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Trapdoor is a secret undocumented entry point into a program USED to grant ACCESS without normal methods of access authentication. A trap is a SOFTWARE interrupt, usually the result of an ERROR condition.

Trapdoor is a secret undocumented entry point into a program used to grant access without normal methods of access authentication. A trap is a software interrupt, usually the result of an error condition.

In message PASSING, it is the CONDITION in which, both, the SENDER and RECEIVER are blocked until the message is delivered.

In message passing, it is the condition in which, both, the sender and receiver are blocked until the message is delivered.

We encounter CYCLE stealing in the context of Direct Memory Access (DMA). Either the DMA CONTROLLER can use the data bus when the CPU does not need it, or it may force the CPU to temporarily SUSPEND operation. The latter technique is called cycle stealing. Note that cycle stealing can be done only at specific break points in an instruction cycle.

We encounter cycle stealing in the context of Direct Memory Access (DMA). Either the DMA controller can use the data bus when the CPU does not need it, or it may force the CPU to temporarily suspend operation. The latter technique is called cycle stealing. Note that cycle stealing can be done only at specific break points in an instruction cycle.

The set of dispatchable processes is in a SAFE STATE if there EXISTS at least one temporal order in which all processes can be run to COMPLETION without resulting in a DEADLOCK.

The set of dispatchable processes is in a safe state if there exists at least one temporal order in which all processes can be run to completion without resulting in a deadlock.

Resident set is that portion of the process image that is ACTUALLY in real-memory at a particular instant. Working set is that subset of resident set that is actually needed for execution. (Relate this to the variable-window SIZE method for SWAPPING TECHNIQUES.)

Resident set is that portion of the process image that is actually in real-memory at a particular instant. Working set is that subset of resident set that is actually needed for execution. (Relate this to the variable-window size method for swapping techniques.)

In a cached system, the base ADDRESSES of the last few referenced pages is MAINTAINED in registers called the TLB that aids in faster lookup. TLB contains those page-table entries that have been most recently used. Normally, each virtual memory reference causes 2 PHYSICAL memory accesses- one to fetch appropriate page-table entry, and one to fetch the DESIRED data. Using TLB in-between, this is REDUCED to just one physical memory access in cases of TLB-hit.

In a cached system, the base addresses of the last few referenced pages is maintained in registers called the TLB that aids in faster lookup. TLB contains those page-table entries that have been most recently used. Normally, each virtual memory reference causes 2 physical memory accesses- one to fetch appropriate page-table entry, and one to fetch the desired data. Using TLB in-between, this is reduced to just one physical memory access in cases of TLB-hit.

User data: Modifiable part of user space. May include program data, user stack area, and programs that may be modified.

User program: The instructions to be executed.

SYSTEM Stack: Each process has one or more LIFO STACKS associated with it. Used to store parameters and calling addresses for PROCEDURE and system calls.

Process control Block (PCB): Info NEEDED by the OS to control PROCESSES.

User data: Modifiable part of user space. May include program data, user stack area, and programs that may be modified.

User program: The instructions to be executed.

System Stack: Each process has one or more LIFO stacks associated with it. Used to store parameters and calling addresses for procedure and system calls.

Process control Block (PCB): Info needed by the OS to control processes.

TURNAROUND time is the interval between the SUBMISSION of a job and its COMPLETION. RESPONSE time is the interval between submission of a request, and the first response to that request.

Turnaround time is the interval between the submission of a job and its completion. Response time is the interval between submission of a request, and the first response to that request.

To ACCESS TERMINAL , you have to go under Application MENU -> ACCESSORIES -> Terminal .

To access terminal , you have to go under Application Menu -> Accessories -> Terminal .

To RESET the unity configuration the simplest way to do is to hit open a TERMINAL or hit Atl-F2 and RUN the COMMAND # unity –reset.

To reset the unity configuration the simplest way to do is to hit open a Terminal or hit Atl-F2 and run the command # unity –reset.

Export is a command in Bash shell LANGUAGE, when you try to set a VARIABLE, it is visible or exported to any subprocess STARTED from that instance of bash. The variable will not EXIST in the sub-process WITHOUT the export command.

Export is a command in Bash shell language, when you try to set a variable, it is visible or exported to any subprocess started from that instance of bash. The variable will not exist in the sub-process without the export command.

There is no CONCEPT of Folder in Ubuntu. Everything INCLUDING your HARDWARE is a FILE.

There is no concept of Folder in Ubuntu. Everything including your hardware is a FILE.

The filename would appear as EXAMPL~1.TXT . The REASON BEHIND this is that FILENAMES under this operating system is limited to 8 characters when WORKING under DOS environment.

The filename would appear as EXAMPL~1.TXT . The reason behind this is that filenames under this operating system is limited to 8 characters when working under DOS environment.

• Internal commands are built-in commands that are already PART of the operating system. 
• EXTERNAL commands are separate file PROGRAMS that are stored in a separate folder or DIRECTORY.

NOS is short for NETWORK OPERATING System. It is a specialized software that will allow a COMPUTER to communicate with other devices over the network, including file/folder sharing.

NOS is short for Network Operating System. It is a specialized software that will allow a computer to communicate with other devices over the network, including file/folder sharing.

It is the PROCESS of using the output of one program as an INPUT to another. For example, instead of sending the listing of a folder or drive to the main screen, it can be piped and sent to a file, or sent to the PRINTER to PRODUCE a hard copy.

It is the process of using the output of one program as an input to another. For example, instead of sending the listing of a folder or drive to the main screen, it can be piped and sent to a file, or sent to the printer to produce a hard copy.

Partitioning and formatting CREATES a PREPARATORY environment on the drive so that the operating system can be copied and installed properly. This includes ALLOCATING space on the drive, designating a drive name, DETERMINING and creating the APPROPRIATE file system structure.

Partitioning and formatting creates a preparatory environment on the drive so that the operating system can be copied and installed properly. This includes allocating space on the drive, designating a drive name, determining and creating the appropriate file system structure.

Preemptive multitasking allows an operating system to SWITCH between software programs. This in turn allows MULTIPLE programs to RUN WITHOUT necessarily taking complete control over the processor and resulting in system crashes.

Preemptive multitasking allows an operating system to switch between software programs. This in turn allows multiple programs to run without necessarily taking complete control over the processor and resulting in system crashes.

GUI is short for GRAPHICAL User Interface. It provides users with an interface wherein actions can be performed by interacting with icons and graphical symbols. People find it EASIER to interact with the COMPUTER when in a GUI especially when using the mouse. Instead of having to remember and type commands, users just click on buttons to PERFORM a process.

GUI is short for Graphical User Interface. It provides users with an interface wherein actions can be performed by interacting with icons and graphical symbols. People find it easier to interact with the computer when in a GUI especially when using the mouse. Instead of having to remember and type commands, users just click on buttons to perform a process.

Interrupts are part of a hardware mechanism that sends a notification to the CPU when it wants to gain access to a particular resource. An INTERRUPT handler RECEIVES this interrupt signal and “TELLS” the processor to TAKE action based on the interrupt REQUEST.

Interrupts are part of a hardware mechanism that sends a notification to the CPU when it wants to gain access to a particular resource. An interrupt handler receives this interrupt signal and “tells” the processor to take action based on the interrupt request.

An assembler acts as a translator for low level language. Assembly CODES, written USING MNEMONIC commands are translated by the Assembler into machine language.

An assembler acts as a translator for low level language. Assembly codes, written using mnemonic commands are translated by the Assembler into machine language.

Spooling is normally associated with PRINTING. When different applications WANT to send an OUTPUT to the printer at the same time, spooling takes all of these print jobs into a disk FILE and queues them accordingly to the printer.

Spooling is normally associated with printing. When different applications want to send an output to the printer at the same time, spooling takes all of these print jobs into a disk file and queues them accordingly to the printer.

Caching is the processing of utilizing a region of FAST memory for a limited data and PROCESS. A cache memory is usually MUCH efficient because of its HIGH access speed.

Caching is the processing of utilizing a region of fast memory for a limited data and process. A cache memory is usually much efficient because of its high access speed.

A command line interface allows the user to TYPE in commands that can IMMEDIATELY provide results. Many SEASONED computer users are well accustomed to using the command line because they FIND it quicker and simpler. The main problem with a command line interface is that users have to be familiar with the commands, including the switches and parameters that come with it. This is a downside for people who are not fond of memorizing commands.

A command line interface allows the user to type in commands that can immediately provide results. Many seasoned computer users are well accustomed to using the command line because they find it quicker and simpler. The main problem with a command line interface is that users have to be familiar with the commands, including the switches and parameters that come with it. This is a downside for people who are not fond of memorizing commands.

I/O STATUS information provides info about which I/O DEVICES are to be ALLOCATED for a particular process. It also shows which files are opened, and other I/O DEVICE state.

I/O status information provides info about which I/O devices are to be allocated for a particular process. It also shows which files are opened, and other I/O device state.

• Accumulators
• INDEX Registers
• STACK POINTER
• GENERAL Purpose Registers

VFS, or VIRTUAL File System, SEPARATES file system generic OPERATIONS from their implementation by defining a clean VFS interface. It is also based on a file-representation structure known as vnode, which CONTAINS a NUMERICAL designator needed to support network file systems.

VFS, or Virtual File System, separates file system generic operations from their implementation by defining a clean VFS interface. It is also based on a file-representation structure known as vnode, which contains a numerical designator needed to support network file systems.

Device DRIVERS provides a standard means of representing I/O devices that MAYBE MANUFACTURED by different companies. This prevents CONFLICTS WHENEVER such devices are incorporated in a systems unit.

Device drivers provides a standard means of representing I/O devices that maybe manufactured by different companies. This prevents conflicts whenever such devices are incorporated in a systems unit.

Root partition is where the operating system KERNEL is located. It also CONTAINS other POTENTIALLY important system files that are MOUNTED during boot time.

Root partition is where the operating system kernel is located. It also contains other potentially important system files that are mounted during boot time.

Typically, the different attributes for a file STRUCTURE are naming, identifier, supported file TYPES, and LOCATION for the files, size, and LEVEL of protection.

Typically, the different attributes for a file structure are naming, identifier, supported file types, and location for the files, size, and level of protection.

The BEST PAGING size varies from SYSTEM to system, so there is no single best when it comes to page size. There are different factors to consider in order to COME up with a suitable page size, such as page table, paging time, and its effect on the overall efficiency of the OPERATING system.

The best paging size varies from system to system, so there is no single best when it comes to page size. There are different factors to consider in order to come up with a suitable page size, such as page table, paging time, and its effect on the overall efficiency of the operating system.

THRASHING refers to an instance of HIGH PAGING activity. This happens when it is spending more time paging instead of executing.

Thrashing refers to an instance of high paging activity. This happens when it is spending more time paging instead of executing.

DIRECT Access method is based on a disk model of a file, such that it is viewed as a numbered SEQUENCE of blocks or records. It allows arbitrary blocks to be READ or written. Direct access is advantageous when ACCESSING large amounts of INFORMATION.

Direct Access method is based on a disk model of a file, such that it is viewed as a numbered sequence of blocks or records. It allows arbitrary blocks to be read or written. Direct access is advantageous when accessing large amounts of information.

NEW State – MEANS a PROCESS is being created

Running – means instructions are being EXECUTED

Waiting – means a process is waiting for CERTAIN conditions or events to occur

Ready – means a process is waiting for an instruction from the main processor

Terminate – means a process is done executing

New State – means a process is being created

Running – means instructions are being executed

Waiting – means a process is waiting for certain conditions or events to occur

Ready – means a process is waiting for an instruction from the main processor

Terminate – means a process is done executing

During regular intervals that are SET by the operating system, processes can be copied from main MEMORY to a backing store, and then copied BACK LATER. Swapping allows more processes to be RUN that can fit into memory at one time.

During regular intervals that are set by the operating system, processes can be copied from main memory to a backing store, and then copied back later. Swapping allows more processes to be run that can fit into memory at one time.

Fragmentation is memory wasted. It can be INTERNAL if we are dealing with systems that have fixed-sized ALLOCATION units, or EXTERNAL if we are dealing with systems that have variable-sized allocation units.

Fragmentation is memory wasted. It can be internal if we are dealing with systems that have fixed-sized allocation units, or external if we are dealing with systems that have variable-sized allocation units.

Paging is a memory MANAGEMENT scheme that PERMITS the physical-address space of a process to be NONCONTIGUOUS. It AVOIDS the considerable problem of having to fit varied sized memory chunks ONTO the backing store.

Paging is a memory management scheme that permits the physical-address space of a process to be noncontiguous. It avoids the considerable problem of having to fit varied sized memory chunks onto the backing store.

Overlays are used to enable a PROCESS to be LARGER than the amount of memory allocated to it. The basic IDEA of this is that only INSTRUCTIONS and data that are needed at any given time are kept in memory.

Overlays are used to enable a process to be larger than the amount of memory allocated to it. The basic idea of this is that only instructions and data that are needed at any given time are kept in memory.

With dynamic loading, a routine is not LOADED until it is called. This method is especially useful when large AMOUNTS of CODE are NEEDED in order to handle infrequently occurring cases such as error ROUTINES.

With dynamic loading, a routine is not loaded until it is called. This method is especially useful when large amounts of code are needed in order to handle infrequently occurring cases such as error routines.

LOGICAL address REFERS to the address that is generated by the CPU. On the other hand, physical address refers to the address that is seen by the MEMORY UNIT.

Logical address refers to the address that is generated by the CPU. On the other hand, physical address refers to the address that is seen by the memory unit.

One is that it depends on how often a deadlock is LIKELY to OCCUR under the implementation of this ALGORITHM. The other has to do with how MANY PROCESSES will be affected by deadlock when this algorithm is applied.

One is that it depends on how often a deadlock is likely to occur under the implementation of this algorithm. The other has to do with how many processes will be affected by deadlock when this algorithm is applied.

1. RAID 0 – Non-redundant striping
2. RAID 1 – MIRRORED DISKS
3. RAID 2 – Memory-style error-correcting codes
4. RAID 3 – Bit-interleaved PARITY
5. RAID 4 – Block-interleaved Parity
6. RAID 5 – Block-interleaved distributed Parity
7. RAID 6 – P+Q REDUNDANCY

Deadlock SITUATIONS occur when four conditions occur simultaneously in a SYSTEM: Mutual EXCLUSION; Hold and WAIT; No preemption; and Circular wait.

Deadlock situations occur when four conditions occur simultaneously in a system: Mutual exclusion; Hold and Wait; No preemption; and Circular wait.

RR (round-robin) scheduling algorithm is primarily aimed for time-sharing SYSTEMS. A CIRCULAR QUEUE is setup in such a way that the CPU scheduler goes around that queue, allocating CPU to each process for a time interval of up to around 10 to 100 milliseconds.

RR (round-robin) scheduling algorithm is primarily aimed for time-sharing systems. A circular queue is setup in such a way that the CPU scheduler goes around that queue, allocating CPU to each process for a time interval of up to around 10 to 100 milliseconds.

FCFS is short for First-come, first-served, and is one TYPE of scheduling ALGORITHM. In this scheme, the process that requests the CPU first is ALLOCATED the CPU first. IMPLEMENTATION is managed by a FIFO queue.

FCFS is short for First-come, first-served, and is one type of scheduling algorithm. In this scheme, the process that requests the CPU first is allocated the CPU first. Implementation is managed by a FIFO queue.

• there is an increased RESPONSIVENESS to the user
• resource SHARING within the process
• economy
• UTILIZATION of multiprocessing architecture

In asymmetric clustering, a machine is in a state KNOWN as hot standby MODE where it does nothing but to monitor the ACTIVE server. That machine takes the active server’s role should the server fails.

In asymmetric clustering, a machine is in a state known as hot standby mode where it does nothing but to monitor the active server. That machine takes the active server’s role should the server fails.

Server systems can be CLASSIFIED as either computer-server systems or FILE server systems. In the first case, an interface is made available for clients to SEND requests to PERFORM an action. In the second case, provisions are available for clients to create, access and update files.

Server systems can be classified as either computer-server systems or file server systems. In the first case, an interface is made available for clients to send requests to perform an action. In the second case, provisions are available for clients to create, access and update files.

SMP is short for SYMMETRIC MULTIPROCESSING, and is the most COMMON type of multiple-processor SYSTEMS. In this system, each processor runs an identical copy of the operating system, and these copies communicate with one another as NEEDED.

SMP is short for Symmetric MultiProcessing, and is the most common type of multiple-processor systems. In this system, each processor runs an identical copy of the operating system, and these copies communicate with one another as needed.

In a Time sharing system, the CPU executes multiple jobs by switching among them, ALSO known as MULTITASKING. This PROCESS happens so fast that USERS can actually interact with each program while it is running.

In a Time sharing system, the CPU executes multiple jobs by switching among them, also known as multitasking. This process happens so fast that users can actually interact with each program while it is running.