froms on html

Click on one of the text labels to toggle the related control:

The cat was playing in the garden.

chapter 2-Homework Problems and Questions R2

What is the difference between network architecture and application architecture?

A network architecture is a layered service that works in more than one easily described process. While an application architecture is designed by the application developer and dictates how the application is structured over the various end system, a network architecture is designed as a complex system meant to implement many services. The best way to describe it is the five-layer internet protocol; application, transport, network, link, and physical

chapter 2-Homework Problems and Questions R1

List five nonproprietary Internet applications and the application-layer protocols that they use.
______________________________________________

The Web: HTTP;
file transfer: FTP;
remote login: Telnet;
 Network News: NNTP;
 e-mail:SMTP.

blender models

earth
explosion
particular
texture

in the link 

BLEDNDER S400 TRUCK AND PATRIOT MODELS

THE blender models are in the link.
*rockets are fired
*patriot truck is moving with rockets
*patriot radar are ready to detect
*s400 are ready to move and radar ready to detect.

INSTALLING PYTHON WITH LIBRARY ALL LIBRARYES

if you are searching how to install a library of python and there are so many libraries you need to install using python then you have to  just download and install the python.but before install the python make sure You removed Python from your Pc. Because when You dowload libraries it may be saved previous version of Python. In that time when You run your code It will still warn you that library is installed. 

there are too many libraries in python each time you need one you have to run cmd and type "pip install library_name"

then click enter. 

here we go:

firs make sure that you add python and script to the path.

later:

pip install sklearn

pip install pandas

Sometimes You run this code will have some error. "Excpected Error"

Once you have this error: restart your Computer and try pip install again. 

Blender Tire

I have prepared a tire using  blender. I want t share it with you.

feel free to use download. and if any erorr happen to download just write in comments. 

to download the tire model click here

To go to my channel go DEVELOP TO IMPROVE

Exercise Set One (Chapters 1/2/3)
Problem: Define the essential properties of the following types of operating systems:

         a. Batch b. Interactive c. Time sharing d. Real-Time e. Distributed
Answer:

1. Batch: Jobs with similar needs are batched together and run through the computer as a group by an operator or automatic job sequencer. Performance is increased by attempting to keep CPU and I/O devices busy at all times through buffering, off-line operation, spooling, and multiprogramming. Batch is good for executing large jobs that need little interaction; it can be submitted and picked up later.
2. Interactive: Composed of many short transactions where the results of the next transaction may be unpredictable. Response time needs to be short(seconds) since the user submits and waits for the result.
3. Time sharing: Uses CPU scheduling and multiprogramming to provide economical interactive use of a system. The CPU switches rapidly from one user to another. Instead of having jobs defined by spooled card images, each program reads its next control card from the terminal, and output is normally printed immediately to the screen.
4. Real-Time: A Real Time system must complete certain processes within a fixed time frame else the system will fail. Certain operations such as information retrieval with an unknown time to complete must be bounded by some known number in order to provide such guarantees. This often eliminates the option of using storage other than fast memory. In a soft real-time system, such deadlines are not guaranteed, but certain processes are given a priority over others with out any notion of a deadline to provide for faster completion.
5. Distributed Systems: These are systems which do not share common disks memory or clocks. Communication and collaboration is achieved through an inter-connected network. Distributed systems can be autonomous and act as an independent entity as in the case of Network operating systems or can appear as a small part of a much larger whole made up of many separate computers collaborating on the same task.

Problem: What are the differences between a trap and an interrupt? What is the use of each function?
Answer:

An interrupt is a hardware-generated change-of-flow within the system. An interrupt handler is summoned to deal with the cause of the interrupt; control is then returned to the interrupted context and instruction. A trap is a software-generated interrupt. An interrupt can be used to signal the completion of an I/O to obviate the need for device polling. A trap can be used to call operating system routines or to catch arithmetic errors.

Problem: Which of the following instructions should be privileged?

1. Set value of timer
2. Read the clock
3. Clear memory
4. Turn off interrupts
5. Switch form user to monitor mode

Answer:
The following instructions should be privileged

• Set value of timer
• Clear memory
• Turn off interrupts
• Switch form user to monitor mode

Problem: When are caches useful? What problems do they solve ? What problems do they cause? If a cache can be made as large as the device for which it is caching ( for instance, a cache as large as a disk), why not make it that large and eliminate the device?
Answer:

Caches are useful when two or more components need to exchange data, and the components perform transfers at differing speeds. Caches solve the transfer problem by providing a buffer of intermediate speed between the components. If the fast device finds the data it needs in the cache, it need not wait for the slower device. The data in the cache must be kept consistent  with the data in the components. If a component has a data value change, and the datum is also in the cache, the cache must also be updated. This is especially a problem on multiprocessor systems where more than one process may be accessing a datum. A component may be eliminated by an equal-sized cache, but only if :
1. the cache and the component have equivalent state-saving capacity ( that is, if the component retains its data when electricity is removed, the cache must retain data as well) , and
2. the cache is affordable, because faster storage tends to be more expensive.

Problem:      What are the five major activities of an operating system in regard to process management?
Answer:

1. The creation and deletion of both user and system processes.
2. The suspension and resumption of processes
3. The provision of mechanisms for process synchronization
4. The provision of mechanisms for process communication
5. The provision of mechanisms for deadlock handling

Problem:      What are the three major activities of an operating system in regard to memory management?
Answer:

1. Keep track of which parts of memory are currently being used and by whom
2. Decide which processes are to be loaded into memory when memory space becomes available
3. Allocate and deallocate memory space as needed

Problem:     List five services provided by an operating system. Explain how each provides convenience to the users. Explain also in which cases it would be impossible for user-level programs to provide these services.
Answer:

1. Program Execution: The operating system loads the contents (or sections) of a file into memory and begins its execution. A user-level program could not be trusted to properly allocate CPU time.
2. I/O operations: Disks, tapes, serial lines, and other devices must be communicated with a very low level. The user need only specify the device and the operation to perform on it, while the system converts that request into device or controller specific commands. User-level programs cannot be trusted to only access devices they should have access to, and to only access them when they are otherwise unused.
3. File-system manipulation: There are many details in file creation, deletion, allocation, and naming that users should not have to perform. Blocks of disk space are used by files and must be tracked. Deleting a file requires removing the name file information and freeing the allocated blocks. Protections must also be checked to assure proper file access. User programs could ensure neither adherence to protection methods nor could they be trusted to allocate only free blocks and deallocate blocks on file deletion.
4. Communications: Message passing between systems requires messages be turned into packets of information, sent to the network controller, transmitted across a communications medium, and reassembled by the destination system. Packet ordering and date correction must take place. Again, user programs might not coordinate access to the network device, or they may receive packets destined for other processes.
5. Error detection: Error detection occurs at both the hardware and software levels. At the hardware level, all data transfers must be inspected to ensure that data have not been corrupted in transit. All data on media must be checked to be sure they have not changed since they were written to the media. At the software level, media must be checked for data consistency; for instance, do the number of allocated and unallocated process- independent (for instance, the corruption of data on a disk), so there must be a global program(the operating system) that handles all types of errors. Also, by having errors processed by the operating system, processes need not contain code to catch and correct all the errors possible on a system.

Chapter 3
Problem 3.1: Describe the differences among short-term, medium-term, and long-term scheduling.
Answer:

• Short-term:(CPU scheduler)- selects from jobs in memory, those jobs which are ready to execute, and allocates the CPU to them.
• Medium-term - used especially with time-sharing systems as an intermediate scheduling level. A swapping scheme is implemented to remove partially run programs from memory and reinstate them later to continue where they left off.
• Long-term (job scheduler) - determines which jobs are brought into memory for processing.
The primary difference is in the frequency of their execution. The short-term must select a new process quite often. Long-term is used much less often since it handles placing jobs in the system, and may wait a while for a job to finish before it admits another one.

Problem 3.2: Describe the actions taken by a kernel to switch context

         a. Among threads  b. Among processes

Answer:

1. The thread context must be saved(registers and accounting if appropriate), and another thread's context must be loaded.
2. The same as (a), plus the memory context must be stored and that of the next process must be loaded.

Consider the “exactly once”semantic with respect to the RPC mechanism.
Does the algorithm for implementing this semantic execute correctly
even if the ACK message sent back to the client is lost due to a network
problem? Describe the sequence of messages, and discuss whether
“exactly once” is still preserved.



answer:https://youtu.be/Wo9jlaz8h0k

operationg system 3rd chapter

The Sun UltraSPARC processor has multiple register sets. Describe what happens when a context switch occurs if the new context is already loaded into one of the register sets. What happens if the new context is in memory rather than in a register set and all the register sets are in use? 


Answer: 

The CPU current-register-set pointer is changed to point to the set containing the new context, which takes very little time. If the context is in memory, one of the contexts in a register set must be chosen and be moved to memory, and the new context must be loaded from memory into the set. This process takes a little more time than on systems with one set of registers, depending on how a replacement victim is selected.

operation system chapter 3

3.3 Original versions of Apple's mobile iOS operating system provided no means of concurrent processing. Discuss three major complications that
concurrent processing adds to an operating system.

1. The OS has to keep track of the main memory address space allocated to each process so that a process does not affect or harm other processes data. This is a necessary , for example, a virus may try to destroy or modify other process data.
2. Switching from one process to another process leads to time overhead(时间开销), this requires storing the current register values and loading the register values of the next process from its PCB(program Control Block).
3. If a running process requires large space in memory then other process needs to be dumped back to hard disk which again leads to time overhead.

erorr on web pages 404 500 300

part of Hypertext Transfer Protocol -- HTTP/1.1

RFC 2616 Fielding, et al.

10.1 Informational 1xx

This class of status code indicates a provisional response, consisting only of the Status-Line and optional headers, and is terminated by an empty line. There are no required headers for this class of status code. Since HTTP/1.0 did not define any 1xx status codes, servers MUST NOT send a 1xx response to an HTTP/1.0 client except under experimental conditions.

A client MUST be prepared to accept one or more 1xx status responses prior to a regular response, even if the client does not expect a 100 (Continue) status message. Unexpected 1xx status responses MAY be ignored by a user agent.

Proxies MUST forward 1xx responses, unless the connection between the proxy and its client has been closed, or unless the proxy itself requested the generation of the 1xx response. (For example, if a

proxy adds a "Expect: 100-continue" field when it forwards a request, then it need not forward the corresponding 100 (Continue) response(s).)

10.1.1 100 Continue

The client SHOULD continue with its request. This interim response is used to inform the client that the initial part of the request has been received and has not yet been rejected by the server. The client SHOULD continue by sending the remainder of the request or, if the request has already been completed, ignore this response. The server MUST send a final response after the request has been completed. See section 8.2.3 for detailed discussion of the use and handling of this status code.

10.1.2 101 Switching Protocols

The server understands and is willing to comply with the client's request, via the Upgrade message header field (section 14.42), for a change in the application protocol being used on this connection. The server will switch protocols to those defined by the response's Upgrade header field immediately after the empty line which terminates the 101 response.

The protocol SHOULD be switched only when it is advantageous to do so. For example, switching to a newer version of HTTP is advantageous over older versions, and switching to a real-time, synchronous protocol might be advantageous when delivering resources that use such features.

10.2 Successful 2xx

This class of status code indicates that the client's request was successfully received, understood, and accepted.

10.2.1 200 OK

The request has succeeded. The information returned with the response is dependent on the method used in the request, for example:

GET an entity corresponding to the requested resource is sent in the response;

HEAD the entity-header fields corresponding to the requested resource are sent in the response without any message-body;

POST an entity describing or containing the result of the action;

TRACE an entity containing the request message as received by the end server.

10.2.2 201 Created

The request has been fulfilled and resulted in a new resource being created. The newly created resource can be referenced by the URI(s) returned in the entity of the response, with the most specific URI for the resource given by a Location header field. The response SHOULD include an entity containing a list of resource characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. The origin server MUST create the resource before returning the 201 status code. If the action cannot be carried out immediately, the server SHOULD respond with 202 (Accepted) response instead.

A 201 response MAY contain an ETag response header field indicating the current value of the entity tag for the requested variant just created, see section 14.19.

10.2.3 202 Accepted

The request has been accepted for processing, but the processing has not been completed. The request might or might not eventually be acted upon, as it might be disallowed when processing actually takes place. There is no facility for re-sending a status code from an asynchronous operation such as this.

The 202 response is intentionally non-committal. Its purpose is to allow a server to accept a request for some other process (perhaps a batch-oriented process that is only run once per day) without requiring that the user agent's connection to the server persist until the process is completed. The entity returned with this response SHOULD include an indication of the request's current status and either a pointer to a status monitor or some estimate of when the user can expect the request to be fulfilled.

10.2.4 203 Non-Authoritative Information

The returned metainformation in the entity-header is not the definitive set as available from the origin server, but is gathered from a local or a third-party copy. The set presented MAY be a subset or superset of the original version. For example, including local annotation information about the resource might result in a superset of the metainformation known by the origin server. Use of this response code is not required and is only appropriate when the response would otherwise be 200 (OK).

10.2.5 204 No Content

The server has fulfilled the request but does not need to return an entity-body, and might want to return updated metainformation. The response MAY include new or updated metainformation in the form of entity-headers, which if present SHOULD be associated with the requested variant.

If the client is a user agent, it SHOULD NOT change its document view from that which caused the request to be sent. This response is primarily intended to allow input for actions to take place without causing a change to the user agent's active document view, although any new or updated metainformation SHOULD be applied to the document currently in the user agent's active view.

The 204 response MUST NOT include a message-body, and thus is always terminated by the first empty line after the header fields.

10.2.6 205 Reset Content

The server has fulfilled the request and the user agent SHOULD reset the document view which caused the request to be sent. This response is primarily intended to allow input for actions to take place via user input, followed by a clearing of the form in which the input is given so that the user can easily initiate another input action. The response MUST NOT include an entity.

10.2.7 206 Partial Content

The server has fulfilled the partial GET request for the resource. The request MUST have included a Range header field (section 14.35) indicating the desired range, and MAY have included an If-Range header field (section 14.27) to make the request conditional.

The response MUST include the following header fields:

      - Either a Content-Range header field (section 14.16) indicating

        the range included with this response, or a multipart/byteranges

        Content-Type including Content-Range fields for each part. If a

        value MUST match the actual number of OCTETs transmitted in the

        Content-Length header field is present in the response, its

        message-body.

      - Date

      - ETag and/or Content-Location, if the header would have been sent

        in a 200 response to the same request

      - Expires, Cache-Control, and/or Vary, if the field-value might

        differ from that sent in any previous response for the same

        variant

If the 206 response is the result of an If-Range request that used a strong cache validator (see section 13.3.3), the response SHOULD NOT include other entity-headers. If the response is the result of an If-Range request that used a weak validator, the response MUST NOT include other entity-headers; this prevents inconsistencies between cached entity-bodies and updated headers. Otherwise, the response MUST include all of the entity-headers that would have been returned with a 200 (OK) response to the same request.

A cache MUST NOT combine a 206 response with other previously cached content if the ETag or Last-Modified headers do not match exactly, see 13.5.4.

A cache that does not support the Range and Content-Range headers MUST NOT cache 206 (Partial) responses.

10.3 Redirection 3xx

This class of status code indicates that further action needs to be taken by the user agent in order to fulfill the request. The action required MAY be carried out by the user agent without interaction with the user if and only if the method used in the second request is GET or HEAD. A client SHOULD detect infinite redirection loops, since such loops generate network traffic for each redirection.

      Note: previous versions of this specification recommended a

      maximum of five redirections. Content developers should be aware

      that there might be clients that implement such a fixed

      limitation.

10.3.1 300 Multiple Choices

The requested resource corresponds to any one of a set of representations, each with its own specific location, and agent- driven negotiation information (section 12) is being provided so that the user (or user agent) can select a preferred representation and redirect its request to that location.

Unless it was a HEAD request, the response SHOULD include an entity containing a list of resource characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content- Type header field. Depending upon the format and the capabilities of

the user agent, selection of the most appropriate choice MAY be performed automatically. However, this specification does not define any standard for such automatic selection.

If the server has a preferred choice of representation, it SHOULD include the specific URI for that representation in the Location field; user agents MAY use the Location field value for automatic redirection. This response is cacheable unless indicated otherwise.

10.3.2 301 Moved Permanently

The requested resource has been assigned a new permanent URI and any future references to this resource SHOULD use one of the returned URIs. Clients with link editing capabilities ought to automatically re-link references to the Request-URI to one or more of the new references returned by the server, where possible. This response is cacheable unless indicated otherwise.

The new permanent URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

If the 301 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

      Note: When automatically redirecting a POST request after

      receiving a 301 status code, some existing HTTP/1.0 user agents

      will erroneously change it into a GET request.

10.3.3 302 Found

The requested resource resides temporarily under a different URI. Since the redirection might be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires header field.

The temporary URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

If the 302 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

      Note: RFC 1945 and RFC 2068 specify that the client is not allowed

      to change the method on the redirected request.  However, most

      response, performing a GET on the Location field-value regardless

      existing user agent implementations treat 302 as if it were a 303

      been added for servers that wish to make unambiguously clear which

      of the original request method. The status codes 303 and 307 have

      kind of reaction is expected of the client.

10.3.4 303 See Other

The response to the request can be found under a different URI and SHOULD be retrieved using a GET method on that resource. This method exists primarily to allow the output of a POST-activated script to redirect the user agent to a selected resource. The new URI is not a substitute reference for the originally requested resource. The 303 response MUST NOT be cached, but the response to the second (redirected) request might be cacheable.

The different URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s).

      Note: Many pre-HTTP/1.1 user agents do not understand the 303

      status. When interoperability with such clients is a concern, the

      302 status code may be used instead, since most user agents react

      to a 302 response as described here for 303.

10.3.5 304 Not Modified

If the client has performed a conditional GET request and access is allowed, but the document has not been modified, the server SHOULD respond with this status code. The 304 response MUST NOT contain a message-body, and thus is always terminated by the first empty line after the header fields.

The response MUST include the following header fields:

      - Date, unless its omission is required by section 14.18.1

If a clockless origin server obeys these rules, and proxies and clients add their own Date to any response received without one (as already specified by [RFC 2068], section 14.19), caches will operate correctly.

      - ETag and/or Content-Location, if the header would have been sent

        in a 200 response to the same request

      - Expires, Cache-Control, and/or Vary, if the field-value might

        differ from that sent in any previous response for the same

        variant

If the conditional GET used a strong cache validator (see section 13.3.3), the response SHOULD NOT include other entity-headers. Otherwise (i.e., the conditional GET used a weak validator), the response MUST NOT include other entity-headers; this prevents inconsistencies between cached entity-bodies and updated headers.

If a 304 response indicates an entity not currently cached, then the cache MUST disregard the response and repeat the request without the conditional.

If a cache uses a received 304 response to update a cache entry, the cache MUST update the entry to reflect any new field values given in the response.

10.3.6 305 Use Proxy

The requested resource MUST be accessed through the proxy given by the Location field. The Location field gives the URI of the proxy. The recipient is expected to repeat this single request via the proxy. 305 responses MUST only be generated by origin servers.

      Note: RFC 2068 was not clear that 305 was intended to redirect a

      single request, and to be generated by origin servers only.  Not

      observing these limitations has significant security consequences.

10.3.7 306 (Unused)

The 306 status code was used in a previous version of the specification, is no longer used, and the code is reserved.

10.3.8 307 Temporary Redirect

The requested resource resides temporarily under a different URI. Since the redirection MAY be altered on occasion, the client SHOULD continue to use the Request-URI for future requests. This response is only cacheable if indicated by a Cache-Control or Expires header field.

The temporary URI SHOULD be given by the Location field in the response. Unless the request method was HEAD, the entity of the response SHOULD contain a short hypertext note with a hyperlink to the new URI(s) , since many pre-HTTP/1.1 user agents do not understand the 307 status. Therefore, the note SHOULD contain the information necessary for a user to repeat the original request on the new URI.

If the 307 status code is received in response to a request other than GET or HEAD, the user agent MUST NOT automatically redirect the request unless it can be confirmed by the user, since this might change the conditions under which the request was issued.

10.4 Client Error 4xx

The 4xx class of status code is intended for cases in which the client seems to have erred. Except when responding to a HEAD request, the server SHOULD include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. These status codes are applicable to any request method. User agents SHOULD display any included entity to the user.

If the client is sending data, a server implementation using TCP SHOULD be careful to ensure that the client acknowledges receipt of the packet(s) containing the response, before the server closes the input connection. If the client continues sending data to the server after the close, the server's TCP stack will send a reset packet to the client, which may erase the client's unacknowledged input buffers before they can be read and interpreted by the HTTP application.

10.4.1 400 Bad Request

The request could not be understood by the server due to malformed syntax. The client SHOULD NOT repeat the request without modifications.

10.4.2 401 Unauthorized

The request requires user authentication. The response MUST include a WWW-Authenticate header field (section 14.47) containing a challenge applicable to the requested resource. The client MAY repeat the request with a suitable Authorization header field (section 14.8). If the request already included Authorization credentials, then the 401 response indicates that authorization has been refused for those credentials. If the 401 response contains the same challenge as the prior response, and the user agent has already attempted authentication at least once, then the user SHOULD be presented the entity that was given in the response, since that entity might include relevant diagnostic information. HTTP access authentication is explained in "HTTP Authentication: Basic and Digest Access Authentication" [43].

10.4.3 402 Payment Required

This code is reserved for future use.

10.4.4 403 Forbidden

The server understood the request, but is refusing to fulfill it. Authorization will not help and the request SHOULD NOT be repeated. If the request method was not HEAD and the server wishes to make public why the request has not been fulfilled, it SHOULD describe the reason for the refusal in the entity. If the server does not wish to make this information available to the client, the status code 404 (Not Found) can be used instead.

10.4.5 404 Not Found

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent. The 410 (Gone) status code SHOULD be used if the server knows, through some internally configurable mechanism, that an old resource is permanently unavailable and has no forwarding address. This status code is commonly used when the server does not wish to reveal exactly why the request has been refused, or when no other response is applicable.

10.4.6 405 Method Not Allowed

The method specified in the Request-Line is not allowed for the resource identified by the Request-URI. The response MUST include an Allow header containing a list of valid methods for the requested resource.

10.4.7 406 Not Acceptable

The resource identified by the request is only capable of generating response entities which have content characteristics not acceptable according to the accept headers sent in the request.

Unless it was a HEAD request, the response SHOULD include an entity containing a list of available entity characteristics and location(s) from which the user or user agent can choose the one most appropriate. The entity format is specified by the media type given in the Content-Type header field. Depending upon the format and the capabilities of the user agent, selection of the most appropriate choice MAY be performed automatically. However, this specification does not define any standard for such automatic selection.

      Note: HTTP/1.1 servers are allowed to return responses which are

      not acceptable according to the accept headers sent in the

      406 response. User agents are encouraged to inspect the headers of

      request. In some cases, this may even be preferable to sending a

      an incoming response to determine if it is acceptable.

If the response could be unacceptable, a user agent SHOULD temporarily stop receipt of more data and query the user for a decision on further actions.

10.4.8 407 Proxy Authentication Required

This code is similar to 401 (Unauthorized), but indicates that the client must first authenticate itself with the proxy. The proxy MUST return a Proxy-Authenticate header field (section 14.33) containing a challenge applicable to the proxy for the requested resource. The client MAY repeat the request with a suitable Proxy-Authorization header field (section 14.34). HTTP access authentication is explained in "HTTP Authentication: Basic and Digest Access Authentication" [43].

10.4.9 408 Request Timeout

The client did not produce a request within the time that the server was prepared to wait. The client MAY repeat the request without modifications at any later time.

10.4.10 409 Conflict

The request could not be completed due to a conflict with the current state of the resource. This code is only allowed in situations where it is expected that the user might be able to resolve the conflict and resubmit the request. The response body SHOULD include enough

information for the user to recognize the source of the conflict. Ideally, the response entity would include enough information for the user or user agent to fix the problem; however, that might not be possible and is not required.

Conflicts are most likely to occur in response to a PUT request. For example, if versioning were being used and the entity being PUT included changes to a resource which conflict with those made by an earlier (third-party) request, the server might use the 409 response to indicate that it can't complete the request. In this case, the response entity would likely contain a list of the differences between the two versions in a format defined by the response Content-Type.

10.4.11 410 Gone

The requested resource is no longer available at the server and no forwarding address is known. This condition is expected to be considered permanent. Clients with link editing capabilities SHOULD delete references to the Request-URI after user approval. If the server does not know, or has no facility to determine, whether or not the condition is permanent, the status code 404 (Not Found) SHOULD be used instead. This response is cacheable unless indicated otherwise.

The 410 response is primarily intended to assist the task of web maintenance by notifying the recipient that the resource is intentionally unavailable and that the server owners desire that remote links to that resource be removed. Such an event is common for limited-time, promotional services and for resources belonging to individuals no longer working at the server's site. It is not necessary to mark all permanently unavailable resources as "gone" or to keep the mark for any length of time -- that is left to the discretion of the server owner.

10.4.12 411 Length Required

The server refuses to accept the request without a defined Content- Length. The client MAY repeat the request if it adds a valid Content-Length header field containing the length of the message-body in the request message.

10.4.13 412 Precondition Failed

The precondition given in one or more of the request-header fields evaluated to false when it was tested on the server. This response code allows the client to place preconditions on the current resource metainformation (header field data) and thus prevent the requested method from being applied to a resource other than the one intended.

10.4.14 413 Request Entity Too Large

The server is refusing to process a request because the request entity is larger than the server is willing or able to process. The server MAY close the connection to prevent the client from continuing the request.

If the condition is temporary, the server SHOULD include a Retry- After header field to indicate that it is temporary and after what time the client MAY try again.

10.4.15 414 Request-URI Too Long

The server is refusing to service the request because the Request-URI is longer than the server is willing to interpret. This rare condition is only likely to occur when a client has improperly converted a POST request to a GET request with long query information, when the client has descended into a URI "black hole" of redirection (e.g., a redirected URI prefix that points to a suffix of itself), or when the server is under attack by a client attempting to exploit security holes present in some servers using fixed-length buffers for reading or manipulating the Request-URI.

10.4.16 415 Unsupported Media Type

The server is refusing to service the request because the entity of the request is in a format not supported by the requested resource for the requested method.

10.4.17 416 Requested Range Not Satisfiable

A server SHOULD return a response with this status code if a request included a Range request-header field (section 14.35), and none of the range-specifier values in this field overlap the current extent of the selected resource, and the request did not include an If-Range request-header field. (For byte-ranges, this means that the first- byte-pos of all of the byte-range-spec values were greater than the current length of the selected resource.)

When this status code is returned for a byte-range request, the response SHOULD include a Content-Range entity-header field specifying the current length of the selected resource (see section 14.16). This response MUST NOT use the multipart/byteranges content- type.

10.4.18 417 Expectation Failed

The expectation given in an Expect request-header field (see section 14.20) could not be met by this server, or, if the server is a proxy, the server has unambiguous evidence that the request could not be met by the next-hop server.

10.5 Server Error 5xx

Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has erred or is incapable of performing the request. Except when responding to a HEAD request, the server SHOULD include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. User agents SHOULD display any included entity to the user. These response codes are applicable to any request method.

10.5.1 500 Internal Server Error

The server encountered an unexpected condition which prevented it from fulfilling the request.

10.5.2 501 Not Implemented

The server does not support the functionality required to fulfill the request. This is the appropriate response when the server does not recognize the request method and is not capable of supporting it for any resource.

10.5.3 502 Bad Gateway

The server, while acting as a gateway or proxy, received an invalid response from the upstream server it accessed in attempting to fulfill the request.

10.5.4 503 Service Unavailable

The server is currently unable to handle the request due to a temporary overloading or maintenance of the server. The implication is that this is a temporary condition which will be alleviated after some delay. If known, the length of the delay MAY be indicated in a Retry-After header. If no Retry-After is given, the client SHOULD handle the response as it would for a 500 response.

      Note: The existence of the 503 status code does not imply that a

      server must use it when becoming overloaded. Some servers may wish

      to simply refuse the connection.

10.5.5 504 Gateway Timeout

The server, while acting as a gateway or proxy, did not receive a timely response from the upstream server specified by the URI (e.g. HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed to access in attempting to complete the request.

      Note: Note to implementors: some deployed proxies are known to

      return 400 or 500 when DNS lookups time out.

10.5.6 505 HTTP Version Not Supported

The server does not support, or refuses to support, the HTTP protocol version that was used in the request message. The server is indicating that it is unable or unwilling to complete the request using the same major version as the client, as described in section 3.1, other than with this error message. The response SHOULD contain an entity describing why that version is not supported and what other protocols are supported by that server.

explicit and implicit programming languages

Explicit done by programmer. Everything need to be done by the programmer. Think about int x=4 in C programing. C is explicit which mean programmer need to define type of variable. But in python we dont need to dine as int x=5. Because pythom is implicit pramming language. 

static scope

#include <stdio.h>
#include <stdlib.h>

int main()
{
     int x=1;
     int y=1;
    if(y==1){
        int x=2;
    }
    printf("%d",x);
}


when I run the code it prints 1 on the screen. anyone has any idea?

What is the difference between an intrinsic attribute and a nonintrinsic synthesized attribute?

16. What is the difference between an intrinsic attribute and a nonintrinsic synthesized attribute?

            An intrinsic attribute is an inherent characteristic of a terminal symbol in the grammar (e.g., an identifier in a program). So the value of the attribute is determined solely from the terminal symbol. A nonintrinsic synthesized attribute is an attribute of a non-terminal symbol in the grammar. It’s value depends on the values of the attributes in the children of that non-terminal symbol’s nod in the parse tree.

How to Access Wikipedia if it is Banned.

let's say u will search Computer_programming

https://en.wikipedia.org › wiki › Computer_programming

that is what u got. but it cant access. then just put 0(zero)

before W as below.

https://en.0wikipedia.org › wiki › Computer_programmingTthen Then here we go it is accessed now.

https://en.0wikipedia.org › wiki › Computer_programming

http://pelajaranbahasaprogram.blogspot.com/2014/09/chapter-1-concepts-of-programming.html

1. Do you believe our capacity for abstract thought is influenced by our
language skills? Support your opinion.

Answer: Yes I do believe our capacity for abstract thought is defenitely influenced by our language skills because our abstract thought is one of important reason we can make programs. There are a number of programming domains that have radically different requirements, such as scientific and business, that dismiss any notion of a simple language for all programming domains as well as the different language evaluation criteria.

2. What are some features of specific programming languages you know
whose rationales are a mystery to you?

Answer: Basically, I have made some websites of my own using HTML as the interface. But then there was appeared a new born of HTML, it's called HTML5. It makes me curious becasue I've seen lot of HTML5 based sites can use kind of flash animation or video but those are not. For the example, let's take a look at this site Super Looper (Click Here), that site provides us kind of DJ Drum Pads application which we can play and use like we are using flash, but as a matter of fact it's just a normal interface site. So it's still kind of mystery to me.

3. What arguments can you make for the idea of a single language for all
programming domains?

Answer: It's a brilliant idea. Imagine when we have just one single language for all programming domains, everytime programmers make a project that involves programmers from particular programming domains, programmers would do much better teamwork because they can fully understand each other and the result would make the project to become much better.

4. What arguments can you make against the idea of a single language for
all programming domains?

Answer: Every programmers are supposed to master particular programming domains of their own. Because when programmers are making a project that involves particular programming domains, they would need teamwork. Teamwork means that programmers will try to cooperate, using their individual skills and providing constructive feedback, despite any personal conflict between individuals. If there were a single language for all programming domains, then it would not necessary to have a teamwork of programmers.

5. Name and explain another criterion by which languages can be judged
(in addition to those discussed in this chapter).

Answer: There's another criterion of languages in addition to those discussed in this chapter. One possibility is Straightforward. In some languages, a great deal of text is required for even simple complete programs. For example, COBOL is very rambling. Programs written in COBOL tend to be much longer than the same programs written in other languages. To be Straightforward on the languages, it can improves program creation, takes less file space for the source programs, and can cause programs to be more readability.

https://adhywiranatabinusian.wordpress.com/2013/03/04/concept-of-programming-languages-chapter-1-review-questions/



1. Why is it useful for a programmer to have some background in language design, even though he or she may never actually design a programming language?

By understanding the basic of language design, programmer can fully understood the concepts of the programming, so they can implement the concept to many other programming languages, since those concepts are used in common, such as control structures, error/exception handling, array/memory management. The basics are the most important part to establish something. This is also applicable in the programming development. Different languages, similar concept. It’s really useful for a programmer to be able to adapt to many programming languages.

2. How can knowledge of programming language characteristics benefit the whole computing community?

By knowing the characteristics of programming languages, it would make the learning of a new language is easier and get more people involved in a programming. Easier learning process and involving more people would resulted many new programming languages which are easier to understand and run things better.

3. What programming language has dominated scientific computing over the past 50 years?

Fotran (Formula Translator)

4. What programming language has dominated business applications over the past 50 years?

COBOL (Common Business-Oriented Language)

5. What programming language has dominated artificial intelligence overthe past 50 years?

LISP

6. In what language is most of UNIX written?

C, because it is relatively easy to port or move to different machines.

7. What is the disadvantage of having too many features in a language?

-When the features are not well-designed, it would be quite confusing to use
-The programmer don’t have a clue of how the features should be used or what is the purpose of the features
-Similar features with different names but works with similar purposes.
-Some of the features may be out of scope for the language, as this will increase memory requirements, and thin out performance efforts.

8. How can user-defined operator overloading harm the readability of a program?

User-defined operator can overloading harm the readability of a program because the built in operator has the precision and compiler knows all the precision between the operators, and it works on that precision. User can also create its own operator but the compiler does not come to know how to make precision of this operator. This will be the cause of the overloading harm.

9. What is one example of a lack of orthogonality in the design of C?

C language is inconsistent in its treatment of concepts and language structure,leading some exceptions to the rules of the language, for example, although C has two kinds of structured daya types which are arrays and structs, structs can be returned from functions but arrays not. A member of a structure can be any data type except void or a structure of the same type. An array element can be any data type except void or a function.

10. What language used orthogonality as a primary design criterion?

ALGOL 68

11.What primitive control statement is used to build more complicated control statements in languages that lack them?

The selection statement plus GOTO is used to build more complicated control statements such as FOR loop.

12. What construct of a programming language provides process abstraction?

subprogram which used to implement a sort algorithm that is required several times in a program.

13. What does it mean for a program to be reliable?

A program is said to be reliable if it performs to its specifications under all conditions.

14. Why is type checking the parameters of a subprogram important?

Type checking is an important factor in language reliability because it’s testing for type errors in a given program, either by the compiler or during the execution of a program. Type checking
the parameters of a subprogram would be necessary because a failure may lead to countless program errors.

15. What is aliasing?

Aliasing means having two or more distinct names that can be used to access the same memory cell.

16. What is exception handling?

Exception halding is the ability of a program to intercept run-time errors and other unusual conditions detectable by the program and take corrective measures then continue which is an obvious aid to reliability.

17. Why is readability important to writability?

Readability is important to writability because programs that are difficult to read will be difficult to be written or modified.

18. How is the cost of compilers for a given language related to the design of that language?

The cost of compilers for a given language is related to the design of it because a languange that requires many run-time type checks will prohibit fast code execution, regardless of the quality of the compiler.

19. What has been the strongest influences on programming language design over the past 50 years?

Von Neumann architecture

20. What is the name of the category of programming languages whose structure is dictated by the
von Neumann computer achitecture?

Imperative Language

21. What two programming language deficiencies were discovered as a result of the researh in software development in the 1970s?

Two programming language deficiencies were discovered as a result of the research in software development in the 1970s were called top-down design and stepwise refinement   
 Incompleteness of type checking and inadequacy of control statements (GOTO statements)  

22. What are the three fundamental features of an object oriented programming language?

Encapsulation, Inheritance, and Polymorphism

23. What language was the first to support the three fundamental features of object-oriented programming?

Smalltalk

24. What is the example of two language design criteria that are in direct conflict with each other?

Reliability and cost of execution

25. What are three general methods of implementing a programming language?

Compilation, Pure Interpretation, Hybrid Implementation.

26. Which produces faster program execution, a compiler or a pure interpreter?

Compiler

27. What role does the symbol table play in a compiler?

The compiler converts each user –defined line into a machine readable code then back to user readable language. The symbol table shows the process and how the user-defined code in translated to lexical and syntax analysis then is generated to semantics analysis and code generation. The Symbol table basically shows the load module, linking, and loading process.

28. What is the utility of byte code?

Byte code provides portability to any machine that has a byte code interpreter and an asspcoated run-time system.

29. What is a hybrid implementation system?

Hybrid implementation system is an implementation of a method which translate high-level language programs to an intermediate
language designed to allow easy interpretation.

30. What are the advantages of using Borland JBuilder?
Borland JBuilder provides an integrated compiler, editor, debugger, and file system for Java development,
where all four are accessed through a graphical interface.