A decent developer is a huge rarity. The problem is not even in the poor knowledge of programming language, but in an integrated approach. The modern developer should not only comprehend, but also integrate modern technologies into their work and be aware of the correlation between innovation and high demand of the computer software. Only this developer will be the most sought after in any company, no matter how many programming languages he/she knows.
Today more than 50 programming languages are being actively used, but the most significant ones can be counted on the fingers of one hand. They constitute the great bulk of the market and bring income to programmers. Following this introduction, we approach the first and the most important skill of any developer.