I. Read the text and make the list of key words which can be used to characterize distinctive features of each generation of the operating system.

Operating systems have evolved through a number of distinct phases or generations, which corresponds roughly to the decades.

The 1940’s — First Generations

The earliest electronic digital computers had no operating systems. Machines of that time were so primitive that programs were often entered one bit at time on rows of mechanical switches (plug boards). Programming languages were unknown (not even assembly languages). Operating systems were unheard of.

The 1950’s — Second Generation

By the early 1950’s, the routine had improved somewhat with the introduction of punch cards. The General Motors Research Laboratories implemented the first operating systems in early 1950’s for their IBM 701. The system of the 50’s generally ran one job at a time. These were called single-stream batch processing systems because programs and data were submitted in groups or batches.

The 1960’s - Third Generation

The systems of the 1960’s were also batch processing systems, but they were able to take better advantage of the computer’s resources by running several jobs at once. So operating systems designers developed the concept of multiprogramming in which several jobs are in main memory at once; a processor is switched from job to job as needed to keep several jobs advancing while keeping the peripheral devices in use.

For example, on the system with no multiprogramming, when the current job paused to wait for other I/O operation to complete, the CPU simply sat idle until the I/O finished. The solution for this problem that evolved was to partition memory into several pieces, with a different job in each partition. While one job was waiting for I/O to complete, another job could be using the CPU.

Another major feature in third-generation operating system was the technique called spooling (simultaneous peripheral operations on line). In spooling, a high-speed device like a disk interposed between a running program and a low-speed device involved with the program in input/output Instead of writing directly to a printer, for example, outputs are written to the disk. Programs can run to completion faster, and other programs can be initiated sooner when the printer becomes available, the outputs may be printed.

Another feature present in this generation was time-sharing technique, a variant of multiprogramming technique, in which each user has an on-line (i.e., directly connected) terminal. Because the user is present and interacting with the computer, the computer system must respond quickly to user requests, otherwise user productivity could suffer. Timesharing systems were developed to multiprogram large number of simultaneous interactive users.

II. Continue the following sentences.

1. The earliest electronic digital computers had...

2. By the early 1950’s, the routine had improved somewhat with the introduction of …

3. The systems of the 50’s were called single-stream batch processing systems because...

4. The systems of the 1960’s were able to take better advantage of the computer’s resources by... Operating systems designers developed the concept of multiprogramming in which...

5. Another major feature in third-generation operating system was the technique called...

6. Another feature present in this generation was...

7. Time-sharing technique is a variant of...