c-- involve the overall structure of the declarations and
definitions that comprise a program. First, c-- does not
support separate compilation.
Second, c--'s scope rules for external variables allow
forward references. In other words, the scope of an external
declaration is the entire program, not just those parts of the source
code that appear after the declaration. Finally, since the C- compiler
was written slightly before the dawn of time (i.e. 1987), it requires
the use of a syntax for function headers that was revised with the
adoption of ANSI C.
The first two unusual features of c-- make the distinction between
declarations and definitions in C unnecessary. There is no
need to declare functions before they are defined since forward
references are allowed. Thus, while in C it is common to place
a function declaration such as:
double pop();at the beginning of a source file so that the function described can be referenced before it is defined,
c-- does not support
such function declarations. In a c-- source file every
function header must be immediately followed by the appropriate
function body. Similarly, multiple declarations of external
variables are not allowed.
The old style of function declarations that c-- uses requires that the types of function parameters be included in separate, variable-like declarations after a function's header line rather than with the parameter names in the header. Thus, a function that would be declared as
int searchforchar( char *source, char key, int occurrence)
{
...
}
int searchforchar( source, key, occurrence)
char *source;
char key;
int occurrence;
{
...
}
There are several other less significant differences between C declarations
and the declarations that c-- will accept. None of the
"storage class specifiers" that may be included in C declarations
are supported by c--. These include auto, static,
extern, register and typedef. Another limitation
is that c-- does not support initializers in declarations.
Finally, while c-- does support all the structured types
of C including arrays, structures and unions, bit-field components
are not allowed within structures.
The set of scalar types supported by c-- is simpler than
that normally included in C. Only two scalar types are recognized:
int and char. Values of both types are stored in 16 bit words
(the only unit of storage provided by the WC34000).
c-- supports all of the usual types of expressions found
in C, including all of the usual unary and binary operators, subscripting,
component selection, pointer dereferencing, type castes and the
sizeof pseudo-function. With the exception of the switch
statement and the goto statement, all of the usual C statement
types are also recognized.