Must comment on the code at every "/* Comment Here */" section about what the code is doing.

/* Comment Here */ public VM() { // create the page table pageTable = new PageTableEntry[PAGE_TABLE_ENTRIES]; for (int i = 0; i < PAGE_TABLE_ENTRIES; i++) pageTable[i] = new PageTableEntry();

// create the TLB TLB = new TLBEntry[TLB_SIZE]; for (int i = 0; i < TLB_SIZE; i++) TLB[i] = new TLBEntry();

// allocate the physical memory physicalMemory = new Frame[NUMBER_OF_FRAMES]; for (int i = 0; i < NUMBER_OF_FRAMES; i++) physicalMemory[i] = new Frame();

// initialize the next frame number nextFrameNumber = 0;

// initialize the next available entry in the TLB nextTLBEntry = 0;

// allocate a temporary buffer for reading in from disk buffer = new byte[PAGE_SIZE];

// initialize the statistics counters pageFaults = 0; TLBHits = 0; }

/* Comment Here */ public int getNextFrame() { return nextFrameNumber++; }

/* Comment Here */ public int checkTLB(int pageNumber) { int frameNumber = -1;

/* Comment Here */ for (int i = 0; i < TLB_SIZE; i++) { if (TLB[i].checkPageNumber(pageNumber)) { frameNumber = TLB[i].getFrameNumber(); TLBHits++;

break; } }

return frameNumber; }

public void setTLBMapping(int pageNumber, int frameNumber) { // establish the mapping TLB[nextTLBEntry].setMapping(pageNumber, frameNumber);

/* Comment Here */ nextTLBEntry = (nextTLBEntry + 1) % TLB_SIZE; }

public int getPhysicalAddress(int virtualAddress) throws java.io.IOException { // determine the page number pageNumber = getPageNumber(virtualAddress); //System.out.println("Page number = " + pageNumber);

// determine the offset offset = getOffset(virtualAddress); //System.out.println("offset = " + offset);

/* Comment Here */ if ( (frameNumber = checkTLB(pageNumber)) == -1 ) { /** TLB Miss **/ // Check the page table if (pageTable[pageNumber].getValidBit() == true) { /** Page Table Hit **/ frameNumber = pageTable[pageNumber].getFrameNumber(); } else { /** Page Fault **/

// get a free frame frameNumber = getNextFrame();

/* Comment Here */

// seek to the appropriate page in the BACKING_STORE file disk.seek(pageNumber * PAGE_SIZE); // read in a page-size chunk from BACKING_STORE // into a temporary buffer disk.readFully(buffer);

// copy the contents of the buffer // to the appropriate physical frame physicalMemory[frameNumber].setFrame(buffer);

// now establish a mapping // of the frame in the page table pageTable[pageNumber].setMapping(frameNumber);

pageFaults++; //System.out.print(" * "); }

// lastly, update the TLB setTLBMapping(pageNumber, frameNumber); }

public byte getValue(int physicalAddress) throws java.io.IOException { /* Comment Here */ return physicalMemory[((physicalAddress & 0x0000ff00) >> 8)].readWord(physicalAddress & 0x000000ff);