Summary
Highlights
A practical example shows how to extract and display a single character from a string using its index. For instance, `StTemp[5]` for 'hello world' will display 'o'.
Functions return a single value. The `Length` function returns the number of characters in a string as an integer. For 'hello world', `Length(StTemp)` would return 11. It's necessary to convert this integer to a string for display in functions like `ShowMessage`.
A string in Delphi represents text, which can include numbers. Delphi breaks strings into individual characters, each with its own ASCII value. Characters can be accessed using square brackets and their position, similar to array indexing (e.g., StTemp[5] returns the fifth character).
The `Pos` function takes two string parameters: a substring to search for and the main string. It returns an integer representing the starting position of the first occurrence of the substring within the main string. If the substring is not found, it returns 0. Case sensitivity is important; 'w' is different from 'W'.
The `Copy` function extracts a portion of a string. It takes three parameters: the source string, the starting position, and the number of characters to copy. For example, `Copy(StTemp, 3, 5)` from 'hello world' starts at position 3 ('l') and copies 5 characters ('llo w'), returning 'llo w'. If the number of characters to copy exceeds the string's length from the starting position, it copies until the end without error.
The `UpCase` and `LowCase` functions convert all characters in a string to uppercase or lowercase, respectively. They take a single string parameter and return a new string with the converted case. The original string remains unchanged; the result is stored in a new variable.
A recap of the discussed string functions: `Length` and `Pos` return integers, while `Copy`, `UpCase`, and `LowCase` return strings. The next video in the series will cover string procedures.