of computer games were created for mainframe and minicomputer systems, but these failed to achieve wide distribution due to the continuing scarcity of computer resources, a lack of sufficiently trained programmers interested in crafting entertainment products, and the difficulty in transferring programs between computers in different geographic areas. By the end of the 1970s, however, the situation had changed drastically. The BASIC and C high-level programming languages were widely adopted during the decade, which were more accessible than earlier more technical languages such as FORTRAN and COBOL, opening up computer game creation to a larger base of users. With the advent of time-sharing, which allowed the resources of a single mainframe to be parceled out among multiple users connected to the machine by terminals, computer access was no longer limited to a handful of individuals at an institution, creating more opportunities for students to create their own games. Furthermore, the widespread adoption of the PDP-10, released by Digital Equipment Corporation (DEC) in 1966, and the portable UNIX operating system, developed at Bell Labs in 1971 and released generally in 1973, created common programming environments across the country that reduced the difficulty of sharing programs between institutions. Finally, the founding of the first magazines dedicated to computing like Creative Computing (1974), the publication of the earliest program compilation books like 101 BASIC Computer Games (1973), and the spread of wide-area networks such as the ARPANET allowed programs to be shared more easily across great distances. As a result, many of the mainframe games created by college students in the 1970s influenced subsequent developments in the video game industry in ways that, Spacewar! aside, the games of the 1960s did not. In the arcade and on home consoles, fast-paced action and real-time gameplay were the norm in genres like racing and target shooting. On the mainframe, however, such games were generally not possible due both to the lack of adequate displays (many computer terminals continued to rely on teletypes rather than monitors well into the 1970s and even most CRT terminals could only render character-based graphics) and insufficient processing power and memory to update game elements in real time. While 1970s mainframes were more powerful than arcade and console hardware of the period, the need to parcel out computing resources to dozens of simultaneous users via time-sharing significantly hampered their abilities. Thus, programmers of mainframe games focused on strategy and puzzle-solving mechanics