diff --git a/README.md b/README.md
new file mode 100644
index 0000000..aa1ae84
--- /dev/null
+++ b/README.md
@@ -0,0 +1,56 @@
+# abcs
+A libabacus front end for the command-line.
+
+## Syntax
+Please see the libabacus documentation (external/libabacus/README.md) for a guide through the syntax.
+
+## Implementation
+abcs uses GNU MPFR for its number implementations. It keeps 200 digits of precision, and displays up to 50. By default,
+3 digits are displayed. The `request_precision` function can be used to request more digits to be displayed.
+
+## RC File
+abcs loads, by default, an `.abcsrc` file in the same directory in which it is run. It parses the whole file ingoring
+newlines and spaces, and evaluates it in order. The RC file can be used to specify constants or declare functions that
+the user wants to re-use between sessions.
+
+## Provided Functions and Operators
+|Operator|Function|Precedence|
+|--------|--------|----------|
+| <  | lt | 1 |
+| <= | lte | 1 |
+| == | equals | 1 |
+| >  | gt | 1 |
+| >= | gte | 1 |
+| +  | plus | 2 |
+| -  | minus | 2 |
+| *  | times | 3 |
+| /  | divide | 3 |
+| ^  | pow | 3 |
+| -  | negate | (prefix) |
+| !  | factorial | (postfix) |
+
+|Function|Description|
+|--------|----|
+|lt | less than comparator.|
+|lte | less than or equal comparator.|
+|equals| equality comparator. |
+|gt| greater than comparator. |
+|gte| greater than or equal comparator. |
+|plus| addition function. |
+|minus| subtraction function. |
+|times| multiplication function. |
+|divide| division function. |
+|pow| exponentiation function |
+|negate| flip sign of number. |
+|factorial| factorial via the gamma function. |
+|ln|natural logarithm function.|
+|exp| e to the nth power function.|
+|sqrt| square root function.|
+|sin| trigonometric sine function. |
+|cos| trigonometric cosine function. |
+|tan| trigonometric tangent function. |
+|arcsin| trigonometric inverse sine function. |
+|arccos| trigonometric inverse cosine function. |
+|arctan| trigonometric inverse tangent function. |
+|quit| quits the REPL. |
+|request\_precision| requests the given number of digits to be displayed in the REPL. |
diff --git a/external/libabacus b/external/libabacus
index 0172091..899ac31 160000
--- a/external/libabacus
+++ b/external/libabacus
@@ -1 +1 @@
-Subproject commit 01720914e0899023747c94ef7cf4c5d17782d7dd
+Subproject commit 899ac31210d31bea3b08bc94fc03432dd8a6029e