The usage of GO TO statement

jctgf · Active User Joined: 04 Nov 2006 Posts: 109

i have been reading some opinions about the usage of "go to" on many foruns and i think it's simply ridiculous.

there are cases in which the "go to" statement causes the opposite effect from what is usually expected: it makes the program more clear.

suppose u have a validation program. it reads a sequential file, validate every field and, in case any of the fields contains an error, it discards the record.

Code:

PERFORM READ-FILE.
PERFORM VALIDATION UNTIL READ-RECORD = HIGH-VALUE.

VALIDATION SECTION.
IF A-FIELD NOT NUMERIC
PERFORM WRITE-DISCARD-REC
GO TO READING
END-IF.
IF B-FIELD NOT NUMERIC
PERFORM WRITE-DISCARD-REC
GO TO READING
END-IF.
IF C-FIELD NOT NUMERIC
PERFORM WRITE-DISCARD-REC
GO TO READING
END-IF.
READING.
PERFORM READ-FILE.
VALIDATION-EXIT. EXIT.

is it a bad code? i don't think so...

JC

swapnadeep.ganguly · Active User Joined: 21 Mar 2007 Posts: 203 Location: India

Various clients don't like the usage of GOTO satements. Instead of using a GOTO, you set an error flag.

For subsequent checks, just also check whether the negative error flag is true.

If the negative error flag (ie no error is found on the previous validation) is found, then only the control would check the next conditions.

Some times the GOTO statement acts erroneously due to the usage of GOTO.

pingte · Active User Joined: 03 Dec 2005 Posts: 120 Location: india

u can use Perform instead of GO TO...
using GO TO in not good practice in terms of structured programming!

mahic · New User Joined: 08 Jan 2007 Posts: 4 Location: Mumbai

Hi,
Actually using of GO TO verb soo many times, If use PERFORM READING para inside the PERFORM WRITE-PARA it will be better....becoz if u use GO TO the control will not be coming back from where u have called....

so use PERFORM...instead GO TO

If i am wrong plz correct me......

Mahi

swapnadeep.ganguly · Active User Joined: 21 Mar 2007 Posts: 203 Location: India

Hi,

You can instead use the following codes instead of using GOTO:

dick scherrer · Posted: Mon Jun 04, 2007 7:59 pm

Hello,

The GO TO is neither good nor bad by itself - usage is everything. Some of the very worst code i have ever seen was "structured" and "GOTOless". You don't need the GO TO to write simply horrible code. Some of the very best code i've seen (worked all the time, was easy to maintain, and performed well) included some GO TO statements.

If you have strong feelings on using or not using GO TO, i'd suggest making sure that a company or project has the same feeling you do - preferable before joining.

Because i'm mostly an outsider providing support, i support whatever the rules are at that location.

William Thompson · Posted: Mon Jun 04, 2007 9:02 pm

Well said Dick, I've been biting my lip to avoid saying something un-nice to these young professionals....

TG Murphy · Posted: Mon Jun 04, 2007 11:53 pm

Well here's another view.

In the old days programmers used GO TO in all sorts of inappropriate ways. I recall having to maintain unstructured logic that was full of GO TO's. Nightmare. When structured programming concepts took over, it was necessary to establish strict rules preventing the use of GO TO in order to break old habits.

However, the old days are long gone and the pendulum has swung back. Today it is safe to recognise that there are valid uses for GO TO. The sample code that jctgf shows us is considered to be OK where I work. The only difference is that our shop has this rule: the GO TO paragraph name must use the suffix -EXIT and contain 1 statement: EXIT.

Note: I never use this EXIT approach myself. However, I see it all the time and it doesn't bother me. I just find it is very easy to avoid using it.

Where do I use GO TO?

I use it in error handling logic where there is NO chance that control will be returning. Under this scenario I find that GO TO is better than PERFORM because it makes clear the fact that control will not be coming back. PERFORM is actually misleading in this case but many programmers continue to use PERFORM because they believe it is bad to use GO TO.

The use of GO TO in error handling actually makes your program look better because it avoids cluttering the logic with switches.

Side Note: I locate all my error reporting logic at the bottom of my source file. The reason I do this is to separate the mundane but plentiful error reporting logic from the main logic. Makes the program easier to read.

dick scherrer · Posted: Tue Jun 05, 2007 12:13 am

Hello,

Agreeing with TG's post, i'd like to add one other bit to the 2 GO TO rules he mentioned (going to the end-of-routine exit and going to the error/abend code). The other situation several places use (and i rather like) is that it is permissable to GO TO the top of a routine as well as the bottom/exit. Sometimes this is more clear (understandable/maintainable) and uses less resources than running inside of performs.

In no case should a GO TO be used to transfer control to "somewhere else" where processing would continue. This would be where the infamous "spaghetti code" lives. . . .

especially when that code issues a GO TO back to somewhere already "in flight".

prasadvrk · Posted: Tue Jun 05, 2007 11:22 am

If you have a strict handle on the GOTO you can always use one, after all it serves its purpose. More often than not people use GOTO without knowing the flow of the control. Forward GOTO will never have any problem as there is no confusion about the flow

jasorn · Active User Joined: 12 Jul 2006 Posts: 191 Location: USA