algorithm

begin
read first input line
if OPCODE = 'START' then
    begin
        save #[OPERAND] as starting address
        initialize LOCCTR to starting address
        write line to intermediate fileread next input line
    end
else initialize LOCCTR to 0
while OPCODE < > 'END' do
    begin
        if this is not a comment line then
            begin
                if there is a symbol in the LABEL field then
                    begin
                        search SYMTAB for LABEL
                        if found then
                            set error flag (dublicate symbol)
                        else insert (LABEL, LOCCTR) into SYMTAB
                    end
                search OPTAB for OPCODE
                if found then
                    add 3 {instruction length} to LOCCTR
                else if OPCODE = 'WORD' then
                    add 3 to LOCCTTR
                else if OPCODE = 'RESW' then
                    add 3 * #[OPERAND] to LOCCTR
                else if OPCODE = 'RESB' then
                    add #[OPERAND] to LOCCTR
                else if OPCODE = 'BYTE' then
                    begin
                        find length of constant in bytesadd length to LOCCTR
                    end
                else set error flag {invalid operation code}
            end {if not a comment}
        write line to intermediate file
        read next input line
    end {while}
write last line to intermediate file
save {LOCCTR - starting address} as program length
end {Pass 1}



begin
read first input line {from intermediate file}
if OPCODE = 'START' then
    begin
        write listing lineread next input line
    end
write Header record to object program
initialize first Text record
while OPCODE < > 'END' do
    begin
        if this is not a comment line then
            begin
                ssearch OPTAB for OPCODE
                if found then
                    begin
                        if there is a symbol in OPERAND field then
                            begin
                                search SYMTAB for OPERAND
                                if found then
                                    store symbol value as operand address
                                else
                                    begin
                                        store 0 as operand address
                                        set error flag {undefined symbol}
                                    end
                            end {if symbol}
                        else
                            store 0 as operand address
                        assemble the object code instruction
                    end {if found}
                else if OPCODE = 'BYTE' or 'WORD' then
                    convert constant to object code
                if object code will not fit into the current Text record them
                    begin
                        thie Text record to object program
                        initialize new Text record
                    end
                add object code to Text record
            end {if not comment}
        write listing line
        read next input line
    end {while}
write last Text record to object program
write End record to object program
write last listing line
end {Pass 2}