Computing revison flash cards

Pregunta	Respuesta
Kernel Explaination	Manages system resources and maintains the communication between the hardware and software.
Five Types of Operating Systems	Multi-User, Real-Time, Multi-Tasking, Distributed, Embedded
Virtual Memory Explanation	Virtual memory is used when the RAM of your computer is filled, Virtual memory is temporary usage of hard drive data for RAM and is incredibly slow
All 3 Sorting Algorithms	Bubble Sort, Insertion Sort & Quick Sort
Two Types of Data Structure	Static & Dynamic
Differences between the two data structures	Memory is allocated to the data dynamically in a dynamic structure whereas data is fixed and unchangeable at compile time with a static structure
3 Operations in a stack	Pop, Push, Top
The functions of the 3 individual stack operations	Push - Adds an item to the top of the stack Pop - Removes an item from the top of the stack Top - Identifies the item at the top of the stack
Important parts of a stack	First in stack, Last in stack, Stack pointer
Logic Gate: Both inputs A & B	AND Gate
Logic Gate: Either inputs A or B (Both still means ON)	OR Gate
Logic Gate: No inputs	NOT Gate
Logic Gate: A or B but not both are true	XOR Gate
Logic Gate: Both A&B are false or true	XNOR Gate
De Morgan's Law	¬ (AVB) = ¬A ^ ¬B
Distributive Law	A (BVC) =ABVAC
Simplify: A V B V AC V AB	A V AC V AB V B (all a’s on one side) A (1 V C V B) V B (use distributive law to factor out A) A (1) V B (or anything by 1 returns 1) A V B (AND anything by 1 returns itself) Answer: A V B
Simplify: ¬AB V (A V B)	¬AB V A V B (remove brackets) B V ¬AB V A (commutative law to rearrange) B (1 V ¬A) V A (factor out B) B (1) V A (OR anything by 1 returns) B V A (AND anything by 1 returns itself) Answer: B V A
What is a Karnaugh Map?	A condensed map like a truth table, used to work out inputs & outputs of Boolean algorithms
Difference between lossless and lossy compression?	Lossy compression is irreversible,
What is a scheduler?	A program that manages the amount of time different processes have in the CPU
The Round Robin Scheduling Algorithm	Any open program is given an exact time to execute (quantum), the round robin consistently in a circle gives every other process the elapsed time to execute what it needs. Disadvantages in the way that it does not work in priorities.
First Come First Served Scheduling Algorithm	A basic method where any new process is given execute time immediately until it is fully open Can be much slower, but processes are always completed in their entirety.
Shortest Job First Scheduling Algorithm	A basic method where any process with a lower ‘wait time’ than the last is treated before others, this minimizes wait time.
Shortest Time Remaining Scheduling Algorithm	Slight difference to the SJB method where instead this method executes any job closest to completion.
Multi-level Feedback Queues Scheduling Algorithm	Multiple queues are made for the CPU to process and in each queue the instructions have different characteristics so the process are executed faster.
What is polling?	Polling is when the CPU keeps checking each peripheral/device to see if it needs attention.
What is a interrupt service routine?	At the end of each Fetch-decode-execute cycle, the processors check to see if there are any interrupts If there are, and are a higher priority than the current task the following steps are carried out. The contents of the program counter and other registers are copied to an area of memory called a stack The relevant ISR can be loaded by changing the program counter to the value where the ISR starts in memory When the ISR is complete, the previous values of the programs counter and other registers can be restored from the memory in the CPU
What is a device driver?	OS are expected to communicate with a wide variety of drivers, each with different models and manufactures. It would be impossible for makers of OS’s to program them to handle all existing and future devices, and this is why we have device drivers.
What is a virtual machine?	A fully operational operating system which runs as a program instead of from the BIOS.
The BIOS	Basic Input/output System When a computer first boots up it looks to the BIOS to get it up and running. The BIOS checks if the computer is briefly functional, memory installed and accessible and the processor is working. This is called the Power-On self-test.
Open and closed source software	Closed source is when the program (.exe) can be used but the actual source code is hidden from the user. Usually so that the code cannot be copied or stolen. Open source software has its own source code visible and openly editable for changes and using. The code and company is usually copyrighted so it cannot be used again as the same code.
Octal Arithmetic	Octal arithmetic is a lot like binary, except it works in powers of 8, meaning instead of a binary graph going 1,2,4,8,16... it would go 1,8,64,512...
What is a database?	A stored collection of information arranged in a logical, structured manner.
What is a record?	All of the data or information about one person or one thing.
What is a flat file?	All of your data is stored in one large table.
Pros and Cons of a flat file?	Pros: • All records are stored in one place • Easy to set up using a number of standard office applications • Easy to understand • Simple sorting of records can be carried out • Record can be viewed or extracted on the basis of simple criteria Cons: • Potential duplication. As more and more records are added to the database it becomes difficult to avoid duplicate records. This is because there is no mechanism built in to the system to prevent duplication. Later you will see how ‘primary keys’ are used to prevent this. • Non- unique records. Notice that Mr & Mrs Jones have identical ID’s This is because the person producing the database decided they may want to sort on identical telephone numbers and so has applied identical ID to the two records. This is fine for that purpose, but suppose you only wanted to extract Mrs Jones record. Now it is much more difficult • Harder to update. Suppose that this flat file database also stored • Inherently Inefficient. Consider a situation where the database now needs to hold an extra field to hold their email address. If there are tens of
Relational Database	Holds data over a number of tables instead of one. Records within the tables are linked (related) to records held in other tables.
3 Types of database keys	Primary Key, Secondary Key and Foreign Key
Primary Key	Identify the numbered record (A unique record) Primary keys do not have to be numbers, they can be anything that makes each record unique
Secondary Key	Indexes the records according to title Secondary keys can take up a lot of space in a database
Foreign Key	Points to a record in another table whose primary key is the same value.
What is an entity?	An Entity is a person, place, thing or concept about which data can be collected. Examples include EMPLOYEE, HOUSE, and CAR.
One to one relationships	Relationships between two singular pieces of data For example: Husband & Wife
One to many relationships	Relationships between a plural piece of data and a singular piece of data. For example: DiNitride and his content
Many to many relationships	Relationships between two plural pieces of data For example: A School's Students and their pencils (These are very very rare since they are so messy)
What is circuit switching in a network? An example?	A physical pathway is established between sender and receiver for the duration of the data transfer. The public telephone system is a good example of a switched network using circuit switched paths.
What is packet switching in a network? An example?	The message transmitted is split into packets and these are routed through intermediary nodes (connectors). A modern day PC & Router connection to the internet uses this type of switching
Pro and con of circuit switching?	Pro: All packets will arrive in the correct order. Con: Any break in the connection at all will fail the entire task.
Pro and con of packet switching?	Pro: Connection is resilient to failed links Cons: Packets don't arrive in order. This requires extra processing instead.
What is the internet?	A collection of inter-connected networks
What is the difference between the internet and the world wide web?	The World Wide Web is the theoretical way of referencing the internet, as the internet is more the physical make-up of the connections.
What does WAN & LAN stand for?	Wide-Area-Connection & Local-Area-Connection
What is a DNS and what does it do?	A Domain-Name-System translates website addresses into IPv4 addresses so that the device being used to access the website can connect by address.
What is an NIC and what does it do?	A Network-Interface-card can be wired or wireless and acts as a connection to your router.
What is a MAC address and what does it do?	A Media-Access-Control address is a important unique address that is assigned to every different device with a connection of some sort to another device. It is used to tell apart two different devices while processing.
Name all the parts of a TCP/IP stack (along with the layers)	Application layer: HTTP, FTP, HTTPS, Gopher Transport layer: TCP, UDP Internet layer: IP
What does HTML stand for and what is it?	Hyper-Text-Markup-Language is a coding language specifically designed to be efficient in developing websites.
What does SAP stand for and what is it?	A Service-Access-Point is the point in which protocols will communicate with each other.
During networking, what is 'Handshaking'?	In order to set up a communication link both devices need to agree on a set of protocols to use. This must occur before a single byte of data is sent and is known as hand shaking The handshaking signal is sent from one device to the other and is acknowledged by the second device.
JavaScript is a scripting language, what is a scripting language?	An interpreted programming language that is designed to work within some run-time environments, rather than generating object code that can be run directly from the OS. (Only understandable by certain devices)
Google sorts the website links on it's search engine by page rank, what is page rank?	Basically, to ranks pages according to its external links. If a page has a lot of links to it, then it is deemed more popular and therefor more significant. They also look at the importance of the websites that links to the website, as that can also increase the ranking. There are other issues like the dampening factor (probability of the user giving up clicking or continuing – generally around 0.85).

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