Evolution of OS Flashcards
From late 1940s to the mid-1950s, programmers interact directly with computer hardware since operating systems (OS) are not yet available.
Serial processing
Computers are run from a console consisting of display lights, toggle switches, an input device, and a printer
Serial processing
Programs in machine code were loaded via input device, such as a
card reader.
Serial processing
Error conditions are indicated by the display lights
Serial processing
If a program executes successfully, the output is printed
Serial processing
Two main problems of Serial processing:
- Scheduling
- Set-up time
Installations used a hardcopy sign-up sheet to reserve computer time. A user could sign up for an allocated block of time, but is unable to maximize the allocation. Thus, resulting in wasted computer processing time.
Scheduling
A single program, called a job, involves numerous sequence set-up processes that involve mounting and dismounting of tapes and setting up card decks. If an error occurred, the user had to go back to the beginning of the setup sequence. Thus, a considerable amount of time was spent in setting up the program before it even runs
Set-up time
To improve processor utilization, the concept of batch operating system was developed in the mid-1950s by General Motors Research Laboratories. It processed jobs in bulk, with predetermined input from files or other data resources.
Simple Batch Systems
The main idea behind batch processing is the utilization of a piece of program known as the
monitor or resident monitor
The main idea behind batch processing is the utilization of a piece of program known as the monitor or resident monitor. The monitor provides automatic job sequencing as indicated by the control cards. If a control card indicates that a program is to be run, the monitor loads the program into memory and transfers control to it. When the program completes, it transfers the control back to the monitor. Then, it reads the next control card, loads the appropriate program, and so on. This cycle is repeated until all control cards are interpreted for the job. [T/F]
True
This kind of operating system is more sophisticated compared to single-programmed systems. Several ready-to-run jobs must be kept in the main memory, requiring some form of memory management.
Multi-programmed Batch Systems
It basically allows the
processor to handle multiple jobs at a time.
Multi-programmed Batch Systems
multiple users simultaneously access the system
through terminals, with the operating system interleaving the execution of each user program in a short burst time or quantum computation.
Time-sharing systems
If there are n number of users actively requesting service at exactly the same time, each user will only be allocated … of the …, excluding the operating system overhead.
1/n | effective compute capacity
