# Codes of Errors and Warnings

This section contains the following descriptions:

- [Return codes of the trade server](/en/docs/constants/errorswarnings/enum_trade_return_codes) – analyzing results of the [trade request](/en/docs/constants/structures/mqltraderequest) sent by function [OrderSend()](/en/docs/trading/ordersend);
- [Compiler warnings](/en/docs/constants/errorswarnings/warningscompile) – codes of warning messages that appear at compilation (not errors);
- [Compilation errors](/en/docs/constants/errorswarnings/errorscompile) – codes of error messages at an unsuccessful attempt to compile;
- [Runtime errors](/en/docs/constants/errorswarnings/errorcodes) – error codes in the execution of mql5-programs, which can be obtained using the [GetLastError()](/en/docs/check/getlasterror) function.