View Compilation Error

0_0_22776019_19951.cpp: In function 'void bigNumAdd(char*, char*, char*)':
0_0_22776019_19951.cpp:6:8: error: 'MAXSIZE' was not declared in this scope
 char m[MAXSIZE] = { 0 };
        ^
0_0_22776019_19951.cpp:8:36: error: 'memset' was not declared in this scope
 memset(sum, 0, MAXSIZE*sizeof(char)); //这里不能写成memset(sum,0,sizeof(sum));原因见注意事项1  
                                    ^
0_0_22776019_19951.cpp:10:20: error: 'strlen' was not declared in this scope
 int lenA = strlen(a);
                    ^
0_0_22776019_19951.cpp:14:1: error: 'm' was not declared in this scope
 m[i] = a[lenA - i - 1] - '0';
 ^
0_0_22776019_19951.cpp:18:1: error: 'n' was not declared in this scope
 n[i] = b[lenB - i - 1] - '0';
 ^
0_0_22776019_19951.cpp:23:11: error: 'm' was not declared in this scope
 sum[i] = (m[i] + n[i] + c) % 10 + '0';//得到末位  
           ^
0_0_22776019_19951.cpp:23:18: error: 'n' was not declared in this scope
 sum[i] = (m[i] + n[i] + c) % 10 + '0';//得到末位  
                  ^