Functional Decomposition and Unit Testing Essentials for Effective Coding

1. Recitation February 27, 2014

2. Test on Monday!! • Email me BEFORE the weekend if you have questions. • Project 2 will be going out next Wednesday. • We’ll review it in class next week. Announcements

3. Grades are posted using secret numbers • Grading was based on: • Writing all 3 functions • Correctly using the variables specified in function headers • Declaring necessary local variables • Correctly copying code segments Quizzes

4. Reasons for functional decomposition: • Divide and conquer! • Easier to debug since the individual pieces can be tested. • Goals when decomposing: • Enable code reuse • Hierarchical decomposition- put functions in functions Functional Decomposition

5. Pre-declaration of a function: • Takes place in a header file or above “main” • Ex. intfunction_name(int,int); • Calling the function inside of another function: • Omit the variable types and insert the variable to be passed in. • Ex. a=function_name(b,c); • Writing a function: • Can be written in a separate file or underneath main. • Include return and input variable types and names. • Ex. intfunction_name(int first, int second) { //Function code return 0; } Functional Decomposition

6. Quiz 1 Solution

7. Compiling multiple modules: • The files should be linked by a common header • Ex. #include “backgammon.h” • Recommendation: don’t #include other .c files! It makes compiling problematic. • Ex. gccbackgammon.hbackgammon.ccheck.c Compiling tricks

8. Debugging: • Use gcc –g file_name.c • Making a binary: • Use gcc –c file_name.c • Compiling and renaming: • Use gcc –o new_file_name.outold_file_name.c Compiling Tricks

9. Program Input Expected Compare Actual Test Vectors

10. Create test vectors that test one aspect or the code’s full functionality. • Use “diff” to compare the actual output to the expected output: • Ex: gccprogram.outprogram.c program.out < test1.in > test.out diff test.out test1.expected.out program.out < test2.in > ! test.out diff test.out test2.expected.out Test Vectors

11. Driver function Single function Input Expected Compare Actual Unit Tests

12. Benefits of unit test vectors: • Supports functional decomposition • Allows for incremental test and build • In theory, they can be exhaustive. Unit Tests

13. Initializing Arrays: • Arrays can be fully initialized once in C (this needs to happen when the array is first declared) • Example • Both pointers an arrays are used to access memory spaces. • The name of an array is a pointer to the first memory space occupied by the array. • Major difference: the address a pointer references can be changed. Pointers vs. Arrays

14. Initializing: int number, *pointer, **point_2_pointer; • Assigning values: number=5; pointer=&number; point_2_pointer=&pointer; printf(“%i”,**point_2_pointer); printf(“%p”,*point_2_pointer); Brief Pointer review

15. Math operations with pointers are all based on the size of the variable the pointer is used for. • Example Pointer Arithmetic

16. Creating a function with a pointer as an input: intpointer_processing(intstep,char *array, int *value) { //Function’s code return 0;} • Creating a function with a pointer as an output: char* pointer_sending(int step, char *array, int *value) { char *array_point; //Function’s code return array_point; } Pointers with functions

17. Know conversion to and from binary, octal and hexadecimal • Understand the benefits and principles of functional decomposition • Know the differences between pointers and arrays • Practice writing large pieces of code on paper under a time constraint. Tips