mov dx, seg String
mov ds, dx
mov dx, offset String ;ds:dx points to string to convert
mov ax, 6522h ;Convert ASCIIZ String
int 21h
jc error_handler ;carry set means error
Convert ASCIIZ String (Function 6522h) converts each character in the specified string to an uppercase character using the current uppercase table.
String
Points to a zero-terminated string.
The function replaces the original characters in the string with the corresponding uppercase characters (if any).
Function 6520h Convert Character
Function 6521h Convert String