# Ride Components
Parser checks the Ride script syntax, the presence of all the variables and functions used, and forms an abstract syntax tree that is used by Compiler.
Compiler generates executable script code based on an abstract syntax tree. The compiled script can be assigned to an account or asset.
Estimator calculates the complexity of the compiled script.
Currently the two versions of Estimator are supported:
- version 2 is used after activation of feature #14 “Block Reward and Community Driven Monetary Policy”;
- version 3 is used after activation of feature #15 “Ride V4, VRF, Protobuf, Failed transactions”.
Parser, Compiler and Estimator are used in developer tools such as Waves IDE and Surfboard.
Evaluator is a node component that executes the script in cases of sending a transaction from smart account, invoke script transaction, or transaction involving smart asset. Script execution is a part of transaction validation and transaction execution, that is, calculating new state of the blockchain as a result of transaction.
Decompiler converts script code from executable format to Ride code.
Decompiler is used in Waves Explorer to view an account script, dApp script or asset script.
The decompiled code may not match the source code and may even have incorrect syntax. In particular, it lacks argument types in function declarations.