assembly_tutorial

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%eax Name %ebx %ecx %edx %esx %edi 1 sys_exit int - - - - 2 sys_fork struct pt_regs - - - - 3 sys_read unsigned int char * size_t - - 4 sys_write unsigned int const char * size_t - - 5 sys_open const char * int int - - 6 sys_close unsigned int - - - - Example The following example reads a number from the keyboard and displays it on the screen: section .data ;Data segment userMsg db 'Please enter a number: ' ;Ask the user to enter a number lenUserMsg equ $-userMsg ;The length of the message dispMsg db 'You have entered: ' lenDispMsg equ $-dispMsg section .bss ;Uninitialized data num resb 5 section .text ;Code Segment global main main: ;User prompt mov eax, 4 mov ebx, 1 mov ecx, userMsg mov edx, lenUserMsg int 80h ;Read and store the user input mov eax, 3 mov ebx, 2 mov ecx, num mov edx, 5 ;5 bytes (numeric, 1 for sign) of that information int 80h ;Output the message 'The entered number is: ' mov eax, 4 mov ebx, 1 mov ecx, dispMsg mov edx, lenDispMsg int 80h ;Output the number entered mov eax, 4 mov ebx, 1 mov ecx, num mov edx, 5 int 80h ; Exit code mov eax, 1 mov ebx, 0 int 80h When the above code is compiled and executed, it produces following result: TUTORIALS POINT Simply Easy Learning
Please enter a number: 1234 You have entered:1234 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: CHAPTER 6 Assembly System Calls Sys
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 48: AND AL, 01H ; ANDing with 0000 0001
Page 49 and 50: The TEST Instruction The TEST instr
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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