How do i Comment in various Programming Languages
Comment is all about the text which you want to write your own descriptions of the code that compiler ignore. It is always added to make the code understandable. The Syntax and rules for comments vary language to language.
Comments are generally formatted as block comments (also called prologue comments or stream comments) or line comments (also called inline comments).
Block comments delimit a region of source code in which the region is allowed to span multiple lines. This region is specified with a start delimiter and an end delimiter. Some programming languages (such as MATLAB) allow block comments to be recursively nested inside one another, but others (such as Java) do not.
Line comments either start with a comment delimiter and continue until the end of the line, or in some cases, start at a specific column (character line offset) in the source code, and continue until the end of the line.
Some programming languages employ both block and line comments with different comment delimiters. For example, C++ has block comments delimited by /* and */ that can span multiple lines and line comments delimited by //. Other languages support only one type of comment. For example, Ada comments are line comments: they start with — and continue to the end of the line.
These are the following programming languages with comments type:
1. C
// this line will be ignored by the compiler /* these lines will be ignored by the compiler */ x = *p/*q; /* note: this comment starts after the ‘p’ */
2. C++
/* This is a single line comment */
// This is a single one line comment
/* This is a multiple line comment*/
3. C#
///<summary>
///summary description
///</summary>
/* This is a multi-line comment and continues until the end
of comment symbol is reached */
4. Java
/**
* Registers the text to display in a tool tip. The text
* displays when the cursor lingers over the component.
*
* @param text the string to display. If the text is null,
* the tool tip is turned off for this component.
*/
public void setToolTipText(String text) {
5. VB
‘ Requirements:
‘ Requires advapi.dll and Windows 98/NT+
‘ ********************* Comments
In VB There is no multiline commentapostrophe is the only comment marker in vb.
net
6. HTML
<!–This is a comment. Comments are not displayed in the browser–>
7. XML
The syntax for writing comments in XML is similar to that of HTML.
<!– This is a comment –>
8. ASP
<%
‘Hello I am a comment
Dim newVar1, newVar2
‘Dim oldVar1, oldVar2
%>
9. PHP
In PHP, we use // to make a one-line comment or /* and */ to make a comment block:
10. Unix Shell Scripts
Comment lines in unix Shell script start with a hash character.# commentmycommand myparameters
# comment
There is no multiline comment option in shell scripting
Alternatively we can use this
: <<‘END’
comments’ here
and here
END
Reference: http://www.unix.com/shell-programming-scripting/39478-block-comment-shell-script.html
11. Oracle
With /*…*/, as in C.
With a line that begins with two dashes –.
Thus:
— This is a comment
SELECT * /* and so is this */
12. SQL
Comments in SQL are in single-line-only form, when using two dashes:
— This is a single line comment
— followed by a second line
SELECT COUNT(*) FROM Authors
WHERE Authors.name = ‘Smith’; — Note: we only want ‘smith’
— this comment appears after
SQL code
The syntax for Transact-SQL also supports alternative formats for specifying
comments. One format supported by this syntax is identical to the “block
comment” style used in the syntax for C++ and Java.
/*This is a comment line 1This is a comment line 2*/
SELECT COUNT(*) FROM Authors
13. F#
//singleline commment
(* This is a comment *)
(* Sample hello world program *)
printfn “Hello World!”
14. Matlab
Comment lines begin with the character ‘%’, and anything after a ‘%’
character is ignored by the interpreter. The % character itself only tells the
interpreter to ignore the remainder of the same line.
% Calculate average velocity, assuming acceleration is constant% and a
frictionless environment.
15. Cold Fusion
<!— This prints “Hello World” to the browser. —>
<cfoutput> Hello World<br /> </cfoutput>
16. Fortran IV
C
C Lines that begin with ‘C’ (in the first or ‘comment’ column) are comments
C
WRITE (6,10) 10 FORMAT(12H HELLO WORLD) END
17. Fortran 90
!* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
!*All characters after an exclamation mark are considered as comments *
!* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
PRINT “WIKIPEDIA” ! Fortran 90 introduced the option for inline comments.
END
18. Objective CAML
codeLine(* comment level 1(*comment level 2*)*)
19. Perl
#!/usr/bin/perl
my $s = “Wikipedia”; # Sets the variable s to “Wikipedia”.
print $s . “\n”; # Add a newline character after printing for shells that do not do so automatically.
20. Python
#!/usr/bin/env python
# this program prints “Hello World” to the screen and then quits.
print “Hello World!”
def foo(x, y):
”’Frobnicate the bar and baz
together with one another”’
return frob(frob(x), frob(y))
21. Ruby
Single line commenting: (line starts with hash “#”)
puts “This is not a comment”
#this is commented
puts “This is not a comment”
Multi-line commenting: (comments goes between keywords “begin” and
“end”)
puts “This is not a comment”
=begin
whatever goes in here
will be ignored 🙂
=end
puts “This is not a comment”
22. Haskell
Single line comments in Haskell start with ‘–‘ (two dashes), and multiple line comments start with ‘{-‘ and end with ‘-}’.
{- this is a comment
on more lines -}
— and this is a comment on one line
putStrLn “Wikipedia”
23. Basic Classic
In FORTRAN, BASIC, and COBOL languages, comments are full lines; and each
comment is begun by a specific comment mark in a fixed position on the line. In
BASIC, REMark lines start with REM.
010 REM FIND PRIME NUMBERS LESS THAN 100
020 REM BY DENNIE VAN TASSEL
030 REM JULY 4, 1965
040 LET A = 1
24.COBOL
COBOL has a similar style of comments. An asterisk has to be put in position 7, and then the rest of the line is a comment. COBOL labels have to start in position 8 or later, and COBOL statements have to start in position 12 or later. Here are how comments would look in COBOL:
010010* FIND PRIME NUMBERS LESS THAN 100
010020* BY DENNIE VAN TASSEL
010030* JULY 4, 1959
010035 START-LOOP.
010040 MOVE 1 TO A.
25. Assembly Language
End of line comment
; (semicolon)
26. MYSQL
MySQL Server supports three comment styles:
From a “#” character to the end of the line.
From a “– ” sequence to the end of the line. This style is supported as of
MySQL 3.23.3. In MySQL, the “– ” (double-dash) comment style requires the
second dash to be followed by at least one whitespace or control character
(such as a space, tab, newline, and so on). This syntax differs slightly from
standard SQL comment syntax, as discussed in Section 1.9.5.8, “’–‘ as the
Start of a Comment”.
From a /* sequence to the following */ sequence, as in the C programming
language. This syntax enables a comment to extend over multiple lines because
the beginning and closing sequences need not be on the same line.
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