Is there justifying strings to left and right statements in Turbo Pascal?

Question

I searched in Turbo Pascal 6 the complete reference for "rset" and "lset" - statements of QB 4.5 for justifying strings inside their variables bytes - equivalents in Turbo Pascal and found no result as if Turbo Pascal doesn't need these statements or Turbo Pascal is always justifying strings to left. Is this true?

`Turbo Pascal is always justifying strings to left` - in what context, when writing out to console or text file? — 500 - Internal Server Error, Jan 04 '21 at 16:45
I'm searching for justifying in string variables bytes and files — Ahmed Crow, Jan 04 '21 at 16:48
Left-padding a string with spaces to a certain width can be done with something like `function LeftPad(const s: string; len: Integer): string; begin Result := s; while length(Result) < len do Result := ' ' + Result; end;` (line-breaks not included). — 500 - Internal Server Error, Jan 04 '21 at 16:53
But, we can't do it actually in bytes with moving the string to the last bytes of the variable or file buffer, we need to use spaces. — Ahmed Crow, Jan 04 '21 at 18:04
I'm afraid I do not understand your comment. Can you rephrase? — 500 - Internal Server Error, Jan 04 '21 at 20:44
I mean in QB 4.5 "rset" statement for example is justifying the string value to the most right bytes in the variable, I think it doesn't put spaces in left bytes, but maybe null character or something like that. — Ahmed Crow, Jan 05 '21 at 17:07

score 2 · Accepted Answer · answered Jan 05 '21 at 12:22

In Turbo Pascal 6.0 the string type reserves 256 bytes of memory.

s: string;

The memory layout is that the first byte (value 0..255) indicates the length of the string. The following bytes hold the characters, always left aligned.

A variation of the previous is that you can declare string variables with a maximum length, like f.ex.

s: string[10];

This example will reserve 11 bytes of memory. Again the first byte indicates length of the actual string (value in this case 0..10).

The memory content after a statement like

s := 'test';

will be

4, 't', 'e', 's', 't', #0, #0, #0, #0, #0, #0

There is no statement to modify the character allocation to right align the character data (like RSET in QBasic).

However, in theory, you may precede a string with a series of null characters, e.g s :=#0#0#0#0#0#0+'test';, to achieve a similar effect, but the length will become the length of the string variable.

10, #0, #0, #0, #0, #0, #0, 't', 'e', 's', 't'

The null chars are in this case part of the string, and this might be problematic. A null char might be taken for the end of the string. Also, as the null chars might be omitted by e.g. a printing procedure in some case and not in other cases. This could lead to misalignment of data in printouts, or other.

Is there justifying strings to left and right statements in Turbo Pascal?

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