diff --git a/2004/sds/README_sds.md b/2004/sds/README_sds.txt
similarity index 100%
rename from 2004/sds/README_sds.md
rename to 2004/sds/README_sds.txt
diff --git a/2004/sds/try.sh b/2004/sds/try.sh
index 7c08f2383..059bff36d 100755
--- a/2004/sds/try.sh
+++ b/2004/sds/try.sh
@@ -30,10 +30,10 @@ echo 1>&2
 make encoder 2>/dev/null
 echo 1>&2
 
-echo "$ ./encoder README_sds.md <sds.c | tee sds_msg.c" 1>&2
+echo "$ ./encoder README_sds.txt <sds.c | tee sds_msg.c" 1>&2
 read -r -n 1 -p "Press any key to continue (space = next page, q = quit): "
 echo 1>&2
-./encoder README_sds.md <sds.c | tee sds_msg.c | less -rEXFK
+./encoder README_sds.txt <sds.c | tee sds_msg.c | less -rEXFK
 
 read -r -n 1 -p "Press any key to run: make sds_msg 2>/dev/null: "
 echo 1>&2
@@ -55,15 +55,15 @@ echo 1>&2
 echo 'Hello, World!' > message
 echo 1>&2
 
-echo "$ ./encoder message < README_sds.md | tee remarks.md" 1>&2
+echo "$ ./encoder message < README_sds.txt | tee remarks.md" 1>&2
 read -r -n 1 -p "Press any key to continue (space = next page, q = quit): "
 echo 1>&2
-./encoder message < README_sds.md | tee remarks.md | less -rEXFK
+./encoder message < README_sds.txt | tee remarks.md | less -rEXFK
 echo 1>&2
 
-read -r -n 1 -p "Press any key to run: diff remarks.md README_sds.md (space = next page, q = quit): "
+read -r -n 1 -p "Press any key to run: diff remarks.md README_sds.txt (space = next page, q = quit): "
 echo 1>&2
-diff remarks.md README_sds.md | less -rEXFK
+diff remarks.md README_sds.txt | less -rEXFK
 echo "Did you notice how similar they are?" 1>&2
 echo 1>&2
 
diff --git a/thanks-for-help.html b/thanks-for-help.html
index 00f699d87..2f36dda7b 100644
--- a/thanks-for-help.html
+++ b/thanks-for-help.html
@@ -2186,7 +2186,7 @@ fast in modern systems, especially the scrolling text of
 <h2 id="sds-index.html"><a name="2004_sds"></a><a href="2004/sds/sds.c">2004/sds</a> (<a href="2004/sds/index.html">index.html</a>)</h2>
 <p><a href="#cody">Cody</a> added the <a href="2004/sds/try.sh">try.sh</a> script.</p>
 <p>Also, after the README.md file had copyright changes, it broke the script so
-Cody made a copy of the older README.md file into <code>README_sds.md</code> and added that
+Cody made a copy of the older README.md file into <code>README_sds.txt</code> and added that
 to the repo for the script instead.</p>
 <h2 id="vik2-index.html"><a name="2004_vik2"></a><a href="2004/vik2/vik2.c">2004/vik2</a> (<a href="2004/vik2/index.html">index.html</a>)</h2>
 <p><a href="#cody">Cody</a> fixed this to compile in Linux. Although it compiled cleanly in macOS (and
diff --git a/thanks-for-help.md b/thanks-for-help.md
index acc983046..2a8457eaf 100644
--- a/thanks-for-help.md
+++ b/thanks-for-help.md
@@ -3167,7 +3167,7 @@ Cody also added the [try.sh](2004/schnitzi/try.sh) script.
 [Cody](#cody) added the [try.sh](2004/sds/try.sh) script.
 
 Also, after the README.md file had copyright changes, it broke the script so
-Cody made a copy of the older README.md file into `README_sds.md` and added that
+Cody made a copy of the older README.md file into `README_sds.txt` and added that
 to the repo for the script instead.