(Q) Hello world!

Question 1

* Compilation:

Test the functionality of the icons found in the left down corner in Qt Creator by modifying the program code and checking what happens when you press the icons. If your aim is to compile the written program code without executing it, which of the icons should you click?

Green triangle

Green triangle with a bug

Hammer

Question 2

* Execution:

What does the icon with green triangle do?

Compiles the program

Executes the program

Compiles and executes the program

Compiles the program if needed, and after that executes it

Executes the program only if the program is already compiled, otherwise does nothing

Question 3

* Compilation errors:

Make an error in the program code, for example, remove a semicolon. Where does Qt Creator show the compilation error messages?

In the same window as the program execution output

In window 1 Issues, below the program code

In window 3 Application output, below the program code

In window 5 Debugger Console, below the program code

Question 4

* Warnings:

Qt Creator shows a red circle before an error and a yellow triangle before a warning. What is the difference between errors and warnings?

Not much, both of them must be fixed before you can execute the program.

Errors prevent finishing compilation, but warnings do not. In other words, you can execute the program, although there are warnings.

Warnings prevent finishing compilation, but errors do not. In other words, you can execute the program, although there are errors.

Warnings are useless, and it is better to make them invisible by clicking ”Show warnings” button at the top of Issues window.

Question 5

* Removing warnings:

In Hello world program created by Qt Creator, main function has two cryptic parameters. They produce warnings, because the program does not use them. (We will consider these parameters only in the end part of the course - they are related to executing a C++ program from the command line - and thus, they will be useless for many rounds.) What is the most reasonable way to get rid of the warnings concerning useless parameters?

Writing some ”vain” use for such parameters (e.g. argc = 0;)

Removing the parameters from the function definition, i.e. the definition will be just int main()

Warnings are useless, and it is better to make them invisible by clicking ”Show warnings” button at the top of Issues window

Question 6

* Program crash:

After the printing line, add the following line:

cout << "Division by zero: " << 1/0 << endl;

Division by zero produces a warning in compiling, and, of course, the program crahes when executing it. How can you see in Qt Creator that the program crashed?

There is a run-time warning message in the same window as the program execution output

In window 1 Issues, below the program code; if look carefully, you can also see the window flashing in a diffent colour

In window 3 Application output, below the program code; if look carefully, you can also see the window flashing in a diffent colour

In window 4 Compile output, below the program code; if look carefully, you can also see the window flashing in a diffent colour

Question 7

* Running and closing debugger:

As you can concluded by the previous point, Qt Creator does not emphasize that the program crashed. It is easier to detect program crash, if you execute the program in debug mode. This can be done by clicking the green triangle with a bug. Debugger informs about the crash in a pop-up window and shows the line number, where the execution ended. When using debugger in Qt Creator, it is very important to note:

Turn the debugger off by clicking the red square with a bug. Otherwise it continues execution and makes Qt Creator slow, especially if you have several debuggers executing.
Move from debug mode back to edit mode by clicking the black menu on the left side.

If you forget to turn debugger off, but move to edit mode, how can you see from edit mode that the debugger is still on?

Based on the starting icon of the debugger

Based on the message in window 1 Issues

By executing the program again using run button

Question 8

* Opening and closing files in a project:

Close file main.cpp (or main.cc), for example, by pressing X in the dark top bar of the edit window. How can you open the file just closed?

From Projects window, selecting Open Documents tab

By navigating in Projects tab to Sources folder and double-clicking file main.cpp

By selecting the right file from Open Documents window

(Q) Hello world!¶