# data[].attributes.attachment_link.readable_text
The fundamentals of the go language are given below:

Go tokens:

Tokens are the smallest individual units in the program. There are various tokens available in the go language; a few of them are given below:

1. Keywords: Keywords are pre-defined segments in the go language. These are the reserved words, which are stored in the library of GoLang.

2. Identifier: An identifier is a name that the developer in the program gives. It can be a variable name or function name or any user-defined functions in the go program.

3. Variable: A variable is just a name given to a particular memory space in the storage, by which the Go program manipulates that variable.

4. Constant: Constants are the fixed values in the program; they can't be changed during the execution process. These fixed values are also known as literals in the program.

5. String: A string is a combination of two or more two characters. These characters can be a symbol, or a name, or any numbers. A string is always enclosed with a pair of double quotes or a pair of back ticks.

6. Special character: Special characters are those who have special meaning in the go program.

7. Symbols: Symbols are those, which represent specific things in the program. For example, &, *, and many more.

We will take a deep look at these topics one by one also in the next chapter.

Whitespace:

Whitespace is the blank space in the program. This blank space can be tabs, newline characters, or comments in the go program. Space between two lines is also considered as whitespace.

A whole line can be considered whitespace only on one condition, i.e., when it contains the line comments. It is also known as a blank line. The compiler ignores this line during the compilation process.

Whitespaces also use to distinguish one part of the statement from another part in the program that helps the compiler identify the elements in a go program statement.
Example:
var num1 int;

var num2 int;

sum = num1 + num2;

Here; in the above example,

In the first two lines, it is mandatory to give whitespace between the keyword and variable name. This space distinguishes the keywords and variable names and helps the compiler in identifying them.

But in the last statement, the whitespace is optional. The developer gives the whitespace just for providing the readability in the program.

Line separator:

Line separator points out the end of a single logical statement. Line separator is not required in the go language. Any statement or line of code in the go program does not require any special character to describe statement terminator like C language. The line is separated by a semi-colon (;) in the C language. While in the go language, the compiler put the semi-colon internally during the compilation.

Data Type:

Data type tells the type of the data to the compiler at the time of the go program's execution. With the help of data type, the compiler decides how much memory will assign to the variable.

# data[].attributes.attachment_link.title
Fundamentals of Go Language - Tutorial And Example

# data[].attributes.attachment_link.description
The fundamentals of the go language are given below: Tokens are the smallest individual units in the program. There are various tokens available in the go language; a few of them are given below: Keywords: Keywords are pre-defined segments in the go language. These are the reserved words, which are stored in the library of GoLang.

# data[].attributes.attachment_link.description
C++ Deque with tutorial and examples on HTML, CSS, JavaScript, XHTML, Java, .Net, PHP, C, C++, Python, JSP, Spring, Bootstrap, jQuery, Interview Questions et...

# data[].attributes.attachment_link.readable_text
Files are used in Cobol to store data in the form of a disk or tape. Files are divided into records. Further, each record is divided into fields, .and lastly, these fields contain information about the data.
COBOL SUPPORTS THREE TYPES OF DATA FILES SEQUENTIAL FILE -

Also known as a flat-file

Store records in a sequential manner, i.e., one after another, stacked.

No access to the Nth record. You have to read the N-1th before proceeding to the Nth.

New records are added to the end, i.e., first come, first serve

These files have either fixed or variable length.

If there is a simple read and write function and very little search of the record is required, these files are recommended.

A line sequential file is a special type of sequential file where a carriage return separates each record ( X" 0D") or line feed ( X "0A") at the end of the last non-space character; these always contain variable-length records. These are also known as text files; to write a report file, the file should be define as a line sequential file.

INDEXED FILE -

These files can be accessed much faster, and the access is done using key values

They use alphanumeric characters as the key

These records can be accessed in any order irrespective of position using the key

Access mode can be sequential as well as random

In the index file, these key must be uniquely defined

In these files, the organization is always indexed

To write an indexed file, we must write the records in increasing order of the keys.

EXAMPLE =>

To write the record with key S007, we must write all the records with key less than S007,

KEYS are case sensitive, i.e., S007 is not the same as s007

The key field can not be updated in the indexed file.

We can delete a particular record in an indexed file, but the record can not be deleted physically, but the particular memory location can not be accessed for the record.
RELATIVE ORGANIZATION FILE -

Also known as relative record data set - RRDS - file

The record in these files can be accessed by - RRN - relative record number

It contains both random and sequential access

The record can be accessed in any order by declaring a 'RECORD KEY.'

In these files, the key should be a numeric constant

For example, we have to read a record with a specific key value, which we already knew, then, in this case, it's always best to define the files as RRDS.
VARIOUS OPTIONS INVOLVE IN FILE HANDLING FD CLAUSE -
FD refers to the file description. all the layout and description of the file needed to be declared here, and it becomes mandatory to be declared in FILE - SECTION under FD clause

SYNTAX =>

NOTE: -

F- FIXED, if the file contains fixed-length records.

V- VARIABLE, if the file contains a variable-length record.

U- UNDEFINED, if the file contains undefined length records (example - lode module)

[ RECORD CONTAINS N characters ] - Describes the size of the data record

FORMAT A)

RECORD CONTAINS 80 CHARACTERS ( fixed-length files )

FORMAT B)

RECORD CONTAINS SIZE N-1 TO N-2 CHARACTERS ( variable length)

FORMAT C)

RECORD IS VARYING IN SIZE N-1 TO N-2 [ DEPEND ON DATA-ITEM-NAME ]

{ dynamic files )
[ DATA RECORD IS RECORD - DET ] -
Record data name has been provided by them. Here RECORD-DET contains the layout of the file
[ BLOCK CONTAINS I RECORDS ] -
the block size of the file is defined through this. Used to determine the size of the physical record

FORMAT A)

RECORD CONTAINS 80 CHARACTERS ( fixed-length files )

FORMAT B)

RECORD CONTAINS SIZE N-1 TO N-2 CHARACTERS ( variable length)

FORMAT C)

RECORD IS VARYING IN SIZE N-1 TO N-2 [ DEPEND ON DATA-ITEM-NAME ]

{ dynamic files )

Special BLOCK CONTAINS 0 CHARACTERS for sequential (QSAM ) files.

While using this, we got the advantage to define the size of the block at run time
LOGICS OF FILE OPERATIONS
The logic of file operations is defined as followed.

To work in a file, we have to open the file first ( OPEN ), then we can perform our desired functionality READ / WRITE / REWRITE / DELETE functionality.

Later, we have to close the opened file in the end ( CLOSE ). After executing a program successfully, all the files are closed automatically, but it is way better to close the file manually to avoid further problems.
OPEN OPERATIONS
It is mandatory for all the files to be opened in PROCEDURAL DIVISION before other operations can be performed.

SYNTAX =>

OPEN INPUT FILE-NAME. ( file opened for reading )

OPEN OUTPUT FILE-NAME ( for writing )

OPEN I - O FILE - NAME ( for reading, writing and rewriting )

OPEN EXTEND FILE - NAME ( opened for appending only for relative and indexed file )
READ OPERATIONS
It is mandatory for all the input files to be read in PROCEDURAL DIVISION before the records are used later.

Only one record can be read from a file, and to keep on reading from the file, we have to continuously read files till the end file is reached.

SYNTAX =>
START OPERATIONS
These operations are used to place the pointer on a specific location in INDEXED or RELATIVE ORGANIZATION.

To abotain this it becomes mandatory for the file to be opened in I - O mode or input mode.

Access mode can either be sequential or dynamic.

Start doesn't get any record; instead, it sets the pointer to a specific reading record.

SYNTAX =>

EXAMPLE =>

START IDX - FILENAME

KEY IS EQUAL TO key - 1

INVALID KEY DISPLAY 'INVALID KEY '

NOT INVALID KEY DISPLAY 'VALID KEY '

END - START
WRITE OPERATIONS
SYNATX =>

FROM = optional

BEFORE ADVANCING option = this option is used to print line for report before the advancement of next page.

AFTER ADVANCING option = this option is used to print line for report after the advancement of next page.
REWRITE OPERATIONS
Used to update the previous record in a file, but it is mandatory for the file to be opened in I - O mode.

SYNTAX =>
DELETE OPERATIONS
Delete a previously stored record in a file that is opened in I - O mode only for indexed and

relative files and this cannot take place in sequential mode

Example =>

If the file is opened in random access mode, then provided the record key to perform DELETE operations.

SYNTAX =>
CLOSE OPERATIONS
Closing a file explicitly.
SYNTAX => VARIOUS ACCESS MODES IN A FILE
SEQUENTIAL ACCESS - records are accessed in sequential order

RANDOM ACCESS - to access the value randomly, we should know the value of the key

DYNAMIC ACCESS - a combination of sequential and random access
DYNAMIC ACCESS EXAMPLE =>
Let us consider we have a record of customers where the monthly expenditure forms the record key.

Now we have to find the customer who spends between $200 and $500 per month and those who spend $900 and above per month

1. Retrieve the first record randomly ( with random retrieval record READ ) based on the KEY 200

2. Now we will sequentially read ( using READ NEXT ) until expenditure exceeds 500

3. Switch back to random read with the key of value 900

4. After this, switch back to sequential and read till the end of the file

# data[].attributes.attachment_link.title
File Handling in COBOL - Tutorial And Example

# data[].attributes.attachment_link.description
Files are used in Cobol to store data in the form of a disk or tape. Files are divided into records. Further, each record is divided into fields, .and lastly, these fields contain information about the data. COBOL SUPPORTS THREE TYPES OF DATA FILES SEQUENTIAL FILE - Also known as a flat-file Store records in a sequential manner, i.e., one after another, stacked.

# data[].attributes.attachment_link.readable_text
Sequential file handling in COBOL

Sequential file is also known as a flat-file.

It stores records in a sequential manner, i.e., one after another, stacked.

In this, we cannot directly access to the Nth record. For this, we have to read the records till N-1th before proceeding to the Nth record.

All the new records are added to the end, i.e., first come, first serve.

These files can have either fixed or variable length.

If there is a case of simple read and write a function and very little search of the record is required, these files are recommended.

SYNTAX =>

SELECT logical - fl ASSIGNED to physical - fl

ORGANIZATION IS SEQUENTIAL

SELECT logical - fl ASSIGNED to physical - fl

ORGANIZATION IS LINE SEQUENTIAL

These must be coded in the FILE - CONTROL SECTION under INPUT-OUTPUT SECTION, defined under ENVIRONMENTAL DIVISION.

SAMPLE PROGRAM -1

This is a demo program to learn and understand the concept of sequential file handling and how to assign values from a different subprogram.

IDENTIFICATION DIVISION.

PROGRAM-ID. SEQFILE.

ENVIRONMENT DIVISION.

INPUT-OUTPUT SECTION.

FILE-CONTROL.

*INPYUT FILE

SELECT INFL ASSIGN TO INFLDD

ORGANIZATION IS SEQUENTIAL

FILE STATUS FS-INFL.

DATA DIVISION.

FILE SECTION.

FD INFL.

01 INFL-REC.

05 STORE-ID PIC 9(05).

05 FILLER PIC X(01).

05 ITEM-ID PIC X(10).

05 FILLER PIC X(64).

WORKING-STORAGE SECTION.

01 FS-INFL PIC X(02) VALUE SPACES.

88 FS-INFL-OK VALUE '00'.

88 FS-INFL-EOF VALUE '10'.

01 COUNTERS.

05 READ-COUNT PIC 9(2).

05 WRITE-COUNT PIC 9(2).

PROCEDURE DIVISION.

MAIN-PARA.

PERFORM OPEN-PARA THRU OPEN-EXIT-PARA.

PERFORM PROCESS-PARA THRU PROCESS-EXIT-PARA.

PERFORM CLOSE-PARA THRU CLOSE-EXIT-PARA.

STOP RUN.

OPEN-PARA.

INITIALIZE FS-INFL READ-COUNT WRITE-COUNT.

OPEN INPUT INFL

IF FS-INFL-OK

CONTINUE

ELSE

DISPLAY "FILE OPEN FAILED: " FS-INFL

END-IF.

OPEN-EXIT-PARA.

EXIT.

PROCESS-PARA.

PERFORM UNTIL FS-INFL-EOF.

READ INFL

AT END

IF READ-COUNT < 1.

DISPLAY 'NO RECORDS PRESENT'

GO TO EXIT-PARA

END-IF

NOT AT END

PERFORM WRITE-PARA THRU WRITE-EXIT-PARA

END-READ

END-PERFORM.

PROCESS-EXIT-PARA.

EXIT.

WRITE-PARA.

ADD 1 TO READ-COUNT.

IF STORE-ID > 12346

DISPLAY 'STORE-ID: ' STORE-ID

DISPLAY 'ITEM-ID: ' ITEM-ID

END-IF.

WRITE-EXIT-PARA.

EXIT.

CLOSE-PARA.

CLOSE INFL.

CLOSE-EXIT-PARA.

EXIT.

EXIT-PARA.

EXIT PROGRAM.
THE OUTPUT WILL BE
STORE ID: 12347

ITEM ID: DETER12347

STORE ID: 12348

ITEM ID: JKLH67545

STORE ID: 12350

ITEM ID: KLJ443232

Here in this program, we have assigned a few variables with different values and later manipulated the output using different data file handling properties to clarify the different concepts related to CALLED / SUBPROGRAM AND MAIN / CALLING PROGRAM.
SAMPLE PROGRAM -2
This is a demo program to learn and understand the concept of sequential file handling and how to read data from input files.

IDENTIFICATION DIVISION.

PROGRAM-ID. SEQFILE.

ENVIRONMENT DIVISION.

INPUT-OUTPUT SECTION.

FILE-CONTROL.

SELECT INFL ASSIGN TO INFLDD

ORGANIZATION IS SEQUENTIAL

FILE STATUS FS-INFL.

SELECT OUTFL ASSIGN TO OUTFLDD

ORGANIZATION IS SEQUENTIAL

FILE STATUS FS-OUTFL.

DATA DIVISION.

FILE SECTION.

FD INFL.

01 INFL-REC.

05 STORE-ID PIC 9(05).

05 FILLER PIC X(01).

05 ITEM-ID PIC X(10).

05 FILLER PIC X(64).

FD OUTFL.

01 OUTFL-REC.

05 O-STORE-ID PIC 9(05).

05 DELIMIT PIC X(01).

05 O-ITEM-ID PIC X(10).

05 FILLER PIC X(64).

WORKING-STORAGE SECTION.

01 FS-INFL PIC X(02) VALUE SPACES.

88 FS-INFL-OK VALUE '00'.

88 FS-INFL-EOF VALUE '10'.

01 FS-OUTFL PIC X(02) VALUE SPACES.

88 FS-OUTFL-OK VALUE '00'.

88 FS-OUTFL-EOF VALUE '10'.

01 COUNTERS.

05 READ-COUNT PIC 9(2).

05 WRITE-COUNT PIC 9(2).

PROCEDURE DIVISION.

MAIN-PARA.

PERFORM OPEN-PARA THRU OPEN-EXIT-PARA.

PERFORM PROCESS-PARA THRU PROCESS-EXIT-PARA.

PERFORM CLOSE-PARA THRU CLOSE-EXIT-PARA.

STOP RUN.

OPEN-PARA.

INITIALIZE FS-INFL FS-OUTFL READ-COUNT WRITE-COUNT.

OPEN INPUT INFL

IF FS-INFL-OK

CONTINUE

ELSE

DISPLAY "FILE OPEN FAILED: " FS-INFL

GO TO EXIT-PARA

END-IF.

OPEN OUTPUT OUTFL

IF FS-OUTFL-OK

CONTINUE

ELSE

DISPLAY "OUTPUT FILE OPEN FAILED: " FS-OUTFL

GO TO EXIT-PARA

END-IF.

OPEN-EXIT-PARA.

EXIT.

PROCESS-PARA.

PERFORM UNTIL FS-INFL-EOF.

READ INFL

AT END

IF READ-COUNT < 1

DISPLAY 'NO RECORDS PRESENT'

GO TO EXIT-PARA

END-IF

NOT AT END

PERFORM WRITE-PARA THRU WRITE-EXIT-PARA

END-READ

END-PERFORM.

PROCESS-EXIT-PARA.

EXIT.

WRITE-PARA.

ADD 1 TO READ-COUNT.

IF STORE-ID > 12346

MOVE "|" TO DELIMIT

MOVE STORE-ID TO O-STORE-ID

MOVE ITEM-ID TO O-ITEM-ID

WRITE OUTFL-REC

DISPLAY 'HI'

END-IF.

WRITE-EXIT-PARA.

EXIT.

CLOSE-PARA.

CLOSE INFL.

CLOSE-EXIT-PARA.

EXIT.

EXIT-PARA.

EXIT PROGRAM.

THE OUTPUT WILL BE

000001 12347 | DETR12347

000002 12348 | JKLH67545

000003 12350 | KLJ443232

Relative File Handling in COBOL

The relative file is also known as relative record data set or RRDS-file.

The record in these files can be accessed by - RRN (Relative Record Number)

It contains both random and sequential access.

The record can be accessed in any order by declaring a 'RECORD KEY'. The key should be a numeric constant.

SYNTAX =>
FORMAT 1)

SELECT Logical - fl ASSIGNED TO physical - fl

ORGANIZATION IS RELATIVE

ACCESS MODE IS SEQUENTIAL

RECORD KEY IS R - KEY

FORMAT 2)

SELECT Logical - fl ASSIGNED TO physical - fl

ORGANIZATION IS INDEXED

ACCESS MODE IS RANDOM

RECORD KEY IS R - KEY

R - KEY must be defined in FD clause in the FILE SECTION.

Example:

Suppose we have a data of 9000 file record

SELECT Logical - fl ASSIGNED TO physical - fl

ORGANIZATION IS RELATIVE

ACCESS MODE IS SEQUENTIAL

RECORD KEY IS R - KEY

FD LOGICAL - FL.

01 LOGICAL - FL - REC

05 R - KEY PIC 9(4)

05 R - NAME PIC X(20)

In order to hold 1000 records, we must define the key with PIC clause 9 (4) that can hold a value from 0001 to 9999.

# data[].attributes.attachment_link.title
COBOL Sequential and Relative File - Tutorial And Example

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Sequential file handling in COBOL Sequential file is also known as a flat-file. It stores records in a sequential manner, i.e., one after another, stacked. In this, we cannot directly access to the Nth record. For this, we have to read the records till N-1th before proceeding to the Nth record.

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The Boyer Moore algorithm is a searching algorithm in which a string of length n and a pattern of length m is searched. It prints all the occurrences of the pattern in the Text.

Like the other string matching algorithms, this algorithm also preprocesses the pattern.

Boyer Moore uses a combination of two approaches - Bad character and good character heuristic. Each of them is used independently to search the pattern.

In this algorithm, different arrays are formed for both heuristics by pattern processing, and the best heuristic is used at each step. Boyer Moore starts to match the pattern from the last, which is a different approach from KMP and Naive.

Let us now understand the bad character heuristic :

Bad character: A character in the Text that has no match with the pattern is called a bad character.

Now, when there is a case of mismatch, we shift the pattern until it becomes a match, and the pattern moves past the mismatched character.
MISMATCH BECOMES A MATCH
Find the position of the last character that mismatched in the pattern and, then shift the pattern until it gets aligned to the mismatched character in the Text.

Example: In the above Text, there is a mismatch at position 3( A does not match with G). Now we find the last occurrence of A in our Text. At position 1, We get the A now we shift the pattern to position 1.
PATTERN MOVE PAST THE MISMATCH CHARACTER
We look up the last occurrence of the character that does not match the pattern; if it does not exist in the pattern, we move the pattern past that last mismatched character.

Example: At position 7 there is a mismatch of character "C". It does not exist in the pattern, so we shift the pattern past 7. On shifting the pattern past 7 we get a perfect match.

Thus we find the last occurrence of every possible character in an array of size equal to alphabet size. If not present, we shift the pattern by m size.

This bad character approach takes O (n/m) time complexity in the best case.
C++ code: C code:
The Bad character approach takes O(nm) time in the worst case when all characters in the Text are the same as the pattern.

As we have discussed the bad character heuristic approach, Now, understand the Good suffix approach.

This approach also calculates a preprocessing table.
Good suffix approach
Let T be the substring of Text that matches with any substring in the pattern P.

Now we shift the pattern until:

1. Another occurrence of T in P matches with T in the Text.

2. A prefix of Pattern P that matches the suffix of T.

3. P moves past T.

Another occurrence of T in P matches with T in the Text.
There can be few more occurrences of T in our pattern. In such a scenario, we shift the pattern to align it with T.

For example, there is a substring in Text ("AB") at index 3 and 4 that matches with the pattern. So we shift our pattern to the positions where the substring lies in order to match.
A PREFIX OF PATTERN THAT MATCHES WITH SUFFIX OF T IN THE TEXT
If the above case fails anyhow, we will match the suffix of T in the prefix of our pattern. If it exists, we will align the pattern with the suffix.

For example, The suffix "BAB" matches with the prefix of the pattern("AB") at position starting from 0. We then align the pattern with the matching "AB" suffix of the Text.
PATTERN MOVES PAST T
If the above cases don't work, we shift the pattern past the T.

For example, Here, both the above cases fail because of no occurrence of T in P and no prefix in pattern match with a suffix of T. In such a case, we move the index past 4.
STRONG GOOD SUFFIX HEURISTICS
Consider a case where a substring Q(P[i to n]) got matched with T in Text, but the (i-1)th character in P is a mismatch. Now unlike case 1 we will search for T in P, which is not preceded by (i-1)th character.

For example, positions 7 and 8 matches with Text and pattern. The (i-1)th character mismatch is "C". Now, if we start searching t in P, we will get the first occurrence of t starting at position 4. But this occurrence is preceded by "C", so we will skip this and carry on searching. At position 1 we got another occurrence of t (in the yellow background). This occurrence is preceded by "A" (in blue), which is not equivalent to "C".

This results in a shift of pattern P 6 times to align this occurrence with T in Text. This is done as character "C" causes the mismatch. Therefore, any occurrence of T preceded by "C" will again cause a mismatch when aligned with t, so that's why it is better to skip this.
PREPROCESSING FOR THE GOOD STRING SUFFIX
Create an array shift. Shift[i] will contain the distance our pattern will shift if there is a mismatch at (i-1)th position.

PREPROCESSING FOR STRONG GOOD SUFFIX

Border: It is a substring that is both a proper prefix and suffix. For example, in string "ccacc", "c" is a border, "cc" is a border because it appears in both ends of the string, but "cca" is not a border. As a part of preprocessing an array bopos (border position) is calculated. Each entry bopos[i] contains the starting index of the border for the suffix starting at index i in given pattern P.

The suffix φ beginning at position m has no border, so b0pos[m] is set to m+1, where m is the length of the pattern. The shift position is obtained by the borders, which cannot be extended to the left.

The Following is the code for preprocessing:

Explanation: Consider pattern P = "ABBABAB", m = 7.

The longest region of suffix "AB" beginning at index i = 5 is φ (nothing) starting at position 7 so bopos[5] = 7.

At index i = 2 the suffix is "BABAB". The widest border for this suffix is "BAB" starting at position 4, so j = bopos[2] = 4.

Let's understand it with an example:

If character # Which is at position i-1 is equivalent to the character? at index j-1, what will the border be? + border of suffix at position i, which is starting at position j, which is equivalent to saying that border of suffix at i-1 begin at j-1 or bopos[ i-1 ] = j-1 or in the code:
i-; j-; bopos[ i ] = j
But if character # at position i-1 does not match with the character at position j-1, then we continue our search to the right. Now, we know that:

1. Border width will be smaller than the border starting at position j, i.e. smaller than x...φ

2. Border has to begin with # and end with φ or could be empty (no border exists).

With the above two facts, we will continue our search in substring x...φ from position j to m. The next border will be at j = bopos[j]. After updating j, we again compare characters at position j-1 (?) with #, and if they are equal, then we got our border; otherwise, we continue our search to the right until j>m. This process is shown by code -

In the above code, look at the following conditions:
pattern[i-1] != pattern[j-1]
This is the condition which we discussed in case 2. When the character preceding the occurrence of t in pattern P is different from the mismatching character in P, we stop skipping the occurrences and shift the pattern. Here P[i] == P[j] but P[i-1] != P[j-1] so the pattern shifts from i to j. So shift[j] = j-i is a recorder for j. So whenever any mismatch occurs at position j, we will shift the pattern shift[j+1] positions to the right.

In the above code the following condition is very important:
if (shift[j] == 0 )
This condition prevents modification of shift[j] value from suffix having the same border.
2) Preprocessing - Case 2
The widest border of the pattern that is contained in that suffix is found, and the starting position of the widest border is stored in bopos[0].

In the following algorithm, this value bopos[0] is initially stored in all free entries of array shift. When the suffix of the pattern becomes smaller than bopos[0], the algorithm moves forward with the next-wider border of the pattern, i.e., with bopos[j].
C code: C++ code:

# data[].attributes.attachment_link.title
Boyer Moore Algorithm - Tutorial And Example

# data[].attributes.attachment_link.description
The Boyer Moore algorithm is a searching algorithm in which a string of length n and a pattern of length m is searched. It prints all the occurrences of the pattern in the Text. Like the other string matching algorithms, this algorithm also preprocesses the pattern.

# data[].attributes.attachment_link.readable_text
In general, Jenkins uses the master-slave architecture to develop software. Jenkins agents are nothing, but probably you can say that Jenkins slaves are Jenkins agent.

Jenkins agents are like a machine or Container, which connects with the Jenkins master to execute the build on his command.
Difference between top and stage level agent:
There is a slight difference between the top level and stage level Jenkins agent. These agents are used in the declarative pipeline process. The main difference between them is:

1. The top-level section must be defined at the top of the pipeline block, but the stage level can be defined anywhere in the pipeline block.

2. In the top-level agent, options are invoked after entering the agent, while in stage level, options are invoked before entering the agent.

Jenkins Remoting:

It is a library and executable java backlog used to establish the communication layer in the Jenkins tool. Jenkins remoting is mainly used in master-slave communications. It works on TCP/IP communication protocol, remote procedural calls, data streaming, class loading and many more.

Remoting library is used in establishing the connection between Jenkins master, JNLP and SSH agents with the help of TCP/IP protocol.

Docker:

Docker is a platform used to deliver software tools from company to market in the form of packages. These packages are known as containers. One Container keeps it separate from another container. They are joined with their software tool and their libraries.

Docker was found by Soloman Hykes in 2010, but it made its official debut in 2013, and this time, it got fully introduced in the market.

Jenkins with docker: without docker, you need to install some additional tools and different agents in Jenkins. Jenkins pipeline works very well with docker container.

Deploying Docker containers is very easy as you can deploy them on any physical machine and virtual machine. You can also deploy it on the cloud.

Python API:

Jenkins also supports python. You can also perform the same operation in python as you do in java with the help of python API. Internally python uses rest APIs to perform such operations. You need to install the Jenkins with the help of the pip command, and then you can import the Jenkins module from the Jenkins server to perform operations in python.

Write the following command on CMD:

$ pip install - -user python-Jenkins

$ python

Now, go in python idle and type the given statement:

>>> from jenkins import Jenkins

>>> help(Jenkins)

The above statement will show you all the magic functions classes and normal functions related to Jenkins. By using all these facilities you can easily perform operations with jenkins

You can also see other information like copyright, credit, license and many more by following the given structure:

>>> help(Jenkins)

>>> copyright(Jenkins)

>>> credits(Jenkins)

>>> license(Jenkins)

Get jobs from Jenkins using python API:

>>> from jenkins import Jenkins

>>> j = Jenkins(url = 'http://YOUR_ENKINS_HOST_NAME', username = 'YOUR_USERNAME', password = 'YOUR_API_TOKEN')

>>> j.get_whoami()

>>> j.get_all_jobs()

Purpose of creating Blue Ocean:

1. Make it easier for teams to use Jenkins.

2. Easy access to jobs for every team member.

3. Provide a better user interface.

Browser compatibility:

All the browsers are supportable for Jenkins, but there are some plug-ins that will not work properly with some browsers like:

Blue Ocean plug-in is not yet runnable in Internet explorer and AmigaOS. Blue Ocean's dashboard does not support these browsers at the current time.

Reporting bugs and feature request:

We use Jenkins JIRA for it.

Create a new account, browse in JIRA and login with your account, then create a new problem with the component >> blue ocean-plugin.

Jenkins in Future:

The future of Jenkins is very bright in the market. Even now, it comes in the most popular CI tool available in the market. It has great support from the developer's community. Although there are some cons of the Jenkins, sooner it will overcome them.

Continuous integration and continuous delivery have changed the model of the market in the last few years. The CI and CD was the new concept when Jenkins was introduced in the market, but it has made its own space in the market. Jenkins fully works on Continuous integration and continuous deployment method, so it becomes very popular among the developer in very little time after its release.

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In general, Jenkins uses the master-slave architecture to develop software. Jenkins agents are nothing, but probably you can say that Jenkins slaves are Jenkins agent. Jenkins agents are like a machine or Container, which connects with the Jenkins master to execute the build on his command.

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The main aim of machine-independent optimization is to improve the generated intermediate code so that compiler can get better target code.

Eliminating unwanted code from the object code or replacing one set of code with another set of code, which makes the object code faster without changing the result of object code, is generally called code improvement or code optimization.

A high-level language can have run-time overhead. Writing a program in a high-level language can cause redundancy. Code optimization will allow us to remove these inefficiencies.

Optimized code will use less space and makes the program execution fast. The optimized code can be re-used.

Code optimization can be performed in the following ways:
Compile Time Evaluation
Perform 4*(19/0.5)*r at compile time

2) a = 5

b = a/6

Perform a/6 as 5/6 at compile time
Global Common Subexpressions
Any expression can be known as a common subexpression if the value of an expression is previously computed. And the value of the variable in expression has not changed since the previous computation.
Example
p = x * y

q = x

r = q * y + 9

After the optimization of code:

p = x * y

q = x

r = x * y + 9

Here, after variable propagation, x * y and q * y identified as common sub-expression.
Dead-Code Elimination
If any variable's value can be used anywhere in the program, then the variable will be called live at a point in a program; otherwise, it will be termed as dead code. A dead code is not added intentionally by the programmer in any program. It may be the result of the previous computation.
Example
Before the elimination of code:

p = x * y

q = x

r = q * y + 9

After the elimination of code:

p = x * y

r = q * y + 9

In this example, q = x is a dead code because there is no use of this code in the program.
Code Motion
Loops have a very important place for optimizations, mostly in the inner loops where programs tend to spend a lot of their time. A program's run time complexity may be improved by decreasing the amount of code in an inner loop, even if we increase the amount of code outside that loop.

Code motion reduces the number of code in a loop. This optimization computes a loop-invariant statement outside the loop.
Example
Evaluation of limit - 2 in the following while-statement:

while (i <= limit - 2)

This code will be further optimized as:

t = limit-2

while (i <= t)

After the optimization, limit-2 is computed only one time before entering the loop. Previously there would be n +1 calculations of limit-2 if we iterated the body of the loop n times.
Induction Variables and Reduction in Strength
Optimization of induction variables inside a loop is also an important optimization. Any variable of the form x = x + constant is induction variable.

Induction variables can be computed with a single increment per loop iteration.

Replacing an expensive operator with low strength is strength reduction.
Example
Before the reduction, code is:

i= 2;

while(i<10)

{

y = i * 6

}

Code, after the reduction:

i=2

x = 6

{

while(x<30)

y =x;

x = x +4:

}

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Machine-Independent Optimizations in Compiler Design - Tutorial And Example

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The main aim of machine-independent optimization is to improve the generated intermediate code so that compiler can get better target code. Eliminating unwanted code from the object code or replacing one set of code with another set of code, which makes the object code faster without changing the result of object code, is generally called code improvement or code optimization.

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All the optimization techniques we have learned earlier depend on data flow analysis. DFA is a technique used to know about how the data is flowing in any control-flow graph.

Forglobal common sub-expression elimination, we need to find the expression that computes the same value along with any available execution path of the program.
The Data-Flow Analysis Schema
In data flow analysis, a data flow value associates with every program point represents an abstraction for a set of all possible program states for that point.

The domain of this application is a set of possible data flow values.

IN[a]: The data flow value before the statement a.

OUT[a]: The data flow valueafter the statement a.

The main aim of the data flow problem is to find a set of constraints on the IN[a]'s and OUT[a]'s for statements a.

There are two sets of constraints: Transfer function and control-flow constraints.

Transfer Function

The semantic of the statement are the constraints for the data flow values before and after a statement.

For example, if variable x has the value y before executing any statement, say p = x. Then, after the statement's execution, the value for both x and p will be y.

The transfer function is the relationship between the data flow values before and after the assignment statement.

Transfer function comes in two ways:

Forward propagation along with execution path

Backward propagation up the execution path

Forward Propagation:

The following points should be considered:

In forward propagation, the transfer function for any statement s will be represented by Fs.

This transfer function takes the data flow values before the statement and produces the output or new data flow value after the statement.

So the new data flow values after the statement will be OUT[s] = Fs (IN[s]).

Backward propagation:

The following points should be considered:

Backward propagation is the converse of forward propagation.

This transfer function converts a data flow value after the statement to a new data flow value before the statement.

So the new data flow values will be IN[s] = Fs (OUT[s]).

Control-Flow Constraints

The second set of constraints is derived from the flow of control. If block B consists of statements S1, S2, ........, Sn, then the control flow value of Si will be equal to the control flow values into Si + 1. Which is:

IN [ Si +1 ] = OUT [ Si ], for all i = 1 , 2, .....,n - 1.

Reaching Definition

The most common and useful data flow scheme is Reaching Definition. A definition D reaches the point P along with path following D to P such that D is not killed along the path.

Live-Variable Analysis

Here we know about the value of a variable at point p is used from point p to the end. It means that the variable is live at point p; otherwise variable is dead at point p.

This is used for register allocation for basic blocks.

Available Expressions

An expression a + b is said to be available at point p if all the path from entry node p evaluates a + b. There should not be any other assignment to a or b.

We can say that block kills expression a + b if it assigns a or b and does not computes a + b.

The main use of the available expression is to detect global common sub-expression.

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Data Flow Analysis in Compiler Design - Tutorial And Example

# data[].attributes.attachment_link.description
All the optimization techniques we have learned earlier depend on data flow analysis. DFA is a technique used to know about how the data is flowing in any control-flow graph. Forglobal common sub-expression elimination, we need to find the expression that computes the same value along with any available execution path of the program.

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Basic Blocks and Flow Graphs in Compiler Design

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Basic Blocks and Flow Graphs in Compiler Design

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In this section, we are going to learn how to work with basic block and flow graphs in compiler design.

Basic Block

The basic block is a set of statements. The basic blocks do not have any in and out branches except entry and exit. It means the flow of control enters at the beginning and will leave at the end without any halt. The set of instructions of basic block executes in sequence.

Here, the first task is to partition a set of three-address code into the basic block. The new basic block always starts from the first instruction and keep adding instructions until a jump or a label is met. If no jumps or labels are found, the control will flow in sequence from one instruction to another.

The algorithm for the construction of basic blocks is given below:

Algorithm: Partitioning three-address code into basic blocks.

Input: The input for the basic blocks will be a sequence of three-address code.

Output: The output is a list of basic blocks with each three address statements in exactly one block.

METHOD: First, we will identify the leaders in the intermediate code. There are some rules for finding leaders, which are given below:

1. The first instruction in the intermediate code will always be a leader.

2. The instructions that target a conditional or unconditional jump statement are termed as a leader.

3. Any instructions that are just after a conditional or unconditional jump statement will be a leader.

Each leader's basic block will have all the instructions from the leader itself until the instruction, which is just before the starting of the next leader.

Consider the following source code for a 10 x 10 matrix to an identity matrix.

The three address code for the above source program is given below:

According to the given algorithm, instruction 1 is a leader.

Instruction 2 is also a leader because this instruction is the target for instruction 11.

Instruction 3 is also a leader because this instruction is the target for instruction 9.

Instruction 10 is also a leader because it immediately follows the conditional goto statement.

Similar to step 4, instruction 12 is also a leader.

Instruction 13 is also a leader because this instruction is the target for instruction 17.

So there are six basic blocks for the above code, which are given below:
B1 for statement 1 B2 for statement 2 B3 for statement 3-9 B4 for statement 10-11 B5 for statement 12 B6 for statement 13-17.
Flow Graph

It is a directed graph. After partitioning an intermediate code into basic blocks, the flow of control among basic blocks is represented by a flow graph. An edge can flow from one block X to another block Y in such a case when the Y block's first instruction immediately follows the X block's last instruction. The following ways will describe the edge:

There is a conditional or unconditional jump from the end of X to the starting of Y.

Y immediately follows X in the original order of the three-address code, and X does not end in an unconditional jump.

Flow graph for the 10 x 10 matrix to an identity matrix.

Block B1 is the entry point for the flow graph because B1 contains starting instruction.

B2 is the only successor of B1 because B1 doesn't end with unconditional jumps, and the B2 block's leader immediately follows the B1 block's leader.

B3 block has two successors. One is a block B3 itself because the first instruction of the B3 block is the target for the conditional jump in the last instruction of block B3. Another successor is block B4 due to conditional jump at the end of B3 block.

B6 block is the exit point of the flow graph.

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Basic Blocks and Flow Graphs in Compiler Design - Tutorial And Example

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In this section, we are going to learn how to work with basic block and flow graphs in compiler design. The basic block is a set of statements. The basic blocks do not have any in and out branches except entry and exit.

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In this topic, we will be making a complete COBOL database program with all the properties that we have learned earlier. With this, you will get a complete idea about how to run a project in COBOL language.

You will be provided with all JCB commands to proceed further.