relloc explaination

the prototype of relloc is extern void *realloc(void *men_address, unsigned int newsize)

grammar
pointer name = (data type*)realloc(the name of the pointer which point to the memory that need to be changed, the new size)
the new size maybe smaller or bigger than the old size(if the new size is larger than the original memory size, the new allocation part will not be initialized; if the new size is smaller than tne original memory size, it maybe cause data loss[1-2])
语法
指针名=（数据类型*）realloc（要改变内存大小的指针名，新的大小）。
新的大小可大可小（如果新的大小大于原内存大小，则新分配部分不会被初始化；如果新的大小小于原内存大小，可能会导致数据丢失[1-2] ）

returns a pointer to the allocated memory if the reassignment is successful, otherwise return NULL pointer;

如果重新分配成功则返回指向被分配内存的指针，否则返回空指针NULL