1. 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

2. 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

3. 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

4. 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

5. Operating Systems: History
1965: Multiple Job Stream Batch Systems
several jobs resident in memory together OS
job job 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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.