Operating Systems: History Pre 1950 : the very first electronic computers valves and relays no OS single program with dedicated function Pre 1960 : stored program valve machines single job at a time OS just consists of a program loader program CPU printer

Operating Systems: History 1960: transistor machines example: DEC PDP-8 first Edinburgh Univ. computer, 1965 4K 12-bit words of magnetic core memory; 1.5sec cycle time RIM loader read in Binary loader Binary loader read in executable from paper tape a primitive BIOS user program drives I/O devices directly usually by polling interrupts also possible ‘walk up and use’ computer illustrates ‘data rate mismatch’ problem

Operating Systems: History Post 1960 : Batch systems on mainframe computers collections of jobs made up into a batch example: IBM 1401/7094 card decks spooled onto magnetic tape and from tape to printer example: English Electric Leo KDF9 first Edinburgh Univ. mainframe, 1968 32K 48-bit words, 2sec cycle time punched paper-tape input ‘walk-up’ service or spooling via mag tape

Operating Systems: History OS consisted of an input/output system for reading and writing magnetic tapes and a command interpreter for JCL on cards speed mismatch problem reduced with fast mag tape but not removed pipelining allowed next job to be read in whilst results of previous job being written to mag tape

Operating Systems: History 1965: Multiple Job Stream Batch Systems several jobs resident in memory together OS job 1 job 2 job 3 a multiprogramming OS CPU switched around the jobs in turn I/O delays overlapped with other running jobs jobs stay resident until finished

Operating Systems: History IBM MFT - ‘Multiprogramming with Fixed Tasks’ fixed partition boundaries IBM MVT - ‘Multiprogramming with Variable Tasks’ dynamic partition sizes and positions OS scheduled jobs to minimise memory wastage

Operating Systems: History example: Manchester University ATLAS, 1963 32kwords 48-bit memory 1sec cycle time multiprogramming batch system used remotely by Edinburgh Univ. via off-line paper-tape Problems introduced by multiprogramming: jobs had to run at different places in memory inefficient use of expensive memory one job could interfere with another e.g. overwrite other jobs memory jobs could clash over use of I/O devices

Operating Systems: History Overcome by using: relocating linkers and loaders hardware relocation base and limit registers read/write/execute protected access OS controlled access to I/O devices Virtual memory architectures pages and demand-paging invented in Manchester and used first on ATLAS 512 word pages + swap disc segmentation came later

Operating Systems: History 1970: Multi-Access Interactive Time-Sharing Systems powerful machines very expensive need to share use between many users simultaneous interactive use new OS and software technology for time-sharing virtual memory pages and segments processes with a continuing existence, not just for life of job execution memory resident, swapped out to disc, blocked, waiting etc. command interpreters, on-line editors file systems, back-up and archiving TTY terminals - no VDUs until later still stand-alone - no networking

Various Development Projects Operating Systems: History Various Development Projects Project MAC at MIT on IBM 7094, 1966 MULTICS by a consortium on GE645, 1969 EMAP in Edinburgh University on EEC 4-75, 1970 joint project with ICL 4-75: 1Mb memory, 4kb pages and 64kb segments 50 simultaneous users used in Edinburgh until 1989 ported onto ICL 2900 in mid-1970s 100 users dual processor version final port onto NEC (IBM 370 clone) 100s of users overtaken by UNIX-based systems

Operating Systems: History Mini-computer systems DEC VAX (VMS Operating System), Prime, Wang, Interdata, . . . . . . . . between mainframes and workstations in cost and performance Workstation systems increasingly cost-effective since 1980 Sun, IBM PC, Apple Mac Networks of workstations ethernet, token rings etc. Parallel systems large numbers of loosely connected machines only a minimal OS in each usually a separate front-end machine running a normal OS for I/O examples: Connection Machine, Cray T3E in EPCC etc.