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From: mark@cbosgd.UUCP (Mark Horton)
Newsgroups: net.lang
Subject: Re: Language Comparison, Stacks, etc
Message-ID: <435@cbosgd.UUCP>
Date: Fri, 14-Oct-83 14:59:23 EDT
Article-I.D.: cbosgd.435
Posted: Fri Oct 14 14:59:23 1983
Date-Received: Sun, 16-Oct-83 10:59:21 EDT
References: <103@houxk.UUCP>
Organization: AT&T Bell Laboratories, Columbus
Lines: 23

C not only has variant records (e.g. unions), but it is possible to
have DYNAMIC sized records, of a sort.  E.g.
	struct string {
		short length;
		char body[1];
	} *p;
	...
	p = malloc(sizeof (struct string) + strlen(str));
	p->length = strlen(str);
	strcpy(p->body, str);
Try doing THAT in Pascal!

A display is not part of the Pascal Language.  It's a technique a
compiler writer can use in a block structured language to implement
block structure.  It's basically an array of frame pointers, one
for each level of static scoping.  There are other implementations,
for example the P compiler uses a "static link" to the stack frame
of the next static level - to reference a variable 3 levels out,
you follow a chain of static pointers of length 3.  There is a special
pointer for global variables, since they are a common case.  In
ordinary Pascal programs that aren't nested very deep, this works
reasonably well, but in a deeply nested program a display can be
much much faster.