Q57888: INFO: Return Value for getch() on Extended Characters

Article: Q57888
Product(s): Microsoft C Compiler
Version(s): MS-DOS:5.1,6.0,6.00a,6.00ax,7.0; WINDOWS:1.0,1.5; WINDOWS NT:1.0,2.0,2.1,4.0,5.0
Operating System(s): 
Keyword(s): kbcode kbCRT kbVC100 kbVC150 kbVC200 kbVC210 kbVC400 kbVC500 kbVC600
Last Modified: 25-JUL-2001

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The information in this article applies to:

- The C Run-Time (CRT), included with:
   - Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, 6.0ax 
   - Microsoft C/C++ for MS-DOS, version 7.0 
   - Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5 
   - Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 4.0, 5.0, 6.0 
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SUMMARY
=======

In Microsoft C, when reading extended characters you must make two calls to
getch() because the first call returns a value indicating that the key is an
extended character. The second call returns the actual key code.

MORE INFORMATION
================

When you are reading an extended character, the first return value will be
either 0xE0 or 0x00, depending on which extended key is pressed.

Sample Code
-----------

  #include <stdio.h>
  #include <conio.h>

  void main(void)
  {
      int ch, scan;

      do {
          ch = getch();    /* 1st getch() gets ASCII code */ 
          printf("Character is %d\n", ch);
             if (ch == 0x00 || ch == 0XE0)  { /* if extended key */ 
              scan = getch();  /* 2nd getch() gets "scan code" */ 
              printf("\tExtended character:  scan is %d\n", scan);
          }
      }  while (ch != 27);    /* exit loop on ESC */ 
  }

For a discussion of keystrokes and scan codes, refer to "The New Peter Norton
Programmer's Guide to the IBM PC & PS/2," by Peter Norton and Richard
Wilton.

Additional query words:

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Keywords          : kbcode kbCRT kbVC100 kbVC150 kbVC200 kbVC210 kbVC400 kbVC500 kbVC600 
Technology        : kbVCsearch kbAudDeveloper kbCRT
Version           : MS-DOS:5.1,6.0,6.00a,6.00ax,7.0; WINDOWS:1.0,1.5; WINDOWS NT:1.0,2.0,2.1,4.0,5.0
Issue type        : kbinfo

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