Const Type Specifier - Texas Instruments TI-89 Software Manual

Section 2: Compiler
2.9.8.

Const Type Specifier

The value of an object that is declared with the const type specifier cannot be
modified; therefore, the object cannot appear as the left-hand side of an
assignment, nor as the operand of the '++' or '
examples demonstrate the legality of various modifications involving const
objects:
The const type specifier can be used with integer types, floating-point types,
structure and union types, and enumeration types. It can also be used with
individual members of structures and unions, in which case only the specified
members are affected. If the const type specifier is used without any other type
specifiers or with only the volatile type specifier (see below), type int is implied.
The const type specifier can also be used to declare pointers to constant objects
and constant pointers to constant and nonconstant objects. Just as an asterisk
( * ) in a declaration indicates a pointer to an object, the construct *const
indicates a constant pointer to an object. A constant pointer cannot be modified;
no restrictions are placed on the object to which it points. The following
declarations define a constant int, a constant pointer to an int, and a constant
pointer to a pointer to a constant pointer to a constant double, respectively:
A pointer to a nonconstant object can be assigned to a pointer to either a
constant or nonconstant object; however, a pointer to a constant object can only
be assigned to a pointer to a constant object. These pointer assignment rules
were established to help prevent accidental modifications of constant objects with
dereferenced pointers to nonconstant objects. These rules can be easily
sidestepped with a type cast, but this is not recommended since it could result in
an attempt to modify data stored in Read-Only Memory (ROM).
TI-89 / TI-92 Plus Sierra C Assembler Reference Manual
const int a = 99;
const int b = 66;
const int *p = &a;
a++;
b ;
a = 10;
p = &b;
*p = 20;
const int a;
int * const b;
const double * const ** const c;
' operator. The following
/* illegal */
/* illegal */
/* illegal */
/* legal */
/* illegal */
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Beta Version February 2, 2001