Operators in 8086

Operators in 8086
- Operator can be applied in the operand which uses the immediate data/address.
- Being active during assembling and no machine language code is generated.
- Different types of operators are:
1) Arithmetic: + , - , * , /
2) Logical : AND, OR, XOR, NOT
3) SHL and SHR: Shift during assembly
4) [ ]: index
5) HIGH: returns higher byte of an expression
6) LOW: returns lower byte of an expression. E.g. NUM EQU 1374 H
MOV AL HIGH Num ; ( [AL] 13 )
7) OFFSET: returns offset address of a variable
8) SEG: returns segment address of a variable
9) PTR: used with type specifications
BYTE, WORD, RWORD, DWORD, QWORD
E.g. INC BYTE PTR [BX]
10) Segment override
MOV AH, ES: [BX]
11) LENGTH: returns the size of the referred variable
12) SIZE: returns length times type
E.g.:
BYTE VAR DB?
WTABLE DW 10 DUP (?)
MOV AX, TYPE BYTEVAR
; AX = 0001H
MOV AX, TYPE WTABLE
; AX = 0002H
MOV CX, LENGTH WTABLE
; CX = 000AH
MOV CX, SIZE WTABLE
; CX = 0014H

Coding in Assembly language:
Assembly language programming language has taken its place in between the machine
language (low level) and the high level language.
- High level language’s one statement may generate many machine instructions.
- Low level language consists of either binary or hexadecimal operation. One symbolic
statement generates one machine level instructions.
Advantage of ALP
- They generate small and compact execution module.
- They have more control over hardware.
- They generate executable module and run faster.
Disadvantages of ALP:
- Machine dependent.
- Lengthy code
- Error prone (likely to generate errors).
Assembly language features:
The main features of ALP are program comments, reserved words, identifies, statements and
directives which provide the basic rules and framework for the language.
Program comments:
- The use of comments throughout a program can improve its clarity.
- It starts with semicolon (;) and terminates with a new line.
- E.g. ADD AX, BX ; Adds AX & BX