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What are terminal values

what are terminal values

What are the ascii values of up down left right?

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There is no real ascii codes for these keys as such, you will need to check out the scan codes for these keys, known as Make and Break key codes as per helppc 's information. The reason the codes sounds 'ascii' is because the key codes are handled by the old BIOS interrupt 0x16 and keyboard interrupt 0x9.

Hence by looking at the codes following E0 for the Make key code, such as 0x50, 0x4B, 0x4D, 0x48 respectively, that is where the confusion arise from looking at key-codes and treating them as 'ascii'. the answer is don't as the platform varies, the OS varies, under Windows it would have virtual key code corresponding to those keys, not necessarily the same as the BIOS codes, VK_UP, VK_DOWN, VK_LEFT, VK_RIGHT. this will be found in your C++'s header file windows.h, as I recall in the SDK's include folder.

Do not rely on the key-codes to have the same 'identical ascii' codes shown here as the Operating system will reprogram the entire BIOS code in whatever the OS sees fit, naturally that

would be expected because since the BIOS code is 16bit, and the OS (nowadays are 32bit protected mode), of course those codes from the BIOS will no longer be valid.

Hence the original keyboard interrupt 0x9 and BIOS interrupt 0x16 would be wiped from the memory after the BIOS loads it and when the protected mode OS starts loading, it would overwrite that area of memory and replace it with their own 32 bit protected mode handlers to deal with those keyboard scan codes.

Here is a code sample from the old days of DOS programming, using Borland C v3:

This routine actually, returned the codes for up, down is 328 and 336 respectively, (I do not have the code for left and right actually, this is in my old cook book!) The actual scancode is found in the lo variable. Keys other than the A-Z,0-9, had a scan code of 0 via the bioskey routine. the reason 256 is added, because variable lo has code of 0 and the hi variable would have the scan code and adds 256 on to it in order not to confuse with the 'ascii' codes.

Category: Forex

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