This paper presents overview and student functions of a programming education support tool pgtracer utilizing fill-in-the-blank questions. Pgtracer runs under Moodle and provides fill-in-the-blank questions composed of a C++ program and a trace table to the students. The tool can provide questions having various difficulty levels from the same program. This can be realized by changing the position of the blanks of the program and trace table. When a student fills the blanks, the tool automatically evaluates the answer. The tool automatically collects answers, time and evaluation result as student log. A teacher can analyze understanding level of the students by analyzing the log.