View Compilation Error

0_0_11177725_22900.cpp: In function `int sum(int)':
0_0_11177725_22900.cpp:22: error: `a' undeclared (first use this function)
0_0_11177725_22900.cpp:22: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_11177725_22900.cpp: In function `int main()':
0_0_11177725_22900.cpp:35: error: invalid conversion from `int' to `void*'
0_0_11177725_22900.cpp:35: error:   initializing argument 1 of `void* memset(void*, int, size_t)'