《80x86课程英文版的课件Chapter3ElementsofAssemblyLanguage.ppt

Chapter 3 Elements of Assembly Language How to develop assembly Language Programs Directives in MASM Contents Types and formats of statements in MASM Example program for how to assemble, link, and execute Structure of assembly language program Constant operands (操作数) and instruction operands 3.2 A Complete Example Purpose: prompt for (提示输入) two numbers and then find and display their sum. Pseudocode design for the program Prompt for the first number; Input ASCII characters representing the first number; Convert the characters to a 2’s complement double word Store the first number in memory; Prompt for the second number; Input ASCII characters representing the first number; Convert the characters to a 2’s complement double world Add the first number to the second number; Convert the sum to a string of ASCII characters; Display a label and the characters representing the sum; Structure of the program(2) ExitProcess PROTO NEAR32 stdcall, dwExitCode:DWORD INCLUDE io.h ; header file for input/output cr EQU 0dh ; carriage return character Lf EQU 0ah ; line feed Structure of the program(3) .DATA ; reserve storage for data number1 DWORD ? number2 DWORD ? Structure of the program(4) prompt1 BYTE Enter first number: , 0 prompt2 BYTE Enter second number: , 0 string BYTE 40 DUP (?) label1 BYTE cr, Lf, The sum is sum BYTE 11 DUP (?) BYTE cr, Lf, 0 Template for assembly language 3.1 Assembly Language Statements Length: up to 512 If not enough, use backslash(\) character at the end of a line Comments: Begin with the semicolon(;) and extends until the end of the line Three types of functional assembly language statements Instructions（真指令） Can be translated into machine code( object code) Directives（伪指令） Tell the assembler to take some action , not result in machine code macros（宏） Shorthand for a sequence of other statements Components of a stat