I wrote a script in ksh93 (the OS is AIX 5.2, ML7), which failed to run. After some testing i found out why, but the answer is a bit dissatisfying. Look for yourself:

#!/bin/ksh93

# --------- Step Names
typeset achStepName[1]="foo"
typeset achStepName[2]="bar"
typeset achStepName[3]="fubar"
typeset achStepName[4]="test"

(( iCnt = 1 ))
while [ $iCnt -le ${#achStepName[@]} ] ; do
     print - $iCnt ${achStepName[$iCnt]}
     (( iCnt += 1 ))
done

exit 0

1
2 bar
4 fubar
4 test

0 foo
1
2 bar
4 fubar
4 test

Wow! The problem all lies here....

typeset achStepName[1]="foo"
typeset achStepName[2]="bar"
typeset achStepName[3]="fubar"
typeset achStepName[4]="test"

Hmm....

Actually i didn't know all that about variable handling in the ksh, so many thanks for explaining this.

On the other hand, in ksh(88) the code works as expected: the four statements generate a table with four elements and indices 1,2,3,4. The expression ${#table[@]} evaluates to 4 and the loop works fine.

I tried this now on another machine (AIX 5.1, ML06) and there it worked to what i would have expected too.

As I have understood my ksh manual "arr[n]" not only sizes an array but also denotes a specific array element. Otherwise the expression "print - "${arr[3]}" wouldn't make sense, right?

Further, the ksh93 man page states, that ksh93 now has "associative arrays" and i don't see the difference between "arr[tommy]", "arr[willy]" and "arr[1]". Since the first two values will not (for obvious reasons) be zero-based, why has the latter one to be?

bakunin

Retry all of those version of ksh using something like "typeset -Z9 zeros[7]=123". You will probably find that the 2 statements:
typeset -Z9 zeros[7]=123
typeset zeros[7]=123
work differently. And remember, "zeros" must be undefined to see the difference. On your ksh93 the two statements will both set zeros[0]=123 on the first execution. And they both will set zeros[7]=123 on the second execution.

What arr[n] does depends on where it is used. There is no language on the ksh93 man page stating that an array reference is allowed at all in a typeset statement. Only is the ksh book is there some fleeting mention of using typeset vname[n] to declare an indexed array.

Why do indexed arrays need to start with zero? Because that is way the language works. Dave Korn could have decreed that they start with 1 or even 719. He picked 0, probably because C does. Without a standard, stuff like:
array=(aaa bbb ccc)
set -A array aaa bbb ccc
would not make sense. ksh93 has blurred the distinction bewteen associative arrays and indexed arrays as much as is possible. I am disaapointed with that particular design choice and it is adding to the confusion here. You seem to have lost the concept entirely. I hope this isn't because your ksh93 is broken. Try this:
x[2]=7
x[1+1]=9
echo ${x[2]}
typeset -A x
x[2]=7
x[1+1]=9
echo ${x[2]}
When I run this, I get 9 the first time and 7 the second.