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   ► KBProgrammingDelphi for W...Language Basics   Print This    All Groups  
  From the November 2009 Issue of Prestwood eMag
 
Delphi Language Basics:
Delphi Literals (apostrophe)
 
Posted 12 years ago on 11/4/2008 and updated 1/18/2009
Delphi Code Snippet:
 A flashcard from our Delphi Flashcards Library
 A code snippet from our Delphi Code Snippets Page
 Tags: Delphi , Literals

KB101523

General Info: Programming Literals

A value directly written into the source code of a computer program (as opposed to an identifier like a variable or constant). Literals cannot be changed. Common types of literals include string literals, floating point literals, integer literals, and hexidemal literals. Literal strings are usually either quoted (") or use an apostrophe (') which is often referred to as a single quote. Sometimes quotes are inaccurately referred to as double quotes.

Languages Focus: Literals

In addition to understanding whether to use a quote or apostrophe for string literals, you also want to know how to specify and work with other types of literals including floating point literals. Some compilers allow leading and trailing decimals (.1 + .1), while some require a leading or trailing 0 as in (0.1 + 0.1). Also, because floating point literals are difficult for compilers to represent accurately, you need to understand how the compiler handles them and how to use rounding and trimming commands correctly for the nature of the project your are coding.

Delphi Literals

String literals are single quoted (the apostrophe) as in 'Prestwood'. If you need to embed an apostrophe use two apostrophes in a row.

Floating point literals must start with an integer. For example, to specify a fractional floating point literal between 1 and -1, you preceed the decimal with a 0; otherwise, you will get a compiler error.

//x := .1 + .1;   //Does not work.
x := 0.1 + 0.1;   //Does work.
Syntax Example:
ShowMessage('Hello');
ShowMessage('Hello Mike''s website.');

More Info

Definition:  Programming Literals

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Code Contributed By Mike Prestwood:

Mike Prestwood is a drummer, an author, and creator of the PrestwoodBoards online community. He is the President & CEO of Prestwood IT Solutions. Prestwood IT provides Coding, Website, and Computer Tech services. Mike has authored 6 computer books and over 1,200 articles. As a drummer, he maintains play-drums.com and has authored 3 drum books. If you have a project you wish to discuss with Mike, you can send him a private message through his PrestwoodBoards home page or call him 9AM to 4PM PST at 916-726-5675 x205.

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Linked Certification Question(s)

The following are practice certification questions with answers highlighted. These questions were prepared by Mike Prestwood and are intended to stress an important aspect of this KB post. All our practice questions are intended to prepare you generally for passing any certification test as well as prepare you for professional work.

Beginner

2 Beginner Level Questions

Question #1: Multiple Choice

Which code line correctly embeds an apostrophe?

Answer:
1. 
ShowMessage('Hello Mike\'s website.');
2. 
ShowMessage("Hello Mike's website.");
3. 
ShowMessage('Hello Mike#'s website.');
4. 
ShowMessage('Hello Mike''s website.');
5. 
ShowMessage('Hello Mike'''s website.');
Question #2: Yes or No?

If x is defined as a variable of type double, will the following compile?

x := .1 + .1;
Answer:
  • Yes
  • No

  •  KB Article #101523 Counter
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