OS Introduction

Operating System

An Operating System can be defined as an interface between user and hardware. It is responsible for the execution of all the processes, Resource Allocation, CPU management, File Management and many other tasks. The purpose of an operating system is to provide an environment in which a user can execute programs in a convenient and efficient manner.

Types of Operating Systems

Operating systems are categorized based on their processing capabilities:

• Batch OS – A set of similar jobs are stored in the main memory for execution. A job gets assigned to the CPU, only when the execution of the previous job completes.
• Multiprogramming OS – The main memory consists of jobs waiting for CPU time. The OS selects one of the processes and assigns it to the CPU. Whenever the executing process needs to wait for any other operation (like I/O), the OS selects another process from the job queue and assigns it to the CPU. This way, the CPU is never kept idle.
• Multitasking OS – Multitasking OS combines the benefits of Multiprogramming OS and CPU scheduling to perform quick switches between jobs. The switch is so quick that the user can interact with each program as it runs.
• Time Sharing OS – Time-sharing systems require interaction with the user to instruct the OS to perform various tasks. The OS responds with an output. The instructions are usually given through an input device like the keyboard.
• Real Time OS – Real-Time OS are usually built for dedicated systems to accomplish a specific set of tasks within deadlines.