Legacy technologies still in high demand todayIf it ain't broke, don't fix it, as the saying goes. While technology continues to evolve and new languages and technologies like Ruby, Hadoop and cloud containers dominate headlines, proven legacy solutions continue to work quietly behind the scenes, powering much of the digital world. Here are five legacy technologies and skills we still rely on in 2015.\nRelated Story: How legacy technology is creating the next skills gapCOBOLImage by ThinkstockEnd-users interact with COBOL-based systems and solutions much more often that you might think, says Ed Airey, product marketing director for COBOL solutions at application modernization and maintenance firm MicroFocus. Banking, insurance and even air and rail travel solutions that are customer-facing are often COBOL-based, because the language excels at both exact computation and at handling large volumes of data efficiently, says Airey."COBOL excels at processing large volumes of data, which is why it's used in industries that still perform what's called 'batch processing,'" says Airey. The Federal Reserve Bank, credit card companies and the IRS all use COBOL-based systems to process large numbers of transactions at one time. In addition to these use cases, COBOL's used for security and screening purposes; to run background checks, for immigration and border protection and to process information against terrorist watch lists, for example.MainframesImage by ThinkstockMost of these large-scale computing systems were developed in the 1960s, but use and architecture of big iron, as they're affectionately called, continue to evolve. Their stability and reliability allow mainframes to run practically uninterrupted for decades. Industries such as retail, banking, financial services, logistics and manufacturing all rely heavily on mainframe technology and architecture, says Craig O'Malley, CEO of mainframe solutions firm Compuware."Mainframes still dominate many back-end processing systems. This is the best, fastest, most economical system for what it does; and it's not just for batch processing, not just fast access to old data, but mainframes are unparalleled in their ability to handle big data throughput," O'Malley says.CImage by ThinkstockOriginally developed by Dennis Ritchie at Bell Labs between 1969 and 1973, C is one of the most widely used programming languages of all time. In fact, many later languages like C++, Python, Perl, Java and PHP have borrowed many of their basic features from C.The language is widely used in system programming, including implementing operating systems and embedded systems. It has found its way into application software for systems as large as supercomputers and as small as embedded systems. C also forms the foundation for some operating systems, including Unix.FortranImage by ThinkstockThe language formerly known as FORTRAN, for Formula Translation, is a mainframe assembly language that has been in use almost continuously since its development by IBM in the 1950s - you've probably seen pictures of the punch-cards that were used to deliver programming instructions.It's been called the "mother tongue of scientific computing," and was developed by Big Blue to speed scientific and engineering applications on massive supercomputers. It is used today in the areas of weather forecasting, fluid dynamics, computational physics and in other areas of high-performance computing. The next revision of Fortran, Fortran 2015, is currently in the works, and is expected in 2016.JavaImage by ThinkstockTechnically, Java's not a legacy technology, but the language is celebrating its 20th birthday this year. Java was developed by James Gosling at Sun Microsystems in 1995 and was designed so that developers could "write once, run anywhere," without recompilation specific to platform.Despite its age, the language remains near the top of Tiobe Software's Programming Community Index, which measures the popularity of programming languages and can help developers decide if their skills are current, or if they need further training. With approximately nine million developers, Java remains one of the most popular programming languages of all time, and its most common use is in building client-server web applications.