函数的直接声明发

3_lesson/02_fun_declare/.gitignore

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+# This file is used to ignore files which are generated
+# ----------------------------------------------------------------------------
+
+*~
+*.autosave
+*.a
+*.core
+*.moc
+*.o
+*.obj
+*.orig
+*.rej
+*.so
+*.so.*
+*_pch.h.cpp
+*_resource.rc
+*.qm
+.#*
+*.*#
+core
+!core/
+tags
+.DS_Store
+.directory
+*.debug
+Makefile*
+*.prl
+*.app
+moc_*.cpp
+ui_*.h
+qrc_*.cpp
+Thumbs.db
+*.res
+*.rc
+/.qmake.cache
+/.qmake.stash
+
+# qtcreator generated files
+*.pro.user*
+
+# xemacs temporary files
+*.flc
+
+# Vim temporary files
+.*.swp
+
+# Visual Studio generated files
+*.ib_pdb_index
+*.idb
+*.ilk
+*.pdb
+*.sln
+*.suo
+*.vcproj
+*vcproj.*.*.user
+*.ncb
+*.sdf
+*.opensdf
+*.vcxproj
+*vcxproj.*
+
+# MinGW generated files
+*.Debug
+*.Release
+
+# Python byte code
+*.pyc
+
+# Binaries
+# --------
+*.dll
+*.exe
+

3_lesson/02_fun_declare/02_fun_declare.pro

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+TEMPLATE = app
+CONFIG += console
+CONFIG -= app_bundle
+CONFIG -= qt
+
+SOURCES += main.c

3_lesson/02_fun_declare/main.c

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+#include <stdio.h>
+
+// 函数的声明，一般当子函数在主函数的下方时，需要在主函数的上方进行声明
+void myfun1();
+void myfun2(int a, int b);
+int myfun3(int a, int b);
+
+int main(int argc, char *argv[])
+{
+    myfun1();
+
+    return 0;
+}
+
+// 定义一个没有参数也没有返回值的函数
+void myfun1()
+{
+    printf("hello world\n");
+    printf("nihao beijing\n");
+    printf("welcome to 1000phone\n");
+
+    return;
+}
+
+// 定义一个有参数的函数
+void myfun2(int a, int b)
+{
+    int sum;
+    sum = a + b;
+
+    printf("%d + %d = %d\n", a, b, sum);
+}
+
+// 定义一个有返回值的函数
+int myfun3(int a, int b)
+{
+    int sum;
+    sum = a + b;
+
+    return sum;
+}