Introduction
Every computer you touch — a bank server, an ATM, your smartphone, the PC at a government office — runs an operating system (OS). The OS is the master program that sits between the raw hardware (CPU, memory, disk, devices) and the application programs (browser, MS Word, a banking app). Without it, every application would have to know how to control the hardware directly, which is impossible in practice.
For BCS, Bank IT-officer and other government IT recruitment exams, "Operating System Overview and Types" is one of the highest-yield topics. Examiners love questions such as "Which of the following is system software?", "What is time-sharing?", "Real-time OS is used in ___?", and "Which OS handles multiple users simultaneously?". This lesson builds the topic from first principles so that no MCQ or short-answer question can surprise you.
Learning Objectives
After studying this lesson you will be able to:
- Define an operating system and explain why it is needed.
- List and explain the major functions of an OS (process, memory, file, device, security management).
- Distinguish system software from application software.
- Classify operating systems into their standard types (batch, multiprogramming, multitasking, time-sharing, multiprocessing, distributed, network, real-time, embedded, mobile) and give real examples of each.
- Explain the difference between kernel and shell, and between hard and soft real-time systems.
- Solve numerical questions on CPU utilization, time-sharing quantum and throughput.
- Avoid the common traps set in competitive exams.