Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!decvax!ima!cfisun!lakart!dg
From: dg@lakart.UUCP (David Goodenough)
Newsgroups: comp.misc
Subject: Re: Structured Programming (shading into Computer Folklore)
Message-ID: <447@lakart.UUCP>
Date: 28 Feb 89 15:17:49 GMT
References: <16129@mimsy.UUCP>
Organization: Lakart Corporation, Newton, MA
Lines: 67

From article <16129@mimsy.UUCP>, by chris@mimsy.UUCP (Chris Torek):
> In article <1348@ubu.warwick.UUCP> mirk@warwick.UUCP (Mike Taylor) writes:
>>Hmmm ...  A few years ago BASIC was all I had, structured programming
>>was a closed book to me, and yet I seemed to get by without any of the
>>sorts of problems that Structured Programming is supposed to alleviate.
>>I will admit I never wrote a 10000-line BASIC program, but I certainly
>>got into the 1000s ....  But looking at it objectively, I never had as
>>much difficulty debugging my huge, sprawling unstructured BASIC programs
>>as I do now debugging my huge, sprawling, but structured, C programs.
>>(Only 1/2 a :-)
> 
> Despite the near-necessities missing from most BASICs---local
> variables, for instance---it is possible to write large programs in
> them.  I once (in 1979 or 1980, I suppose) wrote a Z80 assembler in
> TRS-80 Model I Level II BASIC.  The line count was certainly greater
> than 1000.  The system I used was to keep a large sheet of paper
> covered with entry points and variable use.  In fact, I still have that
> paper (curious what one finds in the desk drawers under the H19):
> 	...
> 	10200 - Line input & parsing
> 	...
> 	11200 - O1$: "BC" RP <- 0, "DE" RP <- 1, "HL" RP <- 2,
> 		"AF" RP <- 3, "IX" 4, "IY" 5, else -1
> 	...
> 	12100 - Label table search, FI = `subscr' for label (*not* mod 25)
> 	...
> 	12400 - write 1 disk record, C bytes
> 	...
> (many of these comments now seem unutterably cryptic; but some of it
> comes back to me now).

In a book that has basic programs for the TRS80, the author makes the
following comment (not verbatim, but the meaning is the same)

"You do not need a structured programming language (like PASCAL) to write
structured programs. You need discipline: write all your subroutines, give
them entry and exit points and conditions and variable, comment your loops,
and if's ....."

Is there any _REAL_ difference between:

	while (a < 25)
	 {

	    .....

	 }

AND:

100	REM start "while A < 25" loop
110	if A >= 25 then goto 200
120	.....


190	goto 110
200	REM exit "while A < 25" loop

Local variables are perhaps the hardest problem to solve, but careful variable
name chosing goes a long way. Recursion, I will admit, is a problem. But it
_CAN_ be done, you just need to do a lot of legwork in software, and your
stack space is only as big as you make it.
-- 
	dg@lakart.UUCP - David Goodenough		+---+
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