Compilador Java Simpletron Curso Ciência da Computação
Prof. Chau S. Shia (Noboru)
import java.awt.*;
import java.awt.event.*;
import java.text.DecimalFormat;
import javax.swing.*;
public class Simpletron extends JApplet implements ActionListener
{
// Define 100 slot memory and the accumulator
int instruction_count = 0;
int current_instruction = 0;
boolean has_halted = false;
double accumulator = 0.0;
double memory[] = new double[100];
String instructions[] = new String[100];
// Define all optcodes
final int READ = 10;
final int WRITE = 11;
final int LOAD = 20;
final int STORE = 21;
final int ADD = 30;
final int SUBTRACT = 31;
final int MULTIPLY = 33;
final int DIVIDE = 32;
final int HALT = 43;
// Define all GUI components
JButton addButton, nextButton, executeButton, doneButton;
JTextArea codeArea;
public void init()
{
// Get applets content pane
Container container = getContentPane();
container.setLayout(new FlowLayout());
// Setup user interface buttons
addButton = new JButton("Add");
addButton.addActionListener(this);
container.add(addButton);
nextButton = new JButton("Next");
nextButton.setEnabled(false);
nextButton.addActionListener(this);
container.add(nextButton);
executeButton = new JButton("Execute");
executeButton.setEnabled(false);
executeButton.addActionListener(this);
container.add(executeButton);
Compilador Java Simpletron Curso Ciência da Computação
Prof. Chau S. Shia (Noboru)
doneButton = new JButton("Done");
doneButton.addActionListener(this);
container.add(doneButton);
// Setup the code/output area
codeArea = new JTextArea(20, 30);
codeArea.setText("*** Welcome to Simpletron ***\n" +
"*** Please enter your program one instruction\t***\n" +
"*** at a time by clicking the Add button. When\t***\n" +
"*** you are finished, click Done and then Exe-\t***\n" +
"*** cute. You may click the Next button to st-\t***\n" +
"*** ep through your program.\t\t***\n\n");
codeArea.setEditable(false);
// Setup scroll bar for the code area
JScrollPane scrollPane = new JScrollPane(codeArea);
container.add(scrollPane);
}
public void actionPerformed(ActionEvent event)
{
// Determine which button was clicked and
// perform an action accordingly
if (event.getSource() == addButton)
{
// Display an input dialog to let the user input
// an instruction and append to the instructions list
String instruction = JOptionPane.showInputDialog("Enter an Instruction:");
// Check for valid user input
if (instruction.length() == 0 || instruction.length() < 4 || instruction.length() > 4)
{
JOptionPane.showMessageDialog(null, "Your instruction was invalid.",
"Failed", JOptionPane.ERROR_MESSAGE);
return;
}
else
instructions[instruction_count] = instruction;
// Append the instruction to the code area
codeArea.append(formatNumber(instruction_count) + " ? +" + instruction +
"\n");
instruction_count++;
}
else if (event.getSource() == nextButton)
{
// Take the current instruction and send it
// through the parser, then increment
Compilador Java Simpletron Curso Ciência da Computação
Prof. Chau S. Shia (Noboru)
if (current_instruction <= instruction_count)
{
parse(instructions[current_instruction]);
current_instruction++;
}
else
{
// Since the user has not stopped the program
// and there are no more instructions to execute
// we will send a halt for them
parse("4300");
}
}
else if (event.getSource() == executeButton)
{
// Execute the first instruction and change the
// buttons properties
nextButton.setEnabled(true);
executeButton.setText("Executing...");
executeButton.setEnabled(false);
codeArea.append("\n*** Executing Program ***\n\n");
parse(instructions[current_instruction]);
current_instruction++;
}
else // if getSource is doneButton
{
// Enable and disable buttons accordingly
executeButton.setEnabled(true);
addButton.setEnabled(false);
doneButton.setEnabled(false);
}
}
public String formatNumber(int number)
{
if (number < 10)
return "0" + number;
else
return Integer.toString(number);
}
public void parse(String instruction)
{
// Split instruction up into two parts
int optcode = Integer.parseInt(instruction.substring(0, 2));
int operand = Integer.parseInt(instruction.substring(2, 4));
// Figure out the optcode and perform the specified action
switch (optcode)
{
Compilador Java Simpletron Curso Ciência da Computação
Prof. Chau S. Shia (Noboru)
case READ:
// Read integer input from user and store at memory location
memory[operand] = Double.parseDouble(JOptionPane.showInputDialog("Enter
an integer:"));
codeArea.append("Instruction " + formatNumber(current_instruction) + ":
READ " + formatNumber(operand) + "\n");
break;
case WRITE:
// Display the value of the specified memory location
JOptionPane.showMessageDialog(null, "Result: " + memory[operand], "Result",
JOptionPane.PLAIN_MESSAGE);
codeArea.append("Instruction " + formatNumber(current_instruction) + ":
WRITE " + formatNumber(operand) + "\n");
break;
case LOAD:
// Load the data from the specified memory location into the accumulator
accumulator = memory[operand];
codeArea.append("Instruction " + formatNumber(current_instruction) + ":
LOAD " + formatNumber(operand) + "\n");
break;
case STORE:
// Store the value of the accumulator in the specified memory location
memory[operand] = accumulator;
codeArea.append("Instruction " + formatNumber(current_instruction) + ":
STORE " + formatNumber(operand) + "\n");
break;
case ADD:
// Add the accumulator to the specified memory location and store the
// result back in the accumulator
accumulator += memory[operand];
codeArea.append("Instruction " + formatNumber(current_instruction) + ": ADD
" + formatNumber(operand) + "\n");
break;
case SUBTRACT:
// Subtract the accumulator to the specified memory location and store the
// result back in the accumulator
accumulator -= memory[operand];
codeArea.append("Instruction " + formatNumber(current_instruction) + ":
SUBTRACT " + formatNumber(operand) + "\n");
break;
case MULTIPLY:
// Multiply the accumulator to the specified memory location and store the
// result back in the accumulator
accumulator *= memory[operand];
codeArea.append("Instruction " + formatNumber(current_instruction) + ":
MULTIPLY " + formatNumber(operand) + "\n");
break;
case DIVIDE:
// Check to see if the user tried to divide by zero
if (accumulator == 0 || memory[operand] == 0)
Compilador Java Simpletron Curso Ciência da Computação
Prof. Chau S. Shia (Noboru)
{
// if they have, jump to the last instruction
current_instruction = instruction_count;
codeArea.append("\n*** Fatal Error: Division by Zero at Instruction " +
formatNumber(current_instruction) + " ***\n\n");
}
else
{
// Divide the accumulator to the specified memory location and store the
// result back in the accumulator
accumulator /= memory[operand];
codeArea.append("Instruction " + formatNumber(current_instruction) + ":
DIVIDE " + formatNumber(operand) + "\n");
}
break;
case HALT:
// Simply modify some widget properties and output
// some messages to the user
nextButton.setEnabled(false);
executeButton.setText("Executed");
codeArea.append("Instruction " + formatNumber(current_instruction) + ":
HALT " + formatNumber(operand) + "\n" +
"\n*** Program Terminated ***\n");
break;
}
}
}
<html>
<applet code="Simpletron.class" height="375" width="360">
</applet>
</html>