View Compilation Error

0_0_34792363_12602.cpp: In function 'int main()':
0_0_34792363_12602.cpp:5:12: error: 'prim' was not declared in this scope
     memset(prim,0,sizeof(prim));//初始化prim数组，默认所有数都是素数
            ^
0_0_34792363_12602.cpp:5:31: error: 'memset' was not declared in this scope
     memset(prim,0,sizeof(prim));//初始化prim数组，默认所有数都是素数
                               ^