Exam 2.1 and 2.2 (CMSC216 Spring 2020)

General Information

Date (Exam 2.1): Thursday April 16
- Time:
  - 11:40 am - 12:15 pm (for 010x and 030x sections)
  - 12:30 pm - 1:05 pm (for 020x sections)
- Duration: 35 minutes
Date (Exam 2.2): Tuesday April 21
- Time (limited to 70 mins):
  - 11:00 am - 12:15 pm (for 010x and 030x sections)
  - 12:30 pm - 1:45 pm (for 020x sections)

Additional details (e.g., Zoom meeting links) will be announced in Piazza
Open-book, open-notes
But, you are NOT allowed to use Internet (e.g., search), to access grace, or to run code locally. These are academic integrity violations.
The best way to prepare for the exam is to practice old exams. Complete several of them in the allocated time specified in the exam.
After you have taken the exam, do not discuss anything associated with the exam with other students that might not have taken the exam yet.
Posting any information in Piazza about the exam after taking it is considered an academic integrity violation.

Exam Structure

Short answer questions: This includes for example, multiple choice, true/false, and fill-in-the-blank type questions.
Code analysis questions: We will give a short segment of code and you may be asked to identify syntax and logical errors, generate code output, etc.
Code Writing: Write a program/code snippets to solve a given problem. You should be prepared to give a complete program, but we may also ask you to provide just a single function or a code fragment.

Topics

The exam will include all the material covered in discussion session (lab), lecture, quizzes, exercises, and projects including the following topics:

Unix - You must be familiar with the following commands.
- cp
- ls
- cd
- pwd
- gcc
- rm
- mv
- diff
- rmdir
- rm -r
- How to use grep to find patterns in a file
- How to change file / directory permissions (e.g., chmod 700 file)
C Language
- Preprocessor directives (e.g., #include, #define, #ifdef)
- Expressions
- Bitwise Operators. Some sample questions can be found at BitwiseOpWorksheet.pdf.
- Conditional statements
- Loops
- Arrays (one and two dimensional arrays)
- Strings - You are responsible for the following string functions.
  - strlen
  - strcpy
  - strcmp
  - strcat
  - memcpy
  - memmove
- Pointers (including function pointers)
- enum
- Structures
- Unions
- Functions
- stdin, stderr, stdout
- Linkage
- Command line arguments
- exit
- err
- perror
- Dynamic Memory Allocation (malloc, realloc, free, etc.) (not for Exam 2.1)
Data Representation, including:
- How characters, integers (positive and negative) and floats are represented.
- The 2's complement representation of a number (representation of signed integers).
- Understand the imprecision associated with real numbers.
- Why casting a variable is not the same as getting its address, casting to a type and dereferencing. The casting.c example in Data-Rep-Code provides an example.
- No need to know how to generate the binary representation for a float value using the IEEE 754 standard; just understand that some bits represent the mantissa, some bits the exponent and the left most bit the sign.
- Big Endian vs Little Endian.
Reading and writing from files.
Memory maps - Please use the style provided in the following example MemoryMapExample.pdf. Previous exam solutions consider as correct using a pointer to the first array element in order to describe an array; that is not correct. See the diagram we have provided.
Linked Lists (both singly and doubly linked lists) (not for Exam 2.1)
Recursion
Makefiles - You need to know how to define makefiles without using implicit rules. The following is an example of the kind of makefile we expect you to write in the exam: makefile_example. You may not use wildcards (except *).

The exam will NOT cover the following topics:

Assembly, fork, exec*, dup2, pipes, emacs, arduino, debugger, splint, valgrind, -fmudflapth -lmudflap

Suggestions

                    Instead of

                    if (ptr != NULL) {
                    }

                    use

                    if (ptr) {
                    }

                    When you have nested structures defining a pointer to a field can help.

                    /* Using a pointer to simplify handling structure fields */
                    printf("Section number is %d\n", all_courses[1].section1.section_number);
                    printf("Section number is %d\n", all_courses[1].section1.num_students);

                    /* Equivalent to previous two statements */
                    ptr = &all_courses[1].section1;
                    printf("Section number is %d\n", ptr->section_number);
                    printf("Number of students %d\n", ptr->num_students);

                    Instead of

                    if (strcmp(a, b) == 0) {
                    }

                    use

                    if (!strcmp(a, b)) {
                    }

                    Instead of

                    while (*p != '\0') {
                    }

                    use

                    while (*p) {
                    }

Regarding linked lists

You should try all possible combinations of additions and removal operations over a singly-linked list.
Any recursive solution for a linked list usually requires an auxiliary function. Practice recursive problems dealing with linked lists.

A significant number of non-recursive tasks can be completed with one of the following loops:

                        Node *curr = head;
                        while (curr) {
                            /* task here */

                            curr = curr->next;
                        }


                        Node *prev = NULL, *curr = head;
                        while (curr) {
                            /* task here */

                            prev = curr;
                            curr = curr->next;
                        }

Practice Material

Practice material is available in Grace under 216public/exams/exam2; ignore the parts outside the topics of this exam (eg, assembly, process control). To transfer this material to your computer, use https://dav.terpconnect.umd.edu. Use your directory id/passwd (same one used for grace) to log on.