Int 10h, 08h            Read Character and Attribute at Cursor

Reports the ASCII value and (in text mode) attribute of the
character at the current cursor location of the specified display
page.

Entry AH = 08h
BH = Display page number (text modes only)

Return AH = Attribute of character (text mode)
AL = ASCII value of character

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In graphics mode, the display page need not be specified, and the
service returns 00h in AL if it does not recognize the character
pattern (space or tab).