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Thinking in C++
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Calling other programs

While the typical way to use a program that reads from standard input and writes to standard output is within a Unix shell script or DOS batch file, any program can be called from inside a C or C++ program using the Standard C system( ) function, which is declared in the header file <cstdlib>:

//: C02:CallHello.cpp
// Call another program
#include <cstdlib> // Declare "system()"
using namespace std;

int main() {
} ///:~

To use the system( ) function, you give it a character array that you would normally type at the operating system command prompt. This can also include command-line arguments, and the character array can be one that you fabricate at run time (instead of just using a static character array as shown above). The command executes and control returns to the program.

This program shows you how easy it is to use plain C library functions in C++; just include the header file and call the function. This upward compatibility from C to C++ is a big advantage if you are learning the language starting from a background in C.

Thinking in C++
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   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire