In DNS terms what is the purpose of an "A" record?

In DNS terms what is the purpose of an "A" record?

• Resolves the MAC address of a host from its name
• Resolves the IP address of a host from its name
• Resolves the IP address of a host from the MAC address
• Resolves the Host name from its MAC address 

 

EXPLANATION

https://support.dnsimple.com/articles/a-record/
An A record maps a domain name to the IP address (IPv4) of the computer hosting the domain. Simply put, an A record is used to find the IP address of a computer connected to the internet from a name.

SOURCE

https://support.dnsimple.com/articles/a-record/

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All email services are based on which software model?

All email services are based on which software model?

• SMTP
• Client/server
• POP3
• TCP 

 

EXPLANATION

The client–server model of computing is a distributed application structure that partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. A server host runs one or more server programs which share their resources with clients. A client does not share any of its resources, but requests a server's content or service function. Clients therefore initiate communication sessions with servers which await incoming requests.
Examples of computer applications that use the client–server model are email, network printing, and the web.

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What happens when a volatile variable is declared in Java programming?

What happens when a volatile variable is declared in Java programming?

• All reads and writes go straight to main memory
• It holds a lock
• It behaves as if enclosed in an asynchronous block
• The value of the variable will be cached locally 

 

EXPLANATION

The Java volatile variable is an example of a special mechanism to guarantee that communication happens between threads. Basically, the value of the variable can be modified by different threads. When you declare a volatile variable, the value of this variable will never be cached thread-locally. Instead, all reads and writes will go straight to main memory. Access to the variable acts as though it is enclosed in a synchronized block, synchronized on itself.
Access to a volatile variable never has the potential to block because you can only ever do a simple read or write, so unlike a synchronized block it never holds on to any lock. Because of this, volatile variables are not suited for cases where you want to use read-update-write as an atomic operation, unless you are willing to miss an update. 

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CRUD is create, read, update and delete. How can we interpret in sql commands?

CRUD is create, read, update and delete. How can we interpret in sql commands?

• Create, Read, Upgrade and Delete;
• Create, Read, Update and Delete;
• Insert, Select, Upgrade and Delet;
• Insert, Select, Update and Delete; 

 

EXPLANATION

This procedure performed using SQL is known as CRUD - Create, Read, Update and Delete which is nothing more than the composition of the basic operations that an application performs in a database, creating, reading, updating and deleting data. See the abbreviation CRUD mapped below:

Create -> INSERT;

Read -> SELECT;

Update -> UPDATE;

Delete -> DELETE.

SOURCE

https://www.sqlshack.com/creating-using-crud-stored-procedures/

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What is the term for a rogue access point that serves as a man in the middle from which further attacks can be carried out?

What is the term for a rogue access point that serves as a man in the middle from which further attacks can be carried out?

• War driving
• Twin driving
• War twinning
• Evil twin 

EXPLANATION

An evil twin is a rogue access point used for malicious purposes. The attacker acts as a man in the middle.

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In the early days of computer technology, what type of memory had to be hand made rather than by machine?

In the early days of computer technology, what type of memory had to be hand made rather than by machine?

• Thin film memory
• EPROM
• Magnetic core memory
• Bubble Memory 

 

EXPLANATION

Magnetic core memory was almost always "woven" by hand in spite of repeated attempts to automate the process. Core uses tiny magnetic beads (the cores), through which wires are threaded to write and read information.

SOURCE

https://en.wikipedia.org/wiki/Magnetic-core_memory

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Which is the standard file extension used by VMWare for virtual hard drive images?

Which is the standard file extension used by VMWare for virtual hard drive images?

• VHD (Virtual Hard Disk)
• VDI (Virtual Disk Image)
• VMDK (Virtual Machine Disk)
• HDD (Hard Disk Drive) 

 

EXPLANATION

VMDK is the standard used by VMWare and is supported by several other virtual hypervisors.  It can contain the entire virtual machine, including settings.
VHD is the standard typically used by Microsoft Hyper-V.  It represents a single virtual drive, and does not contain configuration settings for the rest of the virtual machine.
HDD is the standard for Parallels.
VDI is the standard and default for type-2 hypervisor VirtualBox; it can use and create all four of the listed formats, however.

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