History of operating systems

Computer operating systems (OSes) provide a set of functions needed and used by most application programs on a computer, and the links needed to control and synchronize computer hardware. On the first computers, with no operating system, every program needed the full hardware specification to run correctly and perform standard tasks, and its own drivers for peripheral devices like printers and punched paper card readers. The growing complexity of hardware and application programs eventually made operating systems a necessity for everyday use. The earliest computers were mainframes that lacked any form of operating system. Each user had sole use of the machine for a scheduled period of time and would arrive at the computer with program and data, often on punched paper cards and magnetic or paper tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a control panel using dials, toggle switches and panel lights. Symbolic languages, assemblers, and compilers were developed for programmers to translate symbolic program-code into machine code that previously would have been hand-encoded. Later machines came with libraries of support code on punched cards or magnetic tape, which would be linked to the user's program to assist in operations such as input and output. This was the genesis of the modern-day operating system; however, machines still ran a single job at a time. At Cambridge University in England the job queue was at one time a string from which tapes attached to corresponding job tickets were hung with stationery pegs. As machines became more powerful the time to run programs diminished, and the time to hand off the equipment to the next user became large by comparison. Accounting for and paying for machine usage moved on from checking the wall clock to automatic logging by the computer.