.cpp

case SC_Open:
{
    int filename_ptr = machine->ReadRegister(4);
    int len = 150;
    char *filename = new char[len];

    int *c = new int;
    if (!machine->ReadMem(filename_ptr, 1, c))  // could not read char
        return;

    // int i = 0;
    // while (i < len-1)
    for (int i = 0; i < len-1; ++i,++filename_ptr) {
        filename[i] = *c;
        // ++i;
        // ++filename_ptr;
        if (!machine->ReadMem(filename_ptr, 1, c))  // could not read char
            return;
        
        if ((char) *c == '\0')   // string has ended
            break;
    }
    filename[i] = '\0';

    OpenFile *f = fileSystem->Open(filename);
    int file_id;

    printf("%s file opened", filename);
    delete[] filename;

    if (f)
        file_id = currentThread->space->fileT->addFile(f);

    machine->WriteRegister(2, file_id); // return value

    int pc;
    pc = machine->ReadRegister(PCReg);
    machine->WriteRegister(PrevPCReg, pc);
    pc = machine->ReadRegister(NextPCReg);
    machine->WriteRegister(PCReg, pc);
    pc += 4;
    machine->WriteRegister(NextPCReg, pc);

    break;
}
case SC_Close:
{
    int file_id = machine->ReadRegister(4);

    OpenFile *f = currentThread->space->fileT->getFile(file_id);

    currentThread->space->fileT->removeFile(file_id);
    currentThread->space->fileT->printTable();

    printf("%i file closed\n", file_id);

    int pc;
    pc = machine->ReadRegister(PCReg);
    machine->WriteRegister(PrevPCReg, pc);
    pc = machine->ReadRegister(NextPCReg);
    machine->WriteRegister(PCReg, pc);
    pc += 4;
    machine->WriteRegister(NextPCReg, pc);

    break;
}
case SC_Read:
{
    int buff = machine->ReadRegister(4);    // write into this
    int len = machine->ReadRegister(5);     // read this much
    int fid = machine->ReadRegister(6);     // read from this
    int len_read = 0;

    if (fid == ConsoleOutput)
        return;

    char *str = new char[len+1];

    if (fid == ConsoleInput) {
        fgets(str, len+1, stdin);
        len_read = strlen(str);
    }
    else {
        OpenFile* f = currentThread->space->fileT->getFile(fid);
        if (f)
            len_read = f->Read(str, len);
        else
            printf("Bad OpenFileId passed to Read\n");
    }

    // int i = 0;
    // while (i < len+1)
    for (int i = 0; i < len+1; ++i,++buff) {
        if (!machine->WriteMem(buff, 1, (int) str[i]))
            return;
        // i++;
        // buff++;
    }

    machine->WriteRegister(2, len_read); // return value

    int pc;
    pc = machine->ReadRegister(PCReg);
    machine->WriteRegister(PrevPCReg, pc);
    pc = machine->ReadRegister(NextPCReg);
    machine->WriteRegister(PCReg, pc);
    pc += 4;
    machine->WriteRegister(NextPCReg, pc);

    break;
}
case SC_Write:
{
    int buff = machine->ReadRegister(4);    // write into this
    int len = machine->ReadRegister(5);     // read this much
    int fid = machine->ReadRegister(6);     // read from this

    char *str = new char[len+1];

    int *c = new int;
    if (!machine->ReadMem(buff, 1, c))  // could not read char
        return;

    // int i = 0;
    // while (i < len)
    for (int i = 0; i < len; ++i,++buff) {
        str[i] = *c;
        // i++;
        // buff++;
        if (!machine->ReadMem(buff, 1, c))  // could not read char
            return;
    }   
    str[i] = '\0';

    if (fid == ConsoleInput)
       return;
    else if (fid == ConsoleOutput)
        printf("%s\n", str);
    else {
        OpenFile* f = currentThread->space->fileT->getFile(fid);
        if (f)
            int flag = f->Write(str, len);
        else {
            printf("%s", "Bad OpenFileId passed to Write\n");
            return;
        }
    }

    int pc;
    pc = machine->ReadRegister(PCReg);
    machine->WriteRegister(PrevPCReg, pc);
    pc = machine->ReadRegister(NextPCReg);
    machine->WriteRegister(PCReg, pc);
    pc += 4;
    machine->WriteRegister(NextPCReg, pc);

    break;
}
case SC_Join:
{
    int id = machine->ReadRegister(4);
    int s = 0;
    Thread* t = scheduler->getProcess(id);
    if (t)
        s = t->join();

    machine->WriteRegister(2, s); // return value

    int pc;
    pc = machine->ReadRegister(PCReg);
    machine->WriteRegister(PrevPCReg, pc);
    pc = machine->ReadRegister(NextPCReg);
    machine->WriteRegister(PCReg, pc);
    pc += 4;
    machine->WriteRegister(NextPCReg, pc);

    break;
}