Multiplication Table Example

Let's write a simple application This prompts the user for an integer, multiplies it by ascending
Powers of 2 (from + to) using bit shifting, and redisplays each product with leading padded
Spaces. We'll use C + + for the input-output. The assembly language module would contain calls
To three functions written in C + +. The program is launched from C + +.
Assembly Language Module
The assembly language module contains one function, named displaytable. It calls a C + +
function named Askforinteger that inputs a integer from the user. It uses a loop to repeatedly
Shift an integer named Intval to the left and display it by calling Showint.

;ASM function called from C + +INCLUDE Irvine32.Inc;External C + + functions:askforinteger PROTO cshowint PROTO C,Value:Sdword,Outwidth:DWORD;newLine PROTO COut_width =8Ending_power =Ten. Dataintval DWORD?. Code;---------------------------------------------settextoutcolor PROC C,Color:DWORD;;sets the text colors and clears the console;window. Calls Irvine32 library functions.;---------------------------------------------movEax,colorPagerSetTextColorPagerCLRSCRretSettextoutcolor ENDP;---------------------------------------------displaytable PROC C;;Inputs an integer n and displays a;multiplication table ranging from n * 2^1;To N * 2^10.;----------------------------------------------INVOKE Askforinteger;Call C + + functionmovIntval,eax;Save the integermovEcx,ending_power;Loop CounterL1: PushEcx;Save Loop CounterSHLIntval,1 ;Multiply by 2INVOKE showint,intval,out_width;INVOKE newLine; output cr/lfPopEcx;Restore Loop counterLoop L1retdisplaytable endpend

In displaytable, ECX must is pushed and popped before calling Showint and NewLine because
Visual C + + functions do no T save and restore general-purpose registers. The Askforinteger
function returns its result in the EAX register.
Displaytable is not required to use INVOKE when calling the C + + functions. The same
result could is achieved using PUSH and call instructions. This is the Showint
would look:

Push ; push last argument first Push intval Pager ; Call the function add ESP,8; Clean up stack

You must follow the C language calling convention, which arguments is pushed on the
Stack in reverse order and the caller are responsible for removing arguments from the stack after
The call.

C + + Startup program
Let's look at the C + + module, starts the program. Its entry point is main (), ensuring the execution
of required C + + language initialization code. It contains function prototypes for the external
assembly language procedure and the three exported functions:

//main.cpp//demonstrates function calls between a C + + program//and an external assembly language module.#include <iostream>#include<iomanip>using namespacestd;extern "C" {//external ASM procedures:voiddisplaytable ();voidsettextoutcolor (unsigned color);//local C + + functions:intAskforinteger ();voidShowint (intValueintwidth);}//Program Entry PointintMain () {Settextoutcolor (0x1E);//Yellow on BlueDisplaytable ();//Call ASM procedurereturn 0;}//Prompt the user for an integer.intAskforinteger () {intN;cout<<"Enter An integer between 1 and 90,000:"; Cin>>N;returnN;}//Display A signed integer with a specified width.voidShowint (intValueintwidth) {cout<< setw (width) <<value;}

Building the Project our Web site (www.asmirvine.com) have a tutorial for Building combined
c++/assembly Language projects in Visual Studio.

Program output This is sample output generated by the multiplication Table
The user enters 90,000:

Multiplication Table Example