Using assembly language in C++ (Visual C++ Express Edition)

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Randell Bailey
7 years ago
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1 Using assembly language in C++ (Visual C++ Express Edition) Copyright 2007 by Barry B. Brey Most applications written today for C++ are developed in Visual Studio using the Express Edition, which is free from Microsoft. Since most applications are written for a PC using Windows, the application is usually a managed application. Managed applications do not allow assembly language. The question is how to embed assembly language into a managed application. If the assembly language functions are placed before the main class in the application it will be accepted and used by the compiler. Apparently the compiler does not switch to the managed mode until it finds the main Form in the application. This can be seen in the example program that follows where a single assembly language function exisits before the Form1 class. One other change is required. In the project properties, under general, the common runtime support must be changed to /CLR from the default setting of /CLR:PURE for it to compile successfully. The default /CLR:PURE sets the compiler to compile only a managed application and the /CLR informs the compiler to start in unmanaged mode before switching to managed mode for the main Form. This creates a section for the assembly code. The simple application that follows illustrates a mixed language program using the inline assembler to add assembly language to a managed C++ program in Visual C++ Express. The application converts an unsigned decimal number into a result that appears in any radix (number base) from 2 to 36. It does not protect against typing a radix of 0, 1, or greater than 36, but this is easy to add. The decimal number must be between 0 and 4 billion. If you examine the assembly language function you might notice that the return is missing, this is allowed and to find out why it functions read my 8 th edition Pentium 4 textbook (Chapter 7) to learn why.

2 #pragma once namespace FirstApp using namespace System; using namespace System::ComponentModel; using namespace System::Collections; using namespace System::Windows::Forms; using namespace System::Data; using namespace System::Drawing; assembly language code placed here short Adjust(short n) _asm mov ax,n add ax,30h cmp ax,39h jle later add ax,7 later: / <summary> / Summary for Form1 / / WARNING: If you change the name of this class, you will need to change the 'Resource File Name' property for the managed resource compiler tool associated with all.resx files this class depends on. Otherwise, the designers will not be able to interact properly with localized resources associated with this form. / </summary> managed mode starts here public ref class Form1 : public System::Windows::Forms::Form public: Form1(void) InitializeComponent(); TODO: Add the constructor code here protected: / <summary> / Clean up any resources being used. / </summary> ~Form1() if (components) delete components; private: System::Windows::Forms::Button^ button1; private: System::Windows::Forms::Label^ label1; private: System::Windows::Forms::Label^ label2;

3 private: System::Windows::Forms::Label^ label3; private: System::Windows::Forms::TextBox^ textbox1; private: System::Windows::Forms::TextBox^ textbox2; private: System::Windows::Forms::TextBox^ textbox3; protected: private: / <summary> / Required designer variable. / </summary> System::ComponentModel::Container ^components; this section is added when the form is drawn in the designer #pragma region Windows Form Designer generated code / <summary> / Required method for Designer support - do not modify / the contents of this method with the code editor. / </summary> void InitializeComponent(void) this->button1 = (gcnew System::Windows::Forms::Button()); this->label1 = (gcnew System::Windows::Forms::Label()); this->label2 = (gcnew System::Windows::Forms::Label()); this->label3 = (gcnew System::Windows::Forms::Label()); this->textbox1 = (gcnew System::Windows::Forms::TextBox()); this->textbox2 = (gcnew System::Windows::Forms::TextBox()); this->textbox3 = (gcnew System::Windows::Forms::TextBox()); this->suspendlayout(); button1 this->button1->location = System::Drawing::Point(191, 31); this->button1->name = L"button1"; this->button1->size = System::Drawing::Size(75, 28); this->button1->tabindex = 0; this->button1->text = L"Convert"; this->button1->usevisualstylebackcolor = true; this->button1->click += gcnew System::EventHandler(this, &Form1::button1_Click); label1 this->label1->autosize = true; this->label1->location = System::Drawing::Point(38, 102); this->label1->name = L"label1"; this->label1->size = System::Drawing::Size(85, 13); this->label1->tabindex = 1; this->label1->text = L"Decimal Number"; label2 this->label2->autosize = true; this->label2->location = System::Drawing::Point(38, 128); this->label2->name = L"label2"; this->label2->size = System::Drawing::Size(34, 13); this->label2->tabindex = 2; this->label2->text = L"Radix"; label3 this->label3->autosize = true; this->label3->location = System::Drawing::Point(38, 154); this->label3->name = L"label3";

4 this->label3->size = System::Drawing::Size(37, 13); this->label3->tabindex = 3; this->label3->text = L"Result"; textbox1 this->textbox1->location = System::Drawing::Point(124, 99); this->textbox1->name = L"textBox1"; this->textbox1->size = System::Drawing::Size(91, 20); this->textbox1->tabindex = 4; textbox2 this->textbox2->location = System::Drawing::Point(124, 125); this->textbox2->name = L"textBox2"; this->textbox2->size = System::Drawing::Size(91, 20); this->textbox2->tabindex = 5; textbox3 this->textbox3->location = System::Drawing::Point(124, 151); this->textbox3->name = L"textBox3"; this->textbox3->size = System::Drawing::Size(91, 20); this->textbox3->tabindex = 6; Form1 this->autoscaledimensions = System::Drawing::SizeF(6, 13); this->autoscalemode = System::Windows::Forms::AutoScaleMode::Font; this->clientsize = System::Drawing::Size(292, 266); this->controls->add(this->textbox3); this->controls->add(this->textbox2); this->controls->add(this->textbox1); this->controls->add(this->label3); this->controls->add(this->label2); this->controls->add(this->label1); this->controls->add(this->button1); this->name = L"Form1"; this->text = L"Converter"; this->resumelayout(false); this->performlayout(); #pragma endregion this is where all the work occurs when Convert is clicked private: System::Void button1_click(system::object^ sender, System::EventArgs^ e) String^ result = ""; try check numbers and catch errors unsigned int number = Convert::ToUInt32(textBox1->Text); unsigned int radix = Convert::ToUInt32(textBox2->Text); do-while takes care of the 0 number case do do all the work here temp = (Char)Adjust(number % radix) + result; number /= radix; while (number!= 0);

5 ; textbox3->text = result; catch (...) catch any error MessageBox::Show("The inputs must be integers!");

Systems Programming & Scripting

Systems Programming & Scripting Lecture 6: C# GUI Development Systems Prog. & Script. - Heriot Watt Univ 1 Blank Form Systems Prog. & Script. - Heriot Watt Univ 2 First Form Code using System; using System.Drawing;