PrimeraPasada

public static void pass_one( ) {
    // This procedure is an outline of pass one of a simple assembler.
    boolean moreinput = true;
    // flag that stops pass one
    String line, symbol, literal, opcode;
    // fields of the instruction
    int location_counter, length, value, type; // misc. variables
    final int END_STATEMENT = −2;
    // signals end of input
    location_counter = 0;
    initialize_tables( ); // assemble first instruction at 0
    // general initialization
    while (moreinput) {
        line = read_next_line( );
        length = 0;
        type = 0; // more_ input set to false by END
        // get a line of input
        // # bytes in the instruction
        // which type (format) is the instruction
        if (line_is_not_comment(line)) {
            symbol = check_for_symbol(line);
            // is this line labeled?
            if (symbol != null){
                // if it is, record symbol and value
                enter_new_symbol(symbol, location_counter);
            }
            literal = check_for_literal(line);
            // does line contain a literal?
            // if it does, enter it in table
            if (literal != null){
                enter_new_literal(literal);
                }
        }
        // Now determine the opcode type. −1 means illegal opcode.
        opcode = extract_opcode(line);
        // locate opcode mnemonic
        type = search_opcode_table(opcode); // find format, e.g. OP REG1,REG2
        if (type < 0){
            // if not an opcode, is it a pseudoinstruction?
            type = search_pseudo_table(opcode);
        }
        // determine the length of this instruction
        switch(type) {
            case 1: length = get_length_of_type1(line); break;
            case 2: length = get_length_of_type2(line); break;
            // other cases here
        }
        write_temp_file(type, opcode, length, line); // useful info for pass two
        location_counter = location_counter + length;
        // update loc_ ctr
        if (type == END_STATEMENT) {
            // are we done with input?
            more_input = false;
            // if so, perform housekeeping tasks
            rewind_temp_for_pass_two( );
            // like rewinding the temp file
            sort_literal_table( );
            // and sorting the literal table
            remove_redundant_literals( );
            // and removing duplicates from it
        }
    }
}