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A large program should be organized as several interrelated segments, arranged in a logical order: The segments are called modules. A program which consists of such modules is called a modular program.
In C++, modules can be classes or functions.
We can think of a function as a program segment that transforms the data it receives into a finished result.
Each function must have a name. Names or identifiers in C++ can made up of any combination of letters, digits, or underscores selected according to the following rules:
Examples:
DegToRadintersectaddNums
FindMax1_densityslope
Examples of invalid identifiers:
1AB3
E%6
while
Note: C++ is a case-sensitive language (i.e. upper and lower case characters are treated as different letters).
The main() function is a special function that runs automatically when a program first executes.
All C++ programs must include one main() function. All other functions in a C++ program are executed from the main() function.
The first line of the function, in this case int main() is called a function header line.
The function header line contains three pieces of information:
int main()
{
program statements in here
return 0;
}
Note: The line
return 0;
is included at the end of every main function. C++ keyword return is one of several means we will use to exit a function. When the return statement is used at the end of main as shown here, the value 0 indicates that the program has terminates successfully.
The cout object is an output object that sends data given to it to the standard output display device.
To send a message to the cout object, you use the following pattern:
cout<<“text”;
The insertion operator,<<, is used for sending text to an output device.
The text portion of the statement is called a text string. Text string is text that is contained within double quotation marks.
Consider the following program.
Example
#include<iostream.h>
int main()
{
cout<<"Hello world!”;
return 0;
}
The output of the above program:
Hello world!
Before you can use any runtime libraries in your program, you must first add a header-file into your program, using the #include statement. A header file is a file with an extension of .h that is included as part of a program and notifies the compiler that a program uses run-time libraries.
One set of classes you will use extensively in the next few chapters is the iostream classes. The iostream classes are used for giving C++ programs input capabilities and output capabilities.
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