Hex Rays decompiler assigns weird looking data types to variables, e.g.
__int64. How do I get to know what all are the built-in data types available in IDA?
The C types in IDA Pro seem to ressemble the Visual C++ syntax.
Read an article written by Hex-Rays https://www.hex-rays.com/products/ida/support/idadoc/1361.shtml
The primitive types that you must know: bool, char, __int8, __int16, __int16, __int32, int, __int64, __int128
you add a keyword 'unsigned' before in the beginning to make the value unsigned.