Frame: what changed

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Title: Frame

New		Line
1	+	A frame (frequently also referred to as [[Block\|block]]) is a language construct grouping a (possibly empty) sequence of [[statement\|statements]] (or instructions in the case of `asm` frames).
2	+
3	+	## available types
4	+
5	+	All frames but [[Repeat\|repeat … until]] are terminated by the word [[End\|end]]. Frame types are distinguished by their corresponding opening words.
6	+
7	+	- [[Pascal]]: These frames expect Pascal statements or may contain other frames.
8	+	[[Begin\|begin]]
9	+	This frame begins a (possibly empty) sequence of statements. In the context of [[Routine\|routine]] definitions or a [[Program\|program]] it can delimit a [[Scope\|scope]].
10	+
11	+	[[Else\|else]]/`otherwise`
12	+	This frame surrounds a “catch-all”-alternative as part of a [[Case\|case statement]].
13	+
14	+	`repeat … until`
15	+	`repeat` in conjunction with `until` is used to surround the loop body of a tail-controlled [[Loops\|loop]]. It is the only frame type not ending with an `end`.
16	+
17	+	exception treatment
18	+	If [[Exceptions\|exceptions]] are supported in the current compiler mode, the following frames are available as well. These frames are in fact “double”-frames: They group two sequences at once. Neither of them can be used independently (e. g. writing `finally … end;` without a proper `try` is illegal).
19	+
20	+	[[Try\|try]] … [[Except\|except]] …
21	+	Use this to install exception handlers.
22	+
23	+	`try` … [[Finally\|finally]] …
24	+	Use this to ensure a certain code fragment is executed despite any thrown exceptions.
25	+
26	+	[[Unit\|unit]] overhead
27	+
28	+	:; [[Initialization\|initialization]] … [[Finalization\|finalization]]
29	+
30	+
31	+
32	+	This double-frame designates code being executed when the corresponding unit is loaded or unloaded. Either part of this frame is optional. This frame may also delimit a scope.
33	+	- [[Assembly language]]: Frames beginning with [[Asm\|asm]] expect assembly language. In pure assembly routines, this kind of frame may delimit a scope, too. Note, you cannot nest other frames in `asm` frames.
34	+
35	+	## style
36	+
37	+	Although not mandatory, it is customary to indent all code surrounded by frame markers by one level.
38	+
39	+	```delphi
40	+	try
41	+	openJar;
42	+	except
43	+	throwATantrum;
44	+	end;
45	+	```
46	+
47	+	Some styles add another indentation level for nested or subordinate frame markers per se.
48	+
49	+	``` pascal
50	+	if apples = oranges then
51	+	begin
52	+	protest;
53	+	halt(123);
54	+	end;
55	+	```
56	+
57	+	As you can see from the examples above, it is customary to put frame delimiters isolated in their own line. Exempt of this guideline are of course frames accepting or requiring additional clauses to be syntactically complete:
58	+
59	+	``` pascal
60	+	repeat
61	+	write('Enter a non-negative integer: ');
62	+	readLn(i);
63	+	until i >= 0;
64	+	```
65	+
66	+	```delphi
67	+	asm
68	+	rdrand eax
69	+	mov n, eax
70	+	end ['eax'];
71	+	```
72	+
73	+	## technical background
74	+
75	+	Frames frequently, but not always, turn up to be (conditional) `jmp` targets. Some compile-time optimizations require code to be structured in a certain way, frames setting boundaries for that.
76	+
77	+	---
78	+	From the Free Pascal wiki, page "Frame", as it stood on 2021-02-06 after a change by Kai Burghardt, out of the wiki's dump of 2024-05-26. Copyright stays with the author who wrote it, according to the old wiki's [[Licensing]] page. If you have concerns about this material, [message the admin](/wiki-contact).
79	+	Category: Glossary
80	+	Category: Pascal

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