Midterm Exam

Online, 1 hour, Wed 3/2 8:00 AM - 10:00 PM

The midterm will be taken online in Gradescope.

You will have one hour to complete the exam. To permit flexibility in your schedule, you may take the exam at any point within the block on Wednesday 3/2 from 8:00AM through 10:00PM EDT (i.e., you must start by 9:00PM in order to have the full allotment of time). Once you begin the exam, you must complete it in one contiguous 1-hour session. Gradescope will display the time remaining - when time runs out, it will end the exam. (Your answers are autosaved as you enter them, though we don't recommend answering questions until the very last second...)

Rules

This will be a mostly "open-book" exam: you may refer to the course's textbooks, your notes, and the course materials found on or linked directly from the course's website. You may refer to your own assignment solutions. You may not access other information on the Internet. You may not compile or run any code on armlab or any other machine. The exam will emphasize application of concepts and not memorization, so you will be provided with information such as manual pages, C operator precedence tables, etc. if they are necessary.

You are not allowed to communicate with any other person, whether inside or outside the class. You may not send the exam problems to anyone, nor receive them from anyone, nor communicate any information about the problems or their topics. Because students may be taking the exam late, this applies from when you take the exam until the sample solution has been published.

You will be required to type out and sign an honor code pledge that you have abided by these exam rules and restrictions.

Once the exam window begins, no questions about study material will be answered and Ed will operate in "moderation" mode, where questions must be approved by a member of the course staff. If you have technical issues or need to ask a clarifying question about the wording of some problem, please post a private message on Ed.

Topics

You will be responsible for material from the course through week 5 (but not including Monday/Tuesday of week 6), including the content of required readings, lectures, precepts, and assignments. All questions will assume the ArmLab/Linux/C/gcc217 environment unless otherwise stated.

Major topics include:

1. Number Systems
   • Binary, octal, hexadecimal number systems
   • Unsigned integers: finite representation and operations
   • Signed integers: finite two's complement representation and operations
   • Overflow
2. C Programming
   • The program preparation process: preprocess, compile, assemble, link
   • Program structure: multi-file programs using header files
   • Statements
   • Operators
   • Input/output: getchar(), fgetc(), putchar(), fputc(), gets(), fgets(), puts(), fputs(), scanf(), fscanf(), printf(), fprintf()
   • Data types
   • Variable declarations and definitions
   • Process memory layout: text, stack, heap, rodata sections
   • Constants: #define, constant variables, enumerations
   • Function declarations and definitions
   • Arrays and pointers, call by reference, arrays as parameters, strings
   • Command-line arguments
   • Structures
   • Dynamic memory management: malloc(), calloc(), realloc(), and free()
   • Common memory/pointer errors: dereference of NULL, dereference of dangling pointer, memory leak, double free
3. Programming techniques and tools
   • git and source code management
   • make and build management
   • Testing
   • gdb and debugging
   • Deterministic finite-state automata (DFA)
   • Data structures: linked lists and hash tables
   • Abstract data types
   • Modularity, separation of interface and implementation

Questions from Previous Semesters

A good way to practice for the exam is to go over questions from previous COS 217 midterm exams. Be aware that both the content of the course and the format of the midterm do change over the years, so not all questions are guaranteed to be 100% relevant, or good practice for this year. If you have any questions about whether the content of a question would be fair game for this year, please ask on Ed.

• Sample questions and answers
• Exclusions - questions on topics we haven't covered
• Topics index for the sample questions

Q&A

There will be a Q&A session on Monday 2/28 at 4:30 PM in CS 104. This will cover midterm review questions, including going over requested previous midterm problems. We will stream and record the session.

Spring Break

There will be no lectures, precepts, or office hours between Wednesday 3/2 and Sunday 3/13, inclusive. Enjoy your break!