A451 Databases

A Database is a structured set of data held in a computer, especially one that is accessible in various ways.

What is a Db?
Give example of a serial file Db
Give example of a sequential Db
Talk about 3 levels of a Db view
The external view
The conceptual view
The physical view
What is a Flat file Db?
What is a hierarchical Db?

The data in the picture could be what the database is used for and what it stores.
A database records strings of information on what to do when data is input and decides where to put it and stores it to the file showing information attached.
You gain information for the collected data.
If a phone company had to take the customers name, number, address, and email the database will record it so next time when the customer calls back you can just look through the database and find their personal file of information and you can record even more information against their file and adding notes of their bills and what they have bought as their service.
Sequence databases can be searched using a variety of methods. The most common usage is probably searching for sequences similar to a certain target protein or gene whose sequence is already known to the user. A flat file database describes any of various means to encode a database model (most commonly a table) as a single file. A hierarchical database is a management system that links records together so that each record has only one owner. It represents information in a one to many relationship, e.g. parent may have more than one child but each child can only have one parent. They were used widely in the first mainframes but can not be used often as they do not relate to the structures in the real world.

Network Topology

Star topology goes across the line and then chooses the direction to where to go to send the information
A star topology involves using a central device, such as a switch, as the connection point for all systems. The advantage of a star topology is that a break in the line affects only the system connected to that cable.

 

Bus topology slows down when heavy traffic and there is lots of data collisions.
A bus topology consists of a main cable (known as a trunk) that all systems connect to. There are terminators at each end designed to absorb the electrical signal off the network. If there were no terminators, the signal would bounce back and collide with other data on the cable. One of the disadvantages of a bus topology is that if there is a break in the trunk, the entire network fails.

 

In a ring topology, hosts are connected to each other forming a large circle. In a single-ring topology, all of the device on the network share a single cable. The disadvantages of a single-ring topology are that data only travels in one direction, and if there is a break in the ring, the entire network will go down. In a dual-ring topology, there are 2-rings made from separate cables. This allows data to be sent in both directions and introduces fault tolerance as there would need to be a break in both lines to cause the network to go down.

Chapter 6 Network

LAN: (Local area network)

Advantages:
If your network is behind a good Firewall then it makes attacks much more difficult
A LAN allows more than one device to share information between each other like in a office if you had 5 computers and one printer all of the computer would be able to print to the same printer.

Disadvantages:
Every time you add a new device you'll need to add more wires
For only wireless devices like phones you wont be able to access the internet with it

NIC:

NIC is also known as a Network interface controller
The controller implements the electronics to communicate with each other

HUB:



                                                                                                                                       

Chapter 3 Software

3 Main categories of software:
Systems software
-Operating system
-Device drivers
-Firmware
-Servers
-Utilities
-Interfaces
Development software
(Programming languages and utilities)
-Applications

An operating system,  sometimes called a platform, is a collection of programs that control the hardware in a computer or device.
At the heart of the operating system is the Kernel which looks after the most low-level hardware operations.
-Multi-tasking allows the computer to make best use of the CPU.
The CPU works much faster than RAM and the other components of the computer.
White the CPU waits for the other actions to complete, e.g. loading data to RAM, it works on other tasks.
-Running: The CPU is currently dealing with this process and others must wait.
-Runnable: These are ready to go and just need the running program to finish or be interrupted to get the CPU's attention so they can run.
-Waiting: These processes are waiting to get into the queue and become runnable.
User interface
The user interface is how the user interacts with the system.
This can be provided as part of the operating system or ban be a separate program running on top of the operating system.
-Windows:  A powerful multi- tasking operating system from Microsoft. It provides a graphical user interface (GUI) that enables all applications running under windows to look similar.

Compilers  translate the high-level code used by the programmer into the machine instructions required by the computer.
Interpreters translate the high level code into code but they translate the code one line at a time.
Assemblers are used to translate assembly language programs into machine instructions.
Linkers are used to connect together sub programs to create larger programs.
Applications are programs that do real world jobs.
There is huge amount of apps to do lots of jobs on different devices.

1. Explain how an IDLE can help a programmer when producing source code [2 marks]
An IDLE can help a programmer by pointing out errors and showing if they have not closed their coding or any Syntax errors.

2. Little Johnny is a systems manager of a large insurance company.
He is choosing general purpose office software for the staff to use.
He is considering installing open source software.
(a) State what is meant by open source software [2 marks]
Open source software's source codes are free for anyone to use and improve and make any toggles with the software. They could improve it and give out the source code for others to use and make their own toggles with the open software and could claim it as theirs like the MAC Operating system which was made by a open source software (Linux)
(b)