5. The input Macro (read ASCII characters)

• Inputs a string of characters from the keyboard.

• It has two parameters, destination and length:

  • input destination, length

  where

  • destination operand references a string of bytes in the data segment

  • length operand references the number of bytes reserved in the destination string.

• For example,

      .DATA           ; Begin initialized data segment
          buffer      BYTE    12 DUP (?)
          ..
      .CODE           ; Code segment
          ..
          input   buffer, 12  ; Read zero to 10 ASCII characters
          ..
  

• Important: The destination string should be at least two bytes longer than the actual number of characters to be entered.

  • This allows for the operating system to add carriage return and line feed characters when user presses the Enter key.

• The input macro automatically replaces the carriage return character by a null byte.

• The result is a null-terminated string stored at the destination.

• The input macro updates memory at the specified destination.

• Flags or registers affected: none.