Q.7 Write Short Notes on (ANY TWO)
a) Linear Layout Vs Relative Layout
b) Embedded Linux
c) 802.11 Ans.a) Linear Layout Vs Relative LayoutLinearLayout arranges all child control in vertically or horizontally. You can provide the layout direction with the android:orientation attribute. In this layout all the controls are placed in single row or single column. By default the layout orientation is horizontal. You can change it as vertical by using the following code:
android:orientation="vertical"
Some of the important attribute of
< LinearLayout > are as follows:
RelativeLayoutIn this layout child views (Controls) are positioned relative to each other. For example if you have placed a TextView control in this layout then you can place another control to the left, right or below the TextView.
Some of the important attribute of
< RelativeLayout > are as follows:
b) Embedded LinuxLinux is an operating system just like other operating system but it more secure than other. It that manages all of the hardware resources and other software associated with your system (Desktop, Laptop, and other devices). Linus is one of the most reliable computer system now a days and it is an open source.
The Linux kernel is written in the C programming language, and it supports nearly all major computer architectures.
Embedded Linux enables you to customize it according to the size and hardware constraints of embedded devices. Embedded Linux are usually compiled on one platform but executed on another.
The following are the main component of OS:
The Bootloader: It is a small application that is executed when you start the computer.
The kernel: The Linux kernel is the heart of any Linux Operating System. It provides the core services such as memory management, process and thread creation, scheduling, data exchange with hardware and peripheral devices.
Daemons: These are the program that runs in the background. These services runs either starts up during boot or after you log into the system.
The Shell: It is a program that takes your command and provides it to Linux OS to perform. Previously it was the only user interface available on a Unix OS but nowadays, it provides graphical user interfaces (GUIs) for this purpose.
Graphical Server: It that displays the graphics on your monitor.
Applications: Linux offers n numbers of high-quality software that can be easily found and installed. Lots of App Store-like tools are included in modern Linux distributions that centralize and simplify application installation. For example you can use Ubuntu Software Center which allows you to quickly search the apps and install them.
c) 802.11IEEE has developed specification for a wireless LAN and known as IEEE 802.11
A wireless LAN (WLAN ) is a transmission system that uses radio waves rather than a cable infrastructure for communication between computing devices.
Advantages for WLAN- Increased mobility.
- Cost-effective network setup.
- Real-time access.
- Access the LAN during movement.
IEEE defines two kinds of services:- Basic service set (BSS)
- Extended service set (ESS)
802.11 LANs use the BSS as the standard building block. A basic service set is made of mobile devices and an optional central base station, known as the access point (AP).An Access Point (AP) is works as bridge between Wireless and Wired Network. A BSS without an Access Point is called as ad hoc architecture. The BSS without an AP cannot send data to other BSSs.
Ad hoc network (BSS without an AP)
Extended Service SetAn extended service set (ESS) is created by using two or more BSSs with APs. BSSs are connected through a distribution system that is called as wired LAN.
Communication between two devices in two different BSSs usually occurs through the two access points.
