请帮忙分析一下这三个英语句子的结构

MITS was very interested in seeing their BASIC.
这一句话是主谓宾结构的一般句，MITS是主语，was very interested in 是一个短语做谓语，seeing their BASIC是动词分词做宾语；
So，Gates and Allen began working feverishly on the BASIC they had promised.
Gates and Allen 是主语，began working 是谓语，feverishly 是副词修饰谓语began working， on the BASIC是宾语补足语，they had promised 是一个宾语从句，从句的先行词是BASIC；
The code for the program was left mostly up to Bill Gates while Paul Allen began working on a way to stimulate the Altair.
这句是复合句，两个句子用while连接。

seeing/working/working 都是动名词,分别作in/began/began的宾语.

第一句为一般过去式
第二句为过去完成式
第三句为被动语态

1，（MITS宾语） （was系动词，与后面interested in形成语法结构） （very形容词） interested in （seeing谓语） （their主语) BASIC. （本句为倒装句，过去式）
2，So，（Gates and Allen 主语）（began working 谓语）（feverishly形容词 ）（on介词） （the BASIC 宾语）（省略that）（they had promised宾语从句=they had promised the work on the BASIC ）.
3,(The code for the program 表语)（was系动词）（ left 动词）（mostly 形容词 ）（up to与前面的left 连用，为 介词短语）（Bill Gates 主语）（while连