Assembly Language DB Question

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Hi,

Lately I have been Studying some Assembly language, I have a question about the DB Decleration on the .Data Segment of an Assembly Application.

Till Now, I always declared a Byte by doing So:

Number db "Please enter a number : ",0

(Name) db (String), 0

Today, I found an example which had the String Declaration as Follows:

Hello db "Hello World!",13,10, 0

I Have a Question Regarding the 13, 10.

Can anybody point out what these mean.

Thank You,

Andrew Borg

Posted 9-Oct-12 20:31pm

Andrew_Borg

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Sergey Alexandrovich Kryukov 10-Oct-12 2:46am

Never heard of 13 10, really? :-)
--SA

2 solutions

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OriginalGriff · Accepted Answer · 2012-10-09T20:45:00

Solution 1

:laugh:
They are bytes values added to the end of the string, that cannot be added by normal typing. In this case a carriage return, a line feed and a terminating null character.
In C-type languages, this would be the equivalent of writing:

C++

char* Hello = "Hello World!\n";

It is a good idea to declare these as mnemonics though, so you can use readable names instead of numbers:

Hello db "Hello World!", AS_CR, AS_LF, 0

(I probably wouldn't use AS_NULL for the zero, as it would most likely be a string terminator, rather than a character to display)

Posted 9-Oct-12 20:45pm

OriginalGriff

Comments

pasztorpisti 10-Oct-12 4:09am

+5, but for the clarification of OP its important to note that "Hello World!\n" produces "Hello World",10,0 with all C compilers on all platforms, its just the standard library that interprets the '\n' (10/LineFeed/LF) character and outputs either 10(linux) or 13(mac) or 13,10(DOS/Windows) when writing the string into a stream in TEXT mode (not binary because that doesn't do the conversion!!!). The standard library also does the conversion of these into 10 when reading from a file.

Sergey Alexandrovich Kryukov · Accepted Answer · 2012-10-09T20:46:00

Solution 2

They mean CR LF, Carriage_Return (13), Line_Feed (10). These two bytes together define standard end-of-line delimiter in ASCII (or any one-byte-per-character encodings) in case of Microsoft systems.

(Generally, the end-of-line delimiter is platform-dependent; and this fact used to be a source on numerous confusions, which appear not often, but from time to time even these days.)

—SA

Posted 9-Oct-12 20:46pm

Sergey Alexandrovich Kryukov

Comments

pasztorpisti 10-Oct-12 4:10am

+5

Sergey Alexandrovich Kryukov 10-Oct-12 10:51am

Thank you :-)
--SA