Comments in different Programming Languages

Comments are helpful medium for storing useful information in application codes while developing it. A successful software is not only represented by how well it does it task but also by how well it is documented and how well it's programming logic can be understood by a new comer. So, the software enhancements can be supported by new comer, which helps in long run of the software.

 

Without writing any further on its usefulness, I will directly move to the topic. There are two types of comments in programming languages. One is single line comment, which works for the line where it is given. It usually has starting mark but no ending mark. Other is multi-line comment, which works for until the closing mark is found.

 

Comment in C, C++, C#, PHP

A single line comment is preceded by double slash (//).  An example is shown below.

 

//function to reverse an array

Int reverse(int a[])

{

            //code goes her

}

No doubt, you can use double slash to comment multiple consecutive lines provided that each line is preceded by double slash (//).

Multi-line comment starts with single slash and an asterisk sign (/*) and ends with (*/).

 

Int reverse(int a[])

/*function to

            reverse an array */

 

This commenting style is applicable for many programming languages.

 

Comment in VB, ASP, VBScript

Single line comment is preceded by single apostrophe (').

 

Comment in SQL Server

Single line comment is preceded by double dash (--) while multi-line comment is represented by text between (/*) and (*/) marks.

If you give comment inside comment, then also whole thing is represented as comment.

 

Comment in HTML

Multi-line comment begins with (<!--) and ends with (--!>). An example is shown below.

<!--<div id="footer">                   

                    ©2008 Aptech Suraj Lubhu

                </div>-->

 

Comment in JavaScript

Comment in JavaScript is similar as in C and C++. Single line comment is preceded by double slash (//) while multi-line comment begins with (/*) and ends with (*/) marks.

 

Comment in CSS Style Sheets

Multi-line comments in CSS are preceded by (/*) and followed by (*/).

 

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Paging in Web Applications (SQL Trick)

Web Applications here means the applications that are used through browsers. Web applications are tougher to develop and use as compared to windows applications. In this topic, I want to put focus on paging techniques for web applications.

If you are a web programmer, you may be having problem to display a large report or data in a data grid with paging. Paging is required as it might not be practical to display large no. of rows in a single grid. User will have to keep scrolling down and up. Also, a large memory will be constantly consumed. There are no. of ways to use paging in data grids. Here, I would like to focus on data grid displayed by pulling data from RDBMS database like SQL Server.

Suppose you are running a stored procedure (say sp_report1) to pull data from SQL Server database and it returns all data (say 5000 rows) at one time. A simple way would be to pass two input variables like @from_row_no and @to_row_no to the procedure and modify it to return rows of data from @from_row_no to @to_row_no.

This also can be done two ways. In first way, you put all output data in a temporary table which also contain an identity column. Then, while running final select statement from that final output table, use conditions to display from @from_row_no to @to_row_no.

Here is an example.

Create proc sp_Report1

( @from_row_no int, @to_row_no int)

as

begin

create table #tbl_final_display

(

id  int identity(1,1),

col1 varchar(30),

col2 varchar(30)

)

/* now insert data into #tbl_final_display as per your requirement */

-- for final select

select *

from #tbl_final_display

where id >= @from_row_no

and id <= @to_row_no

end

If you have to display results in order then you will have to pass ordering column name also to stored procedure. If the data in #tbl_final_display is going in single statement you can use order by clause in that statement with passed input variable. If not, you will have to create two temporary tables. First one to just hold the data and second one to copy data from first one by using order by clause. The second table will obviously have one more column than first one for id field. This process becomes tedious when there are many sortable columns as many if else conditions are required.

Here "id int identity(1,1)" means that id column of the table will have datatype int and the values will be automatically inserted while inserting rows in that column. The values will start from 1 and will keep on increasing by 1 for each new row.

In Second Method, you need to use the permanent table in which data are kept temporary. The stored procedure will just populate the table. Final select from table is run from front end like this.

For example to retrieve data from table tbl_final_display from row 9 to row 14 order by first field, you can use this query.

select    *
from    (
    select    top 6 *
    from    (
        select    top 14 *
        from    tbl_final_display
        order by 1
    ) tmp
    order by 1 desc
    ) tmp
order by 1

It uses multiple sub-queries and multiple select. First it selects 14 rows (@to_row_no) and then selects last 6 rows from that select. This has to be done from front end as while using "top 6 " we cannot pass variable instead of 6. It may be tedious for programmers to handle from front-end as much additional care must be taken. Such as provide fields to distinguish multiple users to eradicate the chances of wrong output when same report is used by multiple users.

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