17.1: String Class within C++
- Page ID
In most programming languages a string is typically a string of characters (string them along in a series). The rules for handling strings vary from language to language. Technically, there is no string data type in the C++ programming language. However, the concept of a string data type makes it easy to handle stings of character data. Associated with object oriented programming the string class has been added to C++ as a standard part of the programming language.
Most data is more complex than just one character, integer, etc. Programming languages develop other methods to represent and store data that are more complex. A complex data type of array is first most students encounter. An array is a sequenced collection of elements of the same data type with a single identifier name. This definition perfectly describes our string data type concept. The simplest array is called a one-dimensional array; also know as a list because we usually list the members or elements vertically. However, strings are viewed as a one-dimensional array that visualize as listed horizontally. Strings are an array of character data.
In the "C" programming language all strings were handled as an array of characters that end in an ASCII null character (the value 0 or the first character in the ASCII character code set). This changed with the implementation of the string class within C++ where strings are stored as a length controlled array with a maximum length of 255 characters. This string class implementation also allowed programmers to use the reserved word string as if it were a data type. Commonly used operators and some alternatives for the string class are summarized in the following table:
|C++ Operator||Operator Name||String Class Implementation|
|=||assignment||Same as for standard data types|
|<, >, <=, >=, ==, !=||six relational||Same as for standard data types|
|+||addition||Concatenation or Append|
|sizeof||Usage how many bytes a data type occupies||Implemented using a class member function named length. Format: identifier_name.length() NOTE: The period between the identifier name and the function name is the class member operator.|
|. (the period)||class member||Used in conjunction with class functions|
Most other operators are not allowed and basically do not make sense for a string data type. The above items are demonstrated in the following program.
Demonstration Program in C++
Creating a Folder of Sub-Folder for Source Code Files
Depending on your compiler/IDE, you should decide where to download and store source code files for processing. Prudence dictates that you create these folders as needed prior to downloading source code files. A suggested sub-folder for the Bloodshed Dev-C++ 5 compiler/IDE might be named:
If you have not done so, please create the folder(s) and/or sub-folder(s) as appropriate.
Download the Demo Program
Download and store the following file(s) to your storage device in the appropriate folder(s). Following the methods of your compiler/IDE, compile and run the program(s). Study the source code file(s) in conjunction with other learning materials.
Download from Connexions: Demo_String_Class.cpp
- A sequenced collection of elements of the same data type with a single identifier name.
- Combining two strings into one string.
- String Class
- A complex data item that uses object oriented programming.
- Class Member
- An operator used to invoke functions associated with a class.