String Conversion — DTOS, STOD, RTOS, STOR, UPPER, LOWER

A display shows text, and a barcode reader or a serial device sends text. Your logic works with numbers. These instructions cross between the two, and change the case of letters so two pieces of text can be compared whatever case they were typed in.

Each one is a statement of its own that writes its result into its last operand. None of them gives back a value, so Speed := STOD(Reply); is refused: write STOD(Reply, Speed);.

DTOS(PartCount, CountText);    (* -42 gives '-42' *)
STOD(Reply, Speed);            (* '1500 rpm' gives 1500 *)
RTOS(Temperature, TempText);   (* 21.5 gives '21.5000000' *)
STOR(Reply, Pressure);         (* 'P=2.75bar' gives 2.75 *)
UPPER(Typed, Code);            (* 'ab-12x' gives 'AB-12X' *)
LOWER(Typed, Code);            (* 'AB-12X' gives 'ab-12x' *)

OperandsCopy Anchor Link

A source is a tag, or for DTOS and RTOS a number typed in, never an expression: DTOS(Count + 1, CountText); is refused, so work Count + 1 out into a tag first. Text in quotes goes only in := and in a comparison, never into these.

What each one writesCopy Anchor Link

• DTOS makes a REAL a whole number first, the way := stores a REAL into a DINT: a half goes to the even neighbour, so 2.5 gives '2' and 3.5 gives '4'. It clears the whole destination before it writes.
• STOD skips everything up to the first digit, then reads digits until something that is not one. A - counts only directly before the first digit, so 'SPD=-20' gives -20 and '12.7' gives 12. No digit at all gives 0. A number too large for a DINT is held to the DINT limit, with a warning; into an INT or a SINT it then wraps as any store does.
• RTOS always writes nine digits: eight decimals from 0.0001 up to 1, nine digits in all from 1 up to 10000000, and nine digits with an exponent otherwise, as in '1.23456780e+07'. Zero gives '0.0'. The digits are the REAL's own, so 123.456 gives '123.456001'.
• STOR reads like STOD, then a decimal point and more digits, and an exponent such as e3. Text starting 0x reads as hexadecimal: '0x1F' gives 31.0. A number a REAL cannot hold gives Infinity, with a warning.
• UPPER and LOWER change only the letters a to z and A to Z.

When the source's LEN is outside 0 to 82, none of them reads it: UPPER and LOWER leave the destination as it was, STOD and STOR store 0, and Studio shows a warning.

Common MistakesCopy Anchor Link

• Expecting STOR to read '.5' as 0.5. It starts at the first digit, so it reads 5.
• Expecting STOD to round. '12.7' gives 12. Use STOR and then := into a DINT.

RelatedCopy Anchor Link

• String instructions — join, find and cut text
• String conversion in Ladder