diff --git a/doc/syscalls.md b/doc/syscalls.md
index 4088f22..57636fe 100644
--- a/doc/syscalls.md
+++ b/doc/syscalls.md
@@ -181,7 +181,7 @@ Arguments:
     Y: Address of buffer
 
 Return Values: 
-    C: Status code
+    C: Status code
 
 Argument Structure:
 
@@ -222,17 +222,17 @@ Arguments:
 
 Return Values: 
     C: Status code
-    X: File handle
+    X: File handle
 
 This call attempts to open the file referred to by the provided NULL-terminated
 string, which must contain a fully-qualified pathname -- something of the form
 `[drive]:/[dir]/[dir2]/filename.ext`, such as `sd0:/games/kaboom/readme.ansi`.
 
 If the file is successfully opened, the C accumulator will contain STATUS_OK, and
-the X register will contain the file handle. On error, the C accumulator will contain 
+the X register will contain the file handle. On error, the C accumulator will contain 
 a negative value indicating which error has occured.
 
-## 0x0E: Close File
+## 0x0E: Close File Handle
 
 Arguments:
     C: 0x0E
@@ -261,16 +261,16 @@ On success, the C accumulator will contain a status code of STATUS_OK, and the X
 register will contain the duplicate file handle. On error, the C accumulator will 
 contain a negative value, indicating an error has occured.
 
-## 0x10: Read from File Handle
+## 0x10: Read from File
 
 Arguments:
     C: 0x10
     X: Bank of argument block
-    Y: Address of argument block
+    Y: Address of argument block
 
 Return Values:
-    C: Status code
-    X: Number of bytes actually read
+    C: Status code
+    X: Number of bytes actually read
 
 Argument block structure:
 
@@ -283,20 +283,20 @@ Argument block structure:
 
 This call attempts to read up to `length` bytes from the file handle `file`, into
 the buffer pointed to by `dest`. On success, the C accumulator will contain STATUS_OK,
-and the X register will contain the number of bytes actually read. On error, the C
+and the X register will contain the number of bytes actually read. On error, the C
 accumulator will contain a negative value indicating the specific error, and the X
 register will contain the number of bytes actually read.
 
-## 0x11: Write to File Handle
+## 0x11: Write to File
 
 Arguments:
     C: 0x11
     X: Bank of argument block
-    Y: Address of argument block
+    Y: Address of argument block
 
 Return Values:
-    C: Status code
-    X: Number of bytes actually written
+    C: Status code
+    X: Number of bytes actually written
 
 Argument block structure:
 
@@ -309,6 +309,26 @@ Argument block structure:
 
 This call attempts to write up to `length` bytes to the file handle `file`, from
 the buffer pointed to by `src`. On success, the C accumulator will contain STATUS_OK,
-and the X register will contain the number of bytes actually written. On error, the C
+and the X register will contain the number of bytes actually written. On error, the C
 accumulator will contain a negative value indicating the specific error, and the X
-register will contain the number of bytes actually written.
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+register will contain the number of bytes actually written.
+
+## 0x12: Seek in File
+
+Arguments:
+    C: 0x12
+    X: Seek value
+    Y: Seek origin
+        0x00: Seek relative to the beginning of the file
+        0x01: Seek relative to the current position in the file
+        0x02: Seek relative to the end of the file
+
+Return value:
+    C: Status code
+    X: New file position (31:16)
+    Y: New file position (15:0)
+
+This call moves the internal file pointer, the position in the specified file from
+which data can be read or to which data can be written. On success, this call returns
+STATUS_OK in C, and the new file position in X and Y. On error, C will contain a negative
+value indicating the specific error, and the new file position in X and Y.
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