These instructions permit the use of the stack to store or recover data.
POP
POPF
PUSH
PUSHF
POP INSTRUCTION
Purpose: It improves a portion of information from the stack
POPF INSTRUCTION
Purpose: It extracts the flags stored on the stack
POPF
This command moves bits of the word stored on the superior part of the stack to the flag register.
PUSH INSTRUCTION
Purpose: It puts a word on the stack.
Syntax:
PUSH source
The PUSH instruction reduces by two the value of SP and then transfers the data of the source operator to the new resulting address on the just modified register.
The decrement on the address is due to the fact that when adding values to the stack, this one raises from the greater to the smaller segment address, consequently by subtracting 2 from the SP register what we do is to raise the size of the stack by two bytes, which is the only amount of information the stack can handle on every input and output of information.
PUSHF INSTRUCTION
Purpose: It situates the value of the flags on the stack.
Syntax:
PUSHF
This command reduces by 2 the value of the SP register and then the content of the flag register is relocated to the stack, on the address indicated by SP.
The flags are gone stored in memory on the similar bits indicated on the POPF command.