To assign a name to a constant, we can use the EQU (equates) pseudo-op. THe syntax is
name EQU constant
For Example : the statement
LF EQU 0AH
assigns the name LF to 0Ah, the ASCII code of the line feed character. The name LF may now be used in place of 0Ah anywhere in the program. Thus, the assembler translates the instructions
MOV DL, 0AH
into the same machine instruction
The symbol on the right of an EQU can also be a string
PROMPT EQU 'TYPE YOUR NAME'
Then instead of
MSG DB 'TYPE YOUR NAME'
we could say
MSG DB PROMPT
Note : no memory is allocated for EQU names.