What is declaration in pascal programming?

Answer 1

A "declaration" in computer programming is when you define the properties of variables or functions used in the program. Most programming languages require you to "declare" the variables to be used within the program before they are used in any calculations or other operations. For example, in the C program language, you could define a variable like this: float distance; this declares a variable called "distance" and says that it is a "floating point" variable, that is, a numeric value, with optional decimal places. If we declare two other variables, and give them the names "speed" and "time", we can then use them within the main program, like this: distance = speed * time; (where the "*" is used in C and most other languages to mean multiply). You are free to use abbreviations for the variables, declaring them like this: float D, S, T; and then writing the expression above as: D = S * T; but it is considered "good programming practice" to use longer, "meaningful" names, especially in longer programs, where it would make the programs easier to read, and it would make it easier to remember what the variable names stood for. As well as "float" types (which may be called "real" or "double" in other programming languages), there are also some other types: For example, "int" types (sometimes written as "integer" in other languages) are for declaring a variable to hold a whole number, one without any decimal places. An example of this might be the declarations: int goalsfor, goalsagainst, goaldiff; int points; int won, drawn, lost; which could be used in the expressions: goaldiff = goalsfor - goalsgainst; points = won * 3 + drawn; The reason for declaring the variables as "int" rather than "float" is because, logically, you can't score 1.5 or 2.736 goals, and also, because variables declared as "int" can be stored using less computer memory. Another declaration type might be a "string" or "character" type, used to store text, that is, any mixture of letters and numbers, such as names, addresses, words - anything other than numeric values. In some languages, when you declare such a text variable, you also have to say how many letters are to be allowed. For example, in C, the declarations: char firstname[12], secondname[20]; char address[50]; allows 12 letters for the firstname, 20 for the secondname, and 50 letters/and or numbers for the address. Most computer languages will give an error if you make a mistake in a declaration, or if you forget to declare the variable - this can stop you from making mistakes later. For example if you had the declaration: int numchildren, sons, daughters; and then used the expression: children = sons + duaghters; the computer would show two errors - one because you declared the variable as "numchildren", but used "children" in the expression, and secondly because you mis-spelled "daughters". As stated above, this can also apply to functions (also known as "procedures" or "subroutines"), but this a slightly more complicated topic which could be the subject of another question.

Answer 2

Declaration is where you indicate what variables are used in the unit or function/procedure.

For example, in some languages you can make up variables as you go, like the following C# example:

static void Main(string[] args)

{

string firstName = "John";

string lastName = "Doe";

}

Pascal and Delphii are strongly typed languages.

You would create the same example in pascal as

Procedure Main;

var

FirstName: string;

LastName: string;

begin

FirstName := 'John';

LastName := 'Doe';

end;

Answer 3

A declaration in assembler is simply a declaration of a named variable or constant. The symbolic names are stripped out during assembly, to be replaced with the actual memory address assigned to those variables. They simply make it easier to reference memory even when you cannot know the actual addresses in advance of assembly.