QT learning 01 GUI program principle analysis

Qt Study 01 GUI Program principle analysis

Command line application

Features of command line applications (Command Line Interface)

• It's a kind of Based on sequential execution structure Executable program of
• Program execution There is no need to interact with the user
• After the program is executed The final Running results

Example ：gcc Compiled source code

gcc a.c b.c c.c

There is no user interaction during compilation , After compilation, it either becomes an executable program or gives an error message .

The running mode of the command line application

characteristic ： The operation of the program has Fixed start and Fixed end

The command line application is suitable for

• Single task situations
• No interaction or simple interaction
• Server applications

Command line application is the main program type in the early computer system

Graphical interface applications

Features of GUI applications (Graphic User Interface)

• It's a kind of Based on the message driven model Executable program of
• Execution of procedures Depending on the user interaction process
• Program execution Real time response to user actions
• Generally, the program will not exit after execution

Running mode of GUI application

Message processing model for GUI applications

principle ： The user uses the mouse or keyboard to operate the computer , The operating system generates the corresponding system message , Send to a focused application , The application receives a system message , Call the message processing function to process the user operation accordingly .

The process ： User generated user actions => The operating system receives and generates system messages => The application receives and calls the message handler

Most of the time, the programming of graphical interface application is to write message processing functions to process system messages

The GUI application is suitable for

• multitasking The occasion of
• Strong user interaction The occasion of
• Non professional computer users

Graphical interface application program is the main program type in modern computer system

Graphical interface program VS Command line program

• Contemporary large-scale software product architecture model

Summary

Command line application	Graphical interface applications
Based on sequential execution structure	Based on the message driven model
Weak interactive execution	Strong interactive execution
Triggered by the user	Run triggered by the user
Take the initiative to end	End triggered by the user