INFO: Return Value for getch() on Extended Characters

ID: Q57888

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

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:

Keywords : kbcode kbCRT kbVC100 kbVC150 kbVC200 kbVC210 kbVC400 kbVC500 kbVC600
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