Table 1: Commonly used machine modes in GCC

QImode	Quarter integer mode. Represents a single byte treated as an integer.
HImode	Half integer mode. Represents a two-byte integer.
SImode	Single integer mode. Represents a four-byte integer.
SFmode	Single floating-point mode. Represents a four-byte floating number.
DFmode	Double floating-point mode. Represents an eight-byte floating number.