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Microsoft KB Archive/37163

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Knowledge Base

How to INPUT Text without CTRL+BREAK Stopping Execution

Article ID: 37163

Article Last Modified on 11/21/2006

This article was previously published under Q37163


When an INPUT or LINE INPUT statement is pending to accept text, the program will always stop if you press CTRL+BREAK. CTRL+BREAK aborts the program even when the program is compiled without the /D (debug) option. [Pressing CTRL+BREAK will not stop programs compiled without /D (debug) if no INPUT or LINE INPUT statement is currently pending.]

Also, events such as ON KEY(n) GOSUB key trapping and ON ERROR GOTO error handling are suspended until the INPUT or LINE INPUT statement is satisfied by pressing the ENTER key.

This behavior applies to Microsoft QuickBasic Versions 1.00, 1.01, 1.02, 2.00, 2.01, 3.00, 4.00, 4.00b, and 4.50; to Microsoft Basic Compiler Versions 6.00 and 6.00b for MS-DOS and MS OS/2; and to Microsoft Basic PDS Version 7.00 for MS-DOS and MS OS/2.

You will need to use a method other than INPUT and LINE INPUT to both suppress CTRL+BREAK and allow input, and to allow events to be handled while input is taking place. The easiest method to use is a loop structure that monitors the value of the INKEY$ function and makes the appropriate changes to the input string. Below is an example of how to write your own INPUT statement. For another example of how to write your own INPUT statement, query on the following words:

QuickBasic and buffered and keyboard and input and cursor


The program listing below demonstrates how to use INKEY$ in a loop to simulate the operation of INPUT or LINE INPUT. The program checks the value of INKEY$, and acts on the value accordingly, such as handling backspaces, carriage returns, and non-printable characters. This routine can easily be modified to allow other features, such as filling the edit field to the specified size with a fill character, recognizing function keys to perform various functions, etc.

The following is a code example:

'--- Copyright (c) 1988 Microsoft Corporation
'--- This program demonstrates the subprogram TextInput as a
'--- substitute for Basic's INPUT and LINE INPUT statements.
'--- When compiled without the /D (debug) option, pressing
'--- CTRL+BREAK will not stop this program.
DECLARE SUB TextInput (text$, MaxLen%)
text$ = "This is a sample"
PRINT "Enter some text:";
TextInput text$, 45
PRINT "The line you entered:"
PRINT text$

'--- TextInput
'--- Accepts a line of text from the user
'--- Text$   : Default string/destination string input by user
'--- MaxLen% : Maximum length of destination string, up to 80 chars
SUB TextInput (text$, MaxLen%) STATIC
  '--- Set up cursor, line, and maximum characters to enter:
  y% = CSRLIN
  LOCATE , , 1
  IF MaxLen% > (79 - POS(0)) THEN MaxLen% = (79 - POS(0))
  '--- Display default text:
  PRINT text$;
  '--- Do the input loop:
    i$ = INKEY$
    SELECT CASE LEFT$(i$, 1)
      CASE CHR$(8)                      '--- Handle a backspace
        IF text$ > "" THEN
          text$ = LEFT$(text$, LEN(text$) - 1)
          LOCATE y%, POS(0) - 1
          PRINT " ";
          LOCATE , POS(0) - 1
        END IF
      CASE CHR$(32) TO CHR$(255)        '--- Valid characters
        IF LEN(text$) <= MaxLen% THEN
          PRINT LEFT$(i$, 1);
          text$ = text$ + LEFT$(i$, 1)
        END IF
      CASE "", CHR$(13)                 '--- Null or carriage return
      CASE ELSE                         '--- Non-printables, etc.
  LOOP UNTIL i$ = CHR$(13)
  LOCATE , , 0

Additional query words: QuickBas BasicCom

Keywords: KB37163