Delphi Programming: Strings, Parameters, and Functions

1. Understanding Short and Long Strings

Short strings have a fixed length, not exceeding 245 characters. They are declared as follows:

• VAR S1: ShortString;
• VAR S2: STRING[25];

Long strings are allocated dynamically and are limited only by available memory. They are declared as:

• VAR S1: STRING;

2. What Are Parameters?

A parameter is a value passed to a function or procedure to be processed.

3. Parameter Passing: Value vs. Reference

Passing by Value: A copy of the original variable is created; the original value remains unchanged.

Passing by Reference: No copy is created; the procedure works directly with the original variable.

• Value: PROCEDURE REVIEW(NAME: STRING);
• Reference: PROCEDURE REVIEW(VAR NAME: STRING);

4. Functions vs. Procedures

• Function: A code section that performs an operation and returns a value.
• Procedure: A code section that performs an operation but does not return a value.

5. How Do Functions Return Values?

Functions return values by assigning the result to a local variable named Result or by assigning it to the function name itself.

6. Purpose of INC and DEC Functions

• INC: Increments a numeric variable. Example: INC(X);
• DEC: Decrements a numeric variable. Example: DEC(X);

7. Checking for Empty Components

To check if a Label1 component is empty (ignoring spaces):

IF Length(Trim(Label1.Caption)) = 0 THEN ShowMessage('Empty');

8. Common String and Conversion Commands

• a. Transform 'address' to uppercase: address := UPPERCASE(address);
• b. Transform 'X' to lowercase: X := LOWERCASE(X);
• c. Convert REAL variable to STRING: NAME := FLOATTOSTR(NUM);
• d. Convert STRING to INTEGER: NUM := STRTOINT(EDIT5.TEXT);
• e. Extract characters using COPY: xyz := COPY(abc, 5, 3);