View Compilation Error

0_0_17929085_2145.cpp: In function 'void pre_1()':
0_0_17929085_2145.cpp:68:27: error: 'memset' was not declared in this scope
     memset(q1,0,sizeof(q1));
                           ^
0_0_17929085_2145.cpp: In function 'void work1()':
0_0_17929085_2145.cpp:133:25: error: 'memset' was not declared in this scope
     memset(q,0,sizeof(q));
                         ^
0_0_17929085_2145.cpp: In function 'int main()':
0_0_17929085_2145.cpp:172:33: error: 'memset' was not declared in this scope
         memset(num,0,sizeof(num));
                                 ^