Compiler, Tools and other files are available from the following sites (links open in an new window): The Win32 - API as.HLP file is available from Borland as a part of the Delphi Help or as a part of the C Help. Message Cracker Wizard 'Message Cracker Wizard is the tool to unleash the power of message crackers: a set of macros that are in the windowsx.h header file of almost every Windows C/C compiler making message handling and processing easier than ever'. Also works with PellesC Win32 wizard! Writing Windows assembly code, especially with MASM, is very easy. It is almost like writing some C code. Give it a chance and I am certain that you won't be disappointed. size='5' Win32 ASM Basics If you are already familiar with assembly language in the windows platform, you may want to skip this section. Introduction to assembly language programming for pentium and RISC processors Dandamudi.pdf Introduction to Python for Econometrics, Statistics and Data Analysis.pdf IPython Interactive Computing and Visualization Cookbook.pdf.

CIS-77 Home http://www.c-jump.com/CIS77/CIS77syllabus.htm

Netwide Assembler. NASM will currently output flat-form binary files, a.out, COFF and ELF Unix object files, and Microsoft 16-bit DOS and Win32 object files. This is the code for an assembly language program that prints Hello world.

Introduction to x86 Assembly Language

1. Advantages of High-Level Languages

• High-level language programs are portable.

  • (Although some programs could still have a few machine-dependent details, they can be used with little or no modifications on other types of machines.)

• High-level instructions:

  • Program development is faster

  • Fewer lines of code

  • Program maintenance is easier

• Compiler translates to the target machine language.

2. Why program in Assembly ?

• There are some disadvantages..

  • Assembly language programs are not portable!

  • Learning the assembly is more difficult than learning Java!

  • Programming in the assembly language is a tedious and error-prone process.

  • High-level languages should be natural preference for common applications.

3. Here is why..

• I just don't consider a utility program that's 4 megabytes big, and contains all sorts of files that the author didn't create, to be really great software.
  Do you?

• Steve Gibson, Gibson Research Corporation.

• Assembly language programs contain only the code that is necessary to perform the given task.

• Assembly gives direct and complete control over system hardware:

  • Writing device drivers.

  • Operating system design.

  • Embedded systems programming, e.g. aviation industry.

  • Writing in-line assembly (mixed-mode) in high-level languages such as C/C++, or hybrid programming in assembly and C/C++.

4. Speed, Efficiency, Debugging, Optimization..

• There are areas where speed is everything, for example, internet data encryption, aircraft navigational systems, medical hardware control..

• There are also areas where space-efficiency is everything: spacecraft control software..

• Understanding disassembly view of an executable program is also useful:

  • for investigating the cause of a serious bugs or crashes that require understanding of memory dumps and disassembled code.

  • for optimizing your code.

  • for practical and educational purposes.

5. Why MASM ?

• The 'granddaddy' of all assemblers for the Intel platform, product of Microsoft.

• Available since the beginning of the IBM-compatible PCs.

• Works in MS-DOS and Windows environments.

• It's free: Microsoft no longer sells MASM as a standalone product.

• Bundled with the Microsoft Visual Studio product.

• Numerous tutorials, books, and samples floating around, many are free or low-cost.

• Steve Hutchessen's www.masm32.com

• MASM32 development environment incorporates MASM assembler and Win32 API tools.

6. Introduction to 80x86 Assembly Language

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• Logic gates are used at the hardware level.

• What is machine language?

• How high-level language concepts, such as if-else statements, are realized at the machine level?

• What about interactions with the operating system functions?

• How is assembly language translated into machine language?

  • These fundamental questions apply to most computer architectures.

  • By using assembly, we gain understanding of how the particular model of computer works.

7. Materials on the Web

• Such secrets have been revealed to me that all I have written now appears of little value.

• St. Thomas Aquinas, December 6, 1273.

• Useful links: Microsoft MASM Programmer's Guide Assembly-Language Development System v6.1, also at another location

  MASM Reference Guide can be downloaded there, too.

• More here: Assembly Technical Documentation in PDF and MS Word format

• Intel and Microsoft MASM 6.1 Documentation

• A web page with a variety of assembler source code

• Intel 80x86 Conditional and Unconditional Branching ExamplesCustom ui editor for mac.

• Intel 80x86 Boolean and Arithmetic Instruction Examples

• You can get Microsoft's Macro Assembler free: download Microsoft Windows Driver Development Kit (DDK), which contains both assembler and linker. Also, download Microsoft's Debugging Tools for Windows 32-bit Version.

• Take a look at Sivarama P. Dandamudi textbook info, Introduction to Assembly Language Programming , From 8086 to Pentium. Homepage includes free downloadable Microsoft assembler, MASM , and student slides.

• Last, but not least, Microsoft Macro Assembler Reference MSDN resource.

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8. Useful books, in no particular order

9. Fundamental Concepts

• CPU registers

• Memory addressing

• Representation of data:

  • numeric formats

  • character strings

• Instructions to operate on 2's complement integers

• Instructions to operate on individual bits

• Instructions to handle strings of characters

• Instructions for branching and looping

• Coding of procedures:

  • transfer of control

  • parameter passing

  • local variables

10. Software Environment

• The tools we will use include:

  • Visual Studio development environment..

    • ..edit, assemble, link, manage projects, debug and disassemble programs.

  • Command-line MASM, Microsoft Macro Assembler..

    • ..produces code for 32-bit flat memory model appropriate to modern Windows.

  • Test-drive fullscreen 32-bit debuggers: OllyDbg, Visual Studio, WinDbg.

  • DUMPBIN: command-line utility that examines binary files and disassembles programs.

11. Runtime Environment

• Program runs on the processor.

• Program uses operating system functions and services.

• Program uses one of the memory models:

  • Real mode flat model, 65,536 bytes of addressable memory (ancient MS-DOS .COM files)

  • Real mode segmented model, 1 megabyte (prime-time MS-DOS)

  • Protected mode flat model, modern Windows and Linux:

    • Addressable Memory: 80486 and Pentium - 4 Gigabytes

    • As far as 32-bit Vista is concerned, the world ends at 4,096 megabytes.

    • A 32-bit program can address up to 4 gigabytes of memory.

12. Assembly and C Code Compared

• Some simple high-level language instructions can be expressed by a single assembly instruction:

13. More Assembly and C Code

• Most high-level language instructions need more than one assembly instruction:

14. Assembly vs. Machine Language

• Assembly Language uses mnemonics, digital numbers, comments, etc.

• Machine Language instructions are just a sequences of 1s and 0s.

• Readability of assembly language instructions is much better than the machine language instructions:

15. Controlling Program Flow

• Just as in high-level language, you want to control program flow.

• The JMP instruction transfers control unconditionally to another instruction.

• JMP corresponds to goto statements in high-level languages:

16. Conditional Jumps

• Conditional jump is taken only if the condition is met.

• Condition testing is separated from branching.

• Flag register is used to convey the condition test result.

• For example:

17. General-Purpose Registers

• Similarly, AL, DL, CL, and BL represent the low-order 8 bits of the registers.

18. Typical Uses of General-Purpose Registers

Register	Size	Typical Uses
EAX	32-bit	Accumulator for operands and results
EBX	32-bit	Base pointer to data in the data segment
ECX	32-bit	Counter for loop operations
EDX	32-bit	Data pointer and I/O pointer
EBP	32-bit	Frame Pointer - useful for stack frames
ESP	32-bit	Stack Pointer - hardcoded into PUSH and POP operations
ESI	32-bit	Source Index - required for some array operations
EDI	32-bit	Destination Index - required for some array operations
EIP	32-bit	Instruction Pointer
EFLAGS	32-bit	Result Flags - hardcoded into conditional operations

19. x86 Registers

• Four 32-bit registers can be used as

  • Four 32-bit registers EAX, EBX, ECX, EDX.

  • Four 16-bit registers AX, BX, CX, DX.

  • Eight 8-bit register AH, AL, BH, BL, CH, CL, DH, DL.

• Some registers have special use..

  • ..ECX for count in LOOP and REPeatable instructions

20. x86 Registers, Cont

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21. x86 Control Registers

• EIP Program counter (Instruction Pointer)

• EFLAGS is set of bit flags:

  • Status flags record status information about the result of the last arithmetic/logical instruction.

  • Direction flag stores forward/backward direction for data copying.

  • System flags store

    • IF interrupt-enable mode

    • TF Trap flag used in single-step debugging.

22. MOV, Data Transfer Instructions

• The MOV instruction copies the source operand to the destination operand without affecting the source.

• Five types of operand combinations are allowed with MOV:

• Note: the above operand combinations are valid for all instructions that require two operands.

23. Ambiguous MOVes: PTR and OFFSET

• For the following data definitions

• The above MOV instructions are ambiguous.

• Not clear whether the assembler should use byte or word equivalent of 100.

• Better:

24. INC and DEC Arithmetic Instructions

• Format:

• Semantics:

• The destination can be 8-bit, 16-bit, or 32-bit operand, in memory or in register.

• No immediate operand is allowed.

• Examples:

25. ADD Arithmetic Instruction

• Format:

• Semantics:

• Examples:

26. ADD vs. INC

• Note that

  is better than

• INC takes less space.

• Both INC and ADD execute at about the same speed.

27. SUB Arithmetic Instruction

• Format:

• Semantics:

• Examples:

28. SUB vs. DEC

• Note that

  is better than

• DEC takes less space.

• Both execute at about the same speed.

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29. CMP instruction

• Format:

• Semantics:

• The destination and source are not altered.

• Useful to test relationship such as < > or = between the two operands.

• Used in conjunction with conditional jump instructions for decision making purposes.

• Examples:

30. Unconditional Jumps

• Format:

• Semantics:

  • Execution is transferred to the instruction identified by the label.

  • Infinite loop example:

31. Conditional Jumps

• Format:

• Semantics:

  • Execution is transferred to the instruction identified by label only if condition is met.

  • Testing for carriage return example:

32. Conditional Jumps, Cont

• Some conditional jump instructions treat operands of the CMP instruction as signed numbers:

33. Conditional Jumps, Cont

• Some conditional jump instructions can also test values of the individual CPU flags:

34. LOOP Instruction

• Format:

• Semantics:

  • Decrements ECX and jumps to target, if ECX > 0

  • ECX should be loaded with a loop count value before loop begins.

35. Logical Instructions

• Format:

• Semantics:

  • Perform the standard bitwise logical operations.

  • Result goes to the destination.

• TEST is a non-destructive AND instruction:

• TEST performs logical AND but the result is not stored in destination (similar to CMP instruction.)

36. Logical Instructions, Cont.

• Example of testing the value in AL for odd/even number:

37. Shift Instructions

• Shift left format:

• Shift right format:

  where count is an immediate value.

• Semantics:

  • Performs left/right bit-shift of destination by the value in count or CL register.

  • CL register contents is not altered.

38. SHL and SHR Shift Instructions

• Bit shifted out goes into the carry flag CF.

• Zero bit is shifted in at the other end:

39. Shift Instructions Examples

• Count is an immediate value:

• Specification of count greater than 31 is not allowed.

• If greater, only the least significant 5 bits are actually used.

• CL version of shift is useful if shift count is known at run time,

  • e.g. when the shift count is a parameter in a procedure call.

• Only CL register can be used.

• Shift count value should be loaded into CL:

40. Rotate Instructions

• Two types of rotate instructions:

  1. Rotate without carry:

     • ROL (ROtate Left)

     • ROR (ROtate Right)

  2. Rotate with carry:

     • RCL (Rotate through Carry Left)

     • RCR (Rotate through Carry Right)

• Rotate instruction operand is similar to shift instructions and supports two versions:

  • Immediate count value

  • Count value is in CL register

41. ROL and ROR, Rotate Without Carry

42. RCL and RCR, Rotate With Carry

43. EQU directive

• EQU directive eliminates hardcoding:

• No reassignment is allowed.

• Only numeric constants are allowed.

• Defining constants has two main advantages:

  1. Improves program readability

  2. Helps in software maintenance.

• Multiple occurrences can be changed from a single place

• The convention is to use all UPPER-CASE LETTERS for names of constants.

44. EQU Directive Syntax

• Assigns the result of expression to name.

• The expression is evaluated at assembly time.

• More examples: