mov dl, Character ;character to convert
mov ax, 6520h ;Convert Character
int 21h
jc error_handler ;carry set means error
Convert Character (Function 6520h) converts the specified character to an uppercase character using the current uppercase table.
Character
Specifies the character to convert.
The function copies the corresponding uppercase character (if any) to the DL register.
Function 6521h Convert String
Function 6522h Convert ASCIIZ String