INT 21H (0x21) function 08H (0x08) Character input without echo 09H (0x09) Display string 0AH (0x0A or 10) Buffered keyboard input 0BH (0x0B or 11) Check input status 0CH (0x0C or 12) Flush input buffer and then Input

INT 21H (0x21)

Function 08H (0x08) --> Character input without echo

Call with: AH = 08H

Returns: AL = 8-bit input data

Comments:

This function reads a character from the standard input device without echoing it to the standard output device.

INT 21H (0x21)

Function 09H (0x09) --> Display string

Call with: AH = 09H
DS:DX = segment: offset of string

Returns: Nothing

Comments:

It sends a string of characters to the standard output device. Output may be redirected. If output has been redirected, there is no way to detect disk full. String can also be sent to the display by performing a write (INT 21H Function 40H) using the predefined handle for the standard output (0001H), if it has not been redirected, or a handle obtained by opening the logical device CON.

INT 21H (0x21)

Function 0AH (0x0A or 10) --> Buffered keyboard input

Call with: AH = 0AH
DS:DX = segment: offset of buffer

Returns: Data placed in buffer, Returns Nothing

Comments:

It reads a string of bytes from the standard input device, up to and including an ASCII carriage return (0DH), and places them in a user-designated buffer. The characters are echoed to the standard output device. The buffer used by the function has following format:

INT 21H (0x21)

Function 0BH (0x0B or 11) --> Check input status

Call with: AH = 0BH

Returns: AL = 00H (if no character is available)
FFH (if at least one character is available)

Comments:

Checks if a character is available from the standard input device such as keyboard. This function is equivalent to IOCTL INT 21H Function 44H Sub function 06H.

INT 21H (0x21)

Function 0CH (0x0C or 12) --> Flush input buffer and then Input

Call with: AH = 0CH
AL = number of input to be invoked after resetting
buffer (must be 01H, 06H, 07H, 08H or
0AH)

If AL = 0AH
DS: DX = segment: offset of input buffer

Returns: If called with AL = 01H, 06H, 07H, or 08H,
AL = 8-bit input data

If called with AL= 0AH,
Nothing (data placed in buffer)

Comments:

Clears the standard input buffer and then invokes one of the character input functions. Input can be redirected. A function number in AL except 01H, 06H, 07H, 08H, or 0AH flushes the input buffer and returns control to the calling program.

Sample Chapters from book DATA RECOVERY WITH AND WITHOUT PROGRAMMING by Author Tarun Tyagi

Publishers of the Book Number of Pages ISBN Price of the Book BPB Publications, New Delhi, India 540 81-7656-922-4 $69.00 (Including Shipping Charges, Cost of Book and Other expenses, Free Source Code CD included with the Book)

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