//I write a few variables declaration,then include this head-file in multiple realization-c-file,then appear "multiple definition of ‘var1 ‘ " error
resolution:
exists-file:myhead.h,realize1.c,realize2.c,main.c
add:myhead.c
1.move the defintion-entity-var at myhead.h to myhead.c
2.in the myhead.h,announce these var through "extern".
c a header file realize of multiple .c file
原文：http://www.cnblogs.com/BreaverHeart/p/6037458.html