Assembly Language Learning Notes (10) Call and RET directives work together

1.ret and RETF
RET: The instruction uses the data in the stack, modifies the IP content, thus realizes the near transfer
When the CPU executes the RET instruction, the following two steps are taken:
1) (IP) = ((ss) *16+ (SP))
2) (SP) = (sp) +2
Equivalent to a pop IP

RETF: Using the data in the stack, modify CS and IP content, so as to achieve far transfer
1) (IP) = ((ss) *16+ (SP))
2) (SP) = (sp) +2
3) (CS) = ((ss) *16+ (SP))
4) (SP) = (sp) +2
Equivalent to pop IP pop CS

Call Label: (just save the current location to the stack compared to JMP)
The operation is as follows:
1) (SP) = (sp)-2
((ss) *16+ (sp)) = (IP)
2) (IP) = (IP) + 16-bit displacement

Call far PTR designator: remote transfer
1) (SP) = (sp)-2
((ss) *16+ (sp)) = (CS)
(sp) = (sp)-2
((ss) *16+ (sp)) = (IP)
2) (CS) = Segment address where the label is located
(IP) = offset address where the label is located

Call 16-bit register
(sp) = (sp)-2
((ss) *16+ (sp)) = (IP)
(IP) = (16-bit register)
Equivalent:
Push IP
JMP 16-bit registers

The call directives that transfer addresses in memory have two forms:
Call word PTR memory cell address near transfer
Call DWORD PTR memory Unit address far transfer

Mul instruction: Multiplication instruction
Note: Multiplying by two numbers is either 8-bit or 16-bit
8-bit results: in AX
16-bit results: DX High and AX status