Running a C++ Application Using GNU C++ with Linux

For this test drive, we assume that you know how to copy the examples into your home directory. Also, for the figures in this section, we use a bold highlight to point out the user input required by each step. The prompt in the shell on our system uses the tilde (~) character to represent the home directory, and each prompt ends with the dollar sign ($) character. The prompt will vary among Linux systems.

1. Locating the completed application. From a Linux shell, change to the completed GuessNumber application directory (Fig. 1.14) by typing

then pressing Enter. The command cd is used to change directories.

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Fig. 1.14. Changing to the GuessNumber application’s directory.

2. Compiling the GuessNumber application. To run an application on the GNU C++ compiler, you must first compile it by typing

as in Fig. 1.15. This command compiles the application and produces an executable file called GuessNumber.

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Fig. 1.15. Compiling the GuessNumber application using the g++ command.

3. Running the GuessNumber application. To run the executable file GuessNumber, type ./GuessNumber at the next prompt, then press Enter (Fig. 1.16).

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Fig. 1.16. Running the GuessNumber application.

4. Entering your first guess. The application displays "Please type your first guess.", then displays a question mark (?) as a prompt on the next line (Fig. 1.16). At the prompt, enter 500 (Fig. 1.17). [Note: This is the same application that we modified and test-drove for Windows, but the outputs could vary based on the compiler being used.]

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Fig. 1.17. Entering an initial guess.

5. Entering another guess. The application displays "Too high. Try again.", meaning that the value you entered is greater than the number the application chose as the correct guess (Fig. 1.17). At the next prompt, enter 250 (Fig. 1.18). This time the application displays "Too low. Try again.", because the value you entered is less than the correct guess.

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Fig. 1.18. Entering a second guess and receiving feedback.

6. Entering additional guesses. Continue to play the game (Fig. 1.19) by entering values until you guess the correct number. When you guess correctly, the application displays "Excellent! You guessed the number."

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Fig. 1.19. Entering additional guesses and guessing the correct number.

7. Playing the game again or exiting the application. After you guess the correct number, the application asks if you’d like to play another game. At the "Would you like to play again (y or n)?" prompt, entering the one character y causes the application to choose a new number and displays the message "Please type your first guess." followed by a question mark prompt (Fig. 1.20) so you can make your first guess in the new game. Entering the character n ends the application and returns you to the application’s directory in the shell (Fig. 1.21). Each time you execute this application from the beginning (i.e., Step 3), it will choose the same numbers for you to guess.

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Fig. 1.20. Playing the game again.

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Fig. 1.21. Exiting the game.