In less than 15 years, Bill Gates has built up his own company from scratch and turned it into a computer giant.

giant 的本义是"巨人"，在这里用作比喻意义，指"规模庞大、影响力巨大的企业或组织"。在商业语境中，computer giant 指的是"计算机行业的巨头企业"，即在该领域占据主导地位的大型公司。