Address of a variable: Difference between revisions

=={{header|Draco}}==

<lang draco>/* This code uses a CP/M-specific address to demonstrate fixed locations,

* so it will very likely only work under CP/M */

proc nonrec main() void:

/* When declaring a variable, you can let the compiler choose an address */

word var;

/* Or you can set the address manually using @, to a fixed address */

word memtop @ 0x6; /* CP/M stores the top of memory at 0x0006 */

/* or to the address of another variable, by naming that variable */

word var2 @ var; /* var2 will overlap var */

/* This works with both automatically and manually placed variables. */

word memtop2 @ memtop; /* same as "memtop2 @ 0x6" */

/* Once a variable is declared, you can't change its address at runtime. */

var := 1234; /* assign a value to var _and_ var2 */

/* The address of a variable can be retrieved using the & operator.

* However, this returns a pointer type, which is distinct from an

* integer type. To use it as a number, we have to coerce it to an integer

* first. */

writeln("var address=", pretend(&var,word):5, " value=", var:5);

writeln("memtop address=", pretend(&memtop,word):5, " value=", memtop:5);

writeln("var2 address=", pretend(&var2,word):5, " value=", var2:5);

writeln("memtop2 address=", pretend(&memtop2,word):5, " value=", memtop2:5)

corp</lang>

{{out}}

<pre>var address= 276 value= 1234

memtop address= 6 value=58374

var2 address= 276 value= 1234

memtop2 address= 6 value=58374</pre>