The IDA Pro Book, 2nd Edition

Basic Data Transformations

Properly formatted data can be as important in developing an understanding of a program’s behavior as properly formatted code. IDA takes information from a variety of sources and uses many algorithms in order to determine the most appropriate way to format data within a disassembly. A few examples serve to illustrate how data formats are selected.

1. Datatypes and/or sizes can be inferred from the manner in which registers are used. An instruction observed to load a 32-bit register from memory implies that the associated memory location holds a 4-byte datatype (though we may not be able to distinguish between a 4-byte integer and a 4-byte pointer).

2. Function prototypes can be used to assign datatypes to function parameters. ...