INFO: Return Value for getch() on Extended Characters

• 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, versions 1.0, 1.5 - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 2.1, 4.0, 5.0

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 */
   }

Keywords          : CRTIss kbcode kbfasttip
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
Platform          : MS-DOS NT WINDOWS
Issue type        : kbinfo