填空题 描述下列程序的功能 #include <stdio.h> int main( ) { int c[26], i; char ch; while (ch = getchar( ) != '\n') if (ch >= 'a' && ch <= 'z') c[ch - 'a']++; for (i = 0; i < 26; i++) printf("%c:%d\n", i + 'a', c[i]); return 0; }