ugradtas.txt

书名:C语言科学与艺术,以前交钱下载的

science, and feminist studies.  More than a quarter of the section
leaders are women, which is larger than the fraction of women in the
major.  Providing role models for a wide variety of students helps make
the CS106 course more accessible, and we work hard to maintain diversity
in the program.

5. SUPPORT STRUCTURE

Although the section-leader program has been extremely successful at
Stanford, much of that success is due to the support structure that has
grown up around the program.  Undergraduates often lack the depth of
experience that a graduate student might bring to a TA position; they
therefore need training, assistance, and administrative support to be
optimally effective in their role as members of the teaching staff.

The CS198 course

The most important aspect of the support structure for the section-
leader program is the CS198 course -- Teaching of Computer Science.  In
their first quarter with the program, section leaders enroll in CS198,
which is designed to prepare them to be more effective teachers.  New
section leaders receive university credit for CS198 but are not paid
during their first quarter of work.  Thereafter, section leaders are
paid on an hourly basis, which usually works out to 10-15 hours a week.

Because new section leaders must begin teaching section in the second
week of the quarter, CS198 is designed to cover as much information as
early in the term as possible.  The course is presented in a workshop
rather than a lecture format and meets twice  a week at the beginning of
quarter, once a week in the middle, and not at all towards the end.
There are approximately ten workshops in all, including "Grading,"
"Debugging," "Teaching Styles," "Creativity in Teaching," and "How to
Present Material."

The workshop format allows the new section leaders to develop not only
as individuals, but also as a group.  Since we do not believe that a
single formula exists for teaching, the workshops allow new section
leaders to explore their own ideas and discuss them with their peers.
In the process, they learn as much, if not more, from the other section
leaders as they do from the workshop leaders.

In addition, the workshops allow new section leaders to get to know one
another and establish connections and friendships with other section
leaders.  Each new section leader is paired with an older, more
experienced one as part of a "buddy system" that helps integrate new
people into the program.

The CS198 coordinators

Like any organization with a staff of 50, the section-leader program
requires administrative coordination.  At Stanford, that responsibility
rests with two graduate students, both former section leaders, who are
hired to serve as coordinators for the program.  Because a large part of
the job consists of running the CS198 class, these people are usually
called the "CS198 coordinators"; their charge, however, is actually much
broader and includes the following tasks:

   o  Managing the administrative mechanics of the program.  The
      coordinators are responsible for determining how many sections
      are needed, scheduling classrooms, assigning section leaders
      to specific courses and times, and distributing students among
      the individual sections.  The coordinators also identify and
      resolve problems as they arise.

   o  Hiring new section leaders.  Each quarter, the coordinators
      solicit applications from undergraduates who want to become
      section leaders.  Competition for these positions is stiff; in
      a typical quarter, only one candidate out of four is selected.
      The selection is based on two principal criteria: thorough
      knowledge of the relevant course material and teaching
      effectiveness.  The coordinators assess teaching effectiveness
      largely on the basis of an interview in which the candidate
      gives a short presentation on one of the topics likely to come
      up in section.

   o  Conducting the CS198 course.  As discussed in the preceding
      section, every new section leader takes CS198.  The
      coordinators are responsible for planning the curriculum and
      leading the workshops.

   o  Offering supplementary workshops on essential topics.  The
      coordinators conduct occasional review sessions on topics that
      are likely to cause confusion, such as strings, memory
      allocation, and abstract data types.  These workshops are open
      to all section leaders and provide continuing education for
      experienced section leaders, who are not enrolled in CS198.
      These workshops have proven valuable in easing the transition
      caused by the change in programming language, because they
      show section leaders who were introduced to certain concepts
      in Pascal how to teach those same concepts in C.

   o  Running weekly staff meetings.  The staff members for all
      three CS106 courses meet together once a week during the term,
      so that lecturers can review what's going on in each class and
      what questions to expect from students in connection with the
      current assignment.  Section leaders need to keep track of the
      assignments for all three classes so that they can respond
      effectively to the questions they get from students in the
      computer cluster.

   o  Fostering communication.  The success of the section-leading
      program depends on good communication.  Just as students
      depend on section leaders for help and information, the entire
      course staff relies on the coordinators to provide a network
      that links together the various individuals associated with
      the program.

The coordinators report to the Associate Chair for Education and
interact with the entire staff of lecturers.  Particularly as the
program has matured, however, the coordinators maintain a significant
level of autonomy, which allows the program to run smoothly most of the
time without intensive faculty supervision.

Grading systems

Many section leaders find grading to be the most difficult and
problematic aspect of their job.  While grading is never easy,
undergraduate section leaders face a special challenge for the following
reasons:

   o  Section leaders do not have the experience of a faculty member
      or a graduate TA.  Although they understand the course
      material well, they may be uncertain about how to evaluate a
      student who chooses an unconventional approach.

   o  Grading can establish an adversarial dynamic between the
      section leader and the student, which sometimes makes it
      harder to establish the individual connection that makes the
      section-leading program so successful.

   o  Because they are much closer to the student in age and
      academic status, section leaders sometimes have problems with
      students who want to argue about their grades.  A faculty
      member quickly learns how to handle the student who insists
      that a B+ should really have been an A-; a section leader has
      less experience and less authority to resist that pressure.

To make it easier for section leaders to evaluate student work without
jeopardizing their relationship with the class, we have developed a
grading system for CS106 that has the following characteristics:

  1.  The course staff develops detailed grading criteria for each
      assignment.  Before each assignment is evaluated, the
      lecturer, TA, and section leaders work together to prepare a
      comprehensive set of guidelines for grading the assignment.
      After looking at a sample of the submitted assignments, the
      members of the staff discuss what they are looking for in
      terms of a solution, what alternative strategies might be
      possible, and how much weight should be assigned to errors of
      various types.  Section leaders can then refer to the grading
      criteria as they read and evaluate the assignments.

  2.  Grading is interactive.  When a student turns in a program,
      the section leader looks it over, writes comments on the
      paper, and assigns a preliminary grade based on the specific
      grading criteria established by the staff as a whole.  The
      section leader then schedules an appointment with the student
      in which they talk about the program, running it on a computer
      if it helps to illustrate specific points about the coding.
      This dialogue turns out to be invaluable.  The student
      receives verbal feedback that is far more helpful than the
      written comments but also has a chance to explain to the
      section leader the strategy behind a particular solution.
      This discussion helps the section leader evaluate how well the
      student understands the critical concepts.

  3.  Grades are assigned on a qualitative scale that is extremely
      coarse.  After discussing all the positive and negative
      aspects of the assignment with the student, the section leader
      assigns the paper to one of several categories set by the
      lecturer.  Although the grading systems used by different
      instructors vary to some extent, one of the common approaches
      is to assign grades from the following set:

      ++      This grade must be authorized by the instructor and is
              reserved for the absolutely wonderful assignment that
              appears at most only once or twice a quarter --  the
              sort of program that "makes you weep" when you see it.

      +       This grade is used for programs that exceed the
              expectations of the course.  Assignments that merit a
              + must incorporate extra features beyond the minimal
              requirements or get the job done in a particularly
              elegant way.

      check+  This grade designates a submission that satisfies all
              the assigned requirements -- a job well done.

      check   This grade indicates that the program meets the
              general requirements for the assignment, possibly with
              a few minor problems.

      check-  This grade signifies that the program has problems
              serious enough to fall short of the assigned
              requirements.

      -       Programs that receive a - grade have extremely serious
              problems but nonetheless demonstrate some effort and
              understanding.

      --      This grade is used for programs that show little
              effort and do not represent passing work.

      Because almost all the grades are check+, check, or check-,
      the psychological importance of grading is reduced, which
      makes it possible for students to concentrate more on the
      feedback they receive during the interactive grading session.

The section-leader community

Because interpersonal ties are always an important part of any support
structure, the section-leader program tries to promote a community
atmosphere that is open and inclusive.  The coordinators are continually
involved in sponsoring an environment in which section leaders can get
to know the TAs, the lecturers, and each other.  Section leaders get
together for such activities as barbecues, basketball, four-square, and
laser tag.  By encouraging communication and interaction among section
leaders, these informal activities contribute as much to the quality of
the program as do the meetings and workshops.

The section leaders also play an important role that is not listed as
part of any job description: to serve as public representatives of the
computer science teaching community.  Section leaders are recognized
throughout the campus as people who understand computer science and
programming.  It is not unusual for a section leader to wander into a
dormitory-based computer cluster and help four or five people with their
programs.  They occasionally meet students for lunch to go over problems
with a particular assignment.  Most section leaders have had discussions
with students about the pros and cons of the computer science major or
what courses would be most valuable for them to take.  This informal
presence has had a significant impact on the undergraduate population,
to the point that new computer science majors often have a good idea of
what the department is like before they actually declare their major.

6.  CONCLUSIONS

In our experience, using undergraduates as part of the teaching process
has proven to be an extremely effective way to provide teaching support
for introductory computer science classes.  The system not only benefits
students in the class but also has a profoundly positive effect on the
section leaders involved in the program and the computer science
community as a whole.

REFERENCES

[Austing79]  Richard Austing, Bruce Barnes, Della Bonnette, Gerald
Engel, and Gordon Stokes, "Curriculum '78: Recommendations for the
undergraduate program in computer science," Communications of the ACM,
March 1979.

[Reges88]  Stuart Reges, John McGrory, and Jeff Smith, "The effective
use of undergraduates to staff large introductory CS courses," SIGCSE
Bulletin, February 1988.

[Roberts93]  Eric S. Roberts, "Using C in CS1: Evaluating the Stanford
experience," SIGCSE Bulletin, March 1993.

FOOTNOTES

[1] Although the material is largely review for many advanced students
in CS106X, we encourage even highly advanced students to begin their
computer science study at the CS106X level.  Most students -- even those
with years of programming experience in high school -- have weak
software engineering skills, which improve considerably when they take
this course.

[2] Until five years ago, CS105 also used undergraduate section leaders
to provide course assistance.  Since that time, however, CS105 and CS106
have used different programming languages, which makes it difficult to
support both courses with a single unified program.