View Compilation Error

0_0_31764189_29547.cpp: In function 'int main()':
0_0_31764189_29547.cpp:6:23: error: 'scanf' was not declared in this scope
    while(scanf("%s",&a)!=EOF)
                       ^
0_0_31764189_29547.cpp:6:26: error: 'EOF' was not declared in this scope
    while(scanf("%s",&a)!=EOF)
                          ^
0_0_31764189_29547.cpp:18:28: error: 'printf' was not declared in this scope
            printf("%c",a[i]);
                            ^
0_0_31764189_29547.cpp:22:19: error: 'printf' was not declared in this scope
        printf("\n");
                   ^