ARM Architecture Reference Manual ARMv7-A and ARMv7-R edition

I.3 Data types
This section describes:
General data type rules
Bitstrings
Integers on page AppxI-6
Reals on page AppxI-6
Booleans on page AppxI-6
Enumerations on page AppxI-6
Lists on page AppxI-7
Arrays on page AppxI-8.
I.3.1 General data type rules
Pseudocode Definition
ARM architecture pseudocode is a strongly-typed language. Every constant and variable is of one of the
following types:
bitstring
integer
boolean
real
enumeration
list
array.
The type of a constant is determined by its syntax. The type of a variable is normally determined by
assignment to the variable, with the variable being implicitly declared to be of the same type as whatever is
assigned to it. For example, the assignments x = 1, y = '1', and z = TRUE implicitly declare the variables
x, y and z to have types integer, length-1 bitstring and boolean respectively.
Variables can also have their types declared explicitly by preceding the variable name with the name of the
type. This is most often done in function definitions for the arguments and the result of the function.
These data types are described in more detail in the following sections.
I.3.2 Bitstrings
A bitstring is a finite-length string of 0s and 1s. Each length of bitstring is a different type. The minimum
permitted length of a bitstring is 1.
The type name for bitstrings of length N is bits(N). A synonym of bits(1) is bit.
Bitstring constants are written as a single quotation mark, followed by the string of 0s and 1s, followed by
another single quotation mark. For example, the two constants of type bit are '0' and '1'. Spaces can be
included in bitstrings for clarity.
ARM DDI 0406B Copyright © 1996-1998, 2000, 2004-2008 ARM Limited. All rights reserved. AppxI-5