Operating System

This week we learned operating system and its main functions.

To understand operating system, it is useful for us to recognize its position within the hierarchy of software. It belongs to system software and has its counterpart application software.

Operating system serves as the intermediary between the computer hardware and application software, so that it provides the hardware resources needed to run the application software. It serves many functions, including providing GUI, memory management, peripheral management, disk management.

Memory Management

This function of operating system makes sure each application has the necessary space, both memory on disk and on RAM, to perform tasks. It allocates specific location of the disk and RAM to be used by the software.

Resource management

OS also manages CPU resources to be used by different software, achieving multi-tasking.  Different tasks will receive its time slot and be processed, and tasks will be coordinated according to their priority.

In fact, the recent two computer viruses utilize the bug within the resource management system. Different softwares have different access clearance. The meltdown attack allows a program to access the memory, and thus also the secrets, of other programs and the operating system. THe Spcetre attack breaks the isolation between different applications. It allows an attacker to trick error-free programs into leaking their secrets.

affected products, given by Intel.

Interface

There are mainly four types of user interface: Graphical User Interface, Comand line interface, menu-based interface, and natural language interface.

GUI is the most common one in the modern era. It allows user to interact with graphics. CLI has a high level of precision yet does not allow multitasking and is highly professional, this can still be seen in Windows or Mac’s terminal. Menu-based interface works well on simply systems, yet does not give users much option, and this is common in BIOS. For natural language interface, it is the new fancy, and Siri is one example. Its disadvantage is obvious; it is too ambiguous.

an example of command line interface on mac os. 

an example of natural language interface: siri on MacBook.

Storage

There are four types of permanent storage and they each have their advantages and disadvantages.

Fix head magnetic disk storage: The circles on the disk are called tracks. It has fixed read and write heads.

Movable head magnetic disk (hard disk): It has 1 read-write head. Advantages: more space for data, reduced cost; Disadvantages: constrained by the speed of the moving head.

Optical disk storage: It moves at constant angular velocity. It uses laser to access the data. Blue-ray disks can store data in thinner layers, thus increasing storage.

Flash memory: It is electrical erasable programmable (EEP) read-only memory.