diff --git a/src/base64.gmo b/src/base64.gmo
new file mode 100644
index 0000000..f30b961
--- /dev/null
+++ b/src/base64.gmo
@@ -0,0 +1,5 @@
+# base64
+
+numeral system in base 64: it uses 64 digits, from A to Z, a to z, 0 to 9, and +/ (or -_ for urls)
+
+24 bits correspond to 3 bytes, 4 base64 digits, 6 {hexadecimal} digits, and 8 {octal} digits.
diff --git a/src/hexadecimal.gmo b/src/hexadecimal.gmo
index e7a1c01..4bd92d6 100644
--- a/src/hexadecimal.gmo
+++ b/src/hexadecimal.gmo
@@ -40,3 +40,5 @@ there's a direct mapping between each possible combination of 4 bits (nibble), a
 & * 1101 is d
 & * 1110 is e
 & * 1111 is f
+
+24 bits correspond to 3 bytes, 4 {base64} digits, 6 hexadecimal digits, and 8 {octal} digits.
diff --git a/src/octal.gmo b/src/octal.gmo
new file mode 100644
index 0000000..94fdd2f
--- /dev/null
+++ b/src/octal.gmo
@@ -0,0 +1,31 @@
+# octal
+
+numeral system in base 8: it uses 8 digits, from 0 to 7.
+
+they can be encoded as the eight laban efforts? see {choreutics}
+
+two octal digits correspond to one base64 digit.
+
+24 bits correspond to 3 bytes, 4 {base64} digits, 6 {hexadecimal} digits, and 8 octal digits.
+
++ <table>
++ <tr><th>binary</th><th>hex</th><th>dec</th></tr>
++ <tr><td>000</td><td>0</td><td>0</td></tr>
++ <tr><td>001</td><td>1</td><td>1</td></tr>
++ <tr><td>010</td><td>2</td><td>2</td></tr>
++ <tr><td>011</td><td>3</td><td>3</td></tr>
++ <tr><td>100</td><td>4</td><td>4</td></tr>
++ <tr><td>101</td><td>5</td><td>5</td></tr>
++ <tr><td>110</td><td>6</td><td>6</td></tr>
++ <tr><td>111</td><td>7</td><td>7</td></tr>
++ </table>
+
+& * 000 is 0
+& * 001 is 1
+& * 010 is 2
+& * 011 is 3
+& * 100 is 4
+& * 101 is 5
+& * 110 is 6
+& * 111 is 7
+