OllyDbg is a 32-bit assembler level analysing debugger for Microsoft Windows.
IDA is the Interactive DisAssembler: the world's smartest and most feature-full disassembler, which many software security specialists are familiar with. Written entirely in C++, IDA runs on the three major operating systems: Microsoft Windows, Mac OS X, and Linux.
IDA is also the solid foundation on which our second product, the Hex-Rays decompiler, is built.
The unique Hex-Rays decompiler delivers on the promise of high level representation of binary executables. It can handle real world code.