8086 SUB Instruction 
Edit
Murugan Andezuthu Dharmaratnam | 
13 February 2021 | 
4063
13 February 2021 | 4063
Sub is an arithmetic instruction that subtracts the second operand with the first and stores the result in the first operand.
the second operand can be an immediate number, a register, or a memory location. & the first operand also can be a general-purpose register or a memory location. both operands can be a byte or a word and should be of the same size. If you need to add an 8 bit value ( byte ) to a word you must copy the byte to word location and fill the upper byte of the word with zero before addition.
following flags are affected by an add instruction
AF, CF, OF, SF, ZF
Types of operands supported
Instruction Operands ---------------------------- SUB REG, memory memory, REG REG, REG memory,immediate REG,immediate
Example
mov al,10 ; copy the value 10 to al sub al,02 ; the value of al will be 8 after addition