    "\n",
+    "@@ -1 +1,3 @@\n",
+    "\n",
+    " Hello World\n",
+    "\n",
+    "+\n",
+    "\n",
+    "+It's a wonderful day!\n",
+    "\n",
+    "~$ diff \\-u hello\\_world.txt hello\\_world\\_long.txt > hello\\_world.diff\n",
+    "\n",
+    "~$ patch hello\\_world.txt < hello\\_world.diff \n",
+    "\n",
+    "patching file hello\\_world.txt\n",
+    "\n",
+    "~$ cat hello\\_world.txt \n",
+    "\n",
+    "Hello World\n",
+    "\n",
+    "It's a wonderful day!\n",
+    "```\n",
+    "\n",
+    "## Resources for more information\n",
+    "\n",
+    "There are other interesting patch and diff commands such as patch -p1 and diff -r . For more information on these commands, check out the following resources:\n",
+    "\n",
+    "- [http://man7.org/linux/man-pages/man1/diff.1.html<svg aria-labelledby=\"cds-react-aria8760104591-:rgs:-title\" fill=\"none\" focusable=\"false\" height=\"16\" role=\"img\" viewBox=\"0 0 20 20\" width=\"16\" class=\"css-8blerm\" id=\"cds-react-aria8760104591-:rgs:\"><title id=\"cds-react-aria8760104591-:rgs:-title\">Opens in a new tab</title></svg>](http://man7.org/linux/man-pages/man1/diff.1.html)\n",
+    "- [http://man7.org/linux/man-pages/man1/patch.1.html<svg aria-labelledby=\"cds-react-aria8760104591-:rgu:-title\" fill=\"none\" focusable=\"false\" height=\"16\" role=\"img\" viewBox=\"0 0 20 20\" width=\"16\" class=\"css-8blerm\" id=\"cds-react-aria8760104591-:rgu:\"><title id=\"cds-react-aria8760104591-:rgu:-title\">Opens in a new tab</title></svg>](http://man7.org/linux/man-pages/man1/patch.1.html)"
+   ]
   }
  ],
  "metadata": {