View Compilation Error

0_0_36487387_10866.cpp: In function 'int read()':
0_0_36487387_10866.cpp:4:23: error: 'isdigit' was not declared in this scope
     while (!isdigit(ch)) {
                       ^
0_0_36487387_10866.cpp:6:22: error: 'getchar' was not declared in this scope
         ch = getchar();
                      ^
0_0_36487387_10866.cpp:8:22: error: 'isdigit' was not declared in this scope
     while (isdigit(ch)) {
                      ^
0_0_36487387_10866.cpp:10:22: error: 'getchar' was not declared in this scope
         ch = getchar();
                      ^
0_0_36487387_10866.cpp: In function 'void write(int)':
0_0_36487387_10866.cpp:19:20: error: 'putchar' was not declared in this scope
         putchar('-');
                    ^
0_0_36487387_10866.cpp:23:25: error: 'putchar' was not declared in this scope
     putchar(x % 10 + '0');
                         ^