In 1981 Apple computers released this full page advert in the Wall Street Journal aimed at IBM as a tongue in cheek way of saying 'where have you been'. Apple at this time was still a relatively young company but had been in the personal computer market since 1977, whereas IBM was already a multi billion dollar company and much larger than apple, but hadn't entered the personal computer market due to them thinking it wasn't going to be a successful market and would soon die out.
This advert was published the day of IBM publicly announcing they were eventually entering the market with their first PC, and is Apples response to them not thinking it was a stable market. The title alone 'Welcome IBM. Seriously' is a smug patronising statement from Apple, it makes IBM seem like the inferior company, when in fact at the time they were a giant. This was Apples way of setting themselves as the main competitor to IBM in the publics eye 'we look forward to responsible competition in the massive effort to distribute this American technology to the world', belittling IBM they're showing themselves as a technological innovator ahead of even the largest of companies 'when we invented the first computer'. It's subtle statements within what seems a lovely welcome to the market ad that that helps Apple to create an identity larger than the one they already have out of the expense of IBM.
Apple are trying to secure the identity as something they're not, technological innovators and market leaders by targeting the largest company and pointing out the fact they're late to the party, behind the times, slow at reacting but together now that IBM have come to their senses, as the two main competitors they can meet the demand for this growing market, as the rolling quote says 'we look forward to responsible competition in the massive effort to distribute this American technology to the world'