Read the text again and answer the questions with some of the words in bold.
Some say that a computer without an operating system is like a car without a driver. Others compare it to the human body without a brain. So what exactly is an operating system, or OS, and what does it do?
In a nutshell, an operating system is the most important software that enables a user to communicate with a computer using a keyboard and a mouse. Early computers lacked an operating system as we know it, and users had to rely on a command line interface to operate them. Nowadays, nearly all computers have Graphical User Interface (GUI) operating systems, which are a lot more intuitive and user-friendly than their predecessors.
The function of an operating system can be likened to the function of a headmaster of a school. The headmaster creates an environment in which teachers can work effectively by allocating available resources, i.e. providing classrooms for different classes, assigning classes to teachers, etc. Similarly, the function of an operating system is to manage the usage of all the hardware resources (CPU, memory, storage) effectively.
Microsoft Windows is the most popular operating system for personal computers. It is reputed to be easy to install, crash-free and have astounding graphics support. Apple Mac OS X, which comes preloaded on all Mackintosh computers, is the second most popular OS, followed by Linux, a free open-source operating system. Mobile devices, such as smartphones or tablets, are also run using operating systems, with Android and Apple iOS being the most prevailing choices.