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After OR -> Operand1: 0111 The OR operation can be used for setting one or more bits. For example, let us assume the AL register contains 0011 1010, you need to set the four low order bits, you can OR it with a value 0000 1111, i.e., FH. OR BL, 0FH ; This sets BL to 0011 1111 Example: The following example demonstrates the OR instruction. Let us store the value 5 and 3 in the AL and the BL register respectively. Then the instruction, OR AL, BL should store 7 in the AL register: section .text global main ;must be declared for using gcc main: ;tell linker entry point mov al, 5 ;getting 5 in the al mov bl, 3 ;getting 3 in the bl or al, bl ;or al and bl registers, result should be 7 add al, byte '0' ;converting decimal to ascii mov [result], al mov eax, 4 mov ebx, 1 mov ecx, result mov edx, 1 int 0x80 outprog: mov eax,1 ;system call number (sys_exit) int 0x80 ;call kernel section .bss result resb 1 When the above code is compiled and executed, it produces following result: 7 The XOR Instruction The XOR instruction implements the bitwise XOR operation. The XOR operation sets the resultant bit to 1, if and only if the bits from the operands are different. If the bits from the operands are same (both 0 or both 1), the resultant bit is cleared to 0. For example, Operand1: 0101 Operand2: 0011 ---------------------------- After XOR -> Operand1: 0110 XORing an operand with itself changes the operand to 0. This is used to clear a register. XOR EAX, EAX TUTORIALS POINT Simply Easy Learning
The TEST Instruction The TEST instruction works same as the AND operation, but unlike AND instruction, it does not change the first operand. So, if we need to check whether a number in a register is even or odd, we can also do this using the TEST instruction without changing the original number. TEST JZ AL, 01H EVEN_NUMBER The NOT Instruction The NOT instruction implements the bitwise NOT operation. NOT operation reverses the bits in an operand. The operand could be either in a register or in the memory. For example, Operand1: 0101 0011 After NOT -> Operand1: 1010 1100 TUTORIALS POINT Simply Easy Learning
Page 1 and 2: Assembly Language Tutorial
Page 3 and 4: ABOUT THE TUTORIAL Assembly Program
Page 5 and 6: Table of Content Assembly Programmi
Page 7 and 8: The XOR Instruction ...............
Page 9 and 10: CHAPTER 1 Assembly Introduction Wha
Page 11 and 12: Main use of hexadecimal numbers in
Page 13 and 14: x: memory address When the processo
Page 15 and 16: Check The netwide assembler (NASM)
Page 17 and 18: ; This program displays a message o
Page 19 and 20: CHAPTER 4 Assembly Memory Segments
Page 21 and 22: CHAPTER 5 Assembly Registers Proces
Page 23 and 24: Control Registers The 32-bit instru
Page 25 and 26: CHAPTER 6 Assembly System Calls Sys
Page 27 and 28: Please enter a number: 1234 You hav
Page 29 and 30: Direct Memory Addressing When opera
Page 31 and 32: int 0x80 ;call kernel mov eax,1 ;sy
Page 33 and 34: Processor uses the little-endian by
Page 35 and 36: CHAPTER 9 Assembly Constants There
Page 37 and 38: The above code replaces PTR by [EBP
Page 39 and 40: dec [value] mov ebx, count inc word
Page 41 and 42: int 0x80 When the above code is com
Page 43 and 44: global main ;must be declared for u
Page 45 and 46: mov [res], ax mov ecx,msg mov edx,
Page 47: AND AL, 01H ; ANDing with 0000 0001
Page 51 and 52: L7: ... CMP is often used for compa
Page 53 and 54: jg _exit mov ecx, [num3] _exit: mov
Page 55 and 56: section .bss num resb 1 mov ecx, nu
Page 57 and 58: Such conversions are however, has a
Page 59 and 60: mov ecx,msg ;message to write mov e
Page 61 and 62: LODS - This instruction loads from
Page 63 and 64: mov ecx, len mov esi, s1 mov edi, s
Page 65 and 66: found! Repetition Prefixes The REP
Page 67 and 68: Example: The following example demo
Page 69 and 70: mov ecx, res mov edx, 1 mov ebx, 1
Page 71 and 72: CHAPTER 18 Assembly Recursion Arecu
Page 73 and 74: CHAPTER 19 Assembly Macros Writing
Page 75 and 76: CHAPTER 20 Assembly File Management
Page 77 and 78: Put the buffer size, i.e., the numb
Page 79 and 80: int 0x80 ;call kernel section .data
Page 81: mov eax, 1 xor ebx, ebx int 80h sec

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