Documentation of kernel API

doc/syscalls.md

@@ -486,4 +486,53 @@ any device alias, or if the `alias` argument value is already in use
 as a device alias.
 
 On success, `C` will contain `STATUS_OK`. On error, `C` will contain
-a negative value which indicates the specific error type.
+a negative value which indicates the specific error type.
+
+## `0x1A`: Get Environment Variable
+
+Arguments:
+ - `C`: `0x1A`
+ - `X`: Bank of argument structure
+ - `Y`: Address of argument structure
+
+Return Values:
+ - `C`: Status code
+
+Argument Structure:
+
+```
+    struct {
+        char *name; // The name of the variable to read
+        char *value; // Buffer for the value of the variable
+    };
+```
+
+This call gets the value of an environment variable specified by the 
+`name` field of the argument structure, and copies it into the buffer
+pointed to by the `value` field. If the variable is not set, the value
+will be set to `NULL`, and the status code will be `ERR_ENV_UNSET`; otherwise
+the status code will be `STATUS_OK`.
+
+## `0x1B`: Set Environment Variable
+
+Arguments:
+ - `C`: `0x1A`
+ - `X`: Bank of argument structure
+ - `Y`: Address of argument structure
+
+Return Values:
+ - `C`: Status code
+
+Argument Structure:
+
+```
+    struct {
+        char *name; // The name of the variable to set
+        char *value; // Buffer for the new value of the variable
+    };
+```
+
+This call sets the value of an environment variable specified by the 
+`name` field of the argument structure by copying the string pointed 
+to by the `value` field. To unset a variable, pass `NULL` in the `value`
+field. This call always returns `STATUS_OK`.