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Operating System

Notes Wallace Eckert and John Mauchly and the EDVAC, developed in 1944-46 by John Von Neumann,
Arthur Burks, and Herman Goldstine (which was the first to fully implement the idea of the

stored program and serial execution of instructions) were designed. The development of EDVAC
set the stage for the evolution of commercial computing and operating system software. The
hardware component technology of this period was electronic vacuum tubes.

The actual operation of these early computers took place without the benefit of an operating
system. Early programs were written in machine language and each contained code for initiating
operation of the computer itself.
The mode of operation was called “open-shop” and this meant that users signed up for computer
time and when a user’s time arrived, the entire (in those days quite large) computer system was
turned over to the user. The individual user (programmer) was responsible for all machine set
up and operation, and subsequent clean-up and preparation for the next user. This system was

clearly inefficient and dependent on the varying competencies of the individual programmer as
operators.

1.5.2 First Generation (1951-1956)

The first generation marked the beginning of commercial computing, including the introduction
of Eckert and Mauchly’s UNIVAC I in early 1951, and a bit later, the IBM 701 which was also

known as the Defence Calculator. The first generation was characterised again by the vacuum
tube as the active component technology.
Operation continued without the benefit of an operating system for a time. The mode was called

“closed shop” and was characterised by the appearance of hired operators who would select the
job to be run, initial program load the system, run the user’s program, and then select another
job, and so forth. Programs began to be written in higher level, procedure-oriented languages,
and thus the operator’s routine expanded. The operator now selected a job, ran the translation
program to assemble or compile the source program, and combined the translated object program
along with any existing library programs that the program might need for input to the linking
program, loaded and ran the composite linked program, and then handled the next job in a
similar fashion.
Application programs were run one at a time, and were translated with absolute computer
addresses that bound them to be loaded and run from these reassigned storage addresses set by
the translator, obtaining their data from specific physical I/O device. There was no provision for

moving a program to different location in storage for any reason. Similarly, a program bound to

specific devices could not be run at all if any of these devices were busy or broken.

The inefficiencies inherent in the above methods of operation led to the development of the
mono-programmed operating system, which eliminated some of the human intervention in
running job and provided programmers with a number of desirable functions. The OS consisted
of a permanently resident kernel in main storage, and a job scheduler and a number of utility
programs kept in secondary storage. User application programs were preceded by control or
specification cards (in those day, computer program were submitted on data cards) which

informed the OS of what system resources (software resources such as compilers and loaders; and
hardware resources such as tape drives and printer) were needed to run a particular application.
The systems were designed to be operated as batch processing system.
These systems continued to operate under the control of a human operator who initiated
operation by mounting a magnetic tape that contained the operating system executable code
onto a “boot device”, and then pushing the IPL (Initial Program Load) or “boot” button to initiate
the bootstrap loading of the operating system. Once the system was loaded, the operator entered
the date and time, and then initiated the operation of the job scheduler program which read
and interpreted the control statements, secured the needed resources, executed the fi rst user

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