Slides by Omer Strulovich and Ron Rubinstein

Transcription

1 Slides by Omer Strulovich and Ron Rubinstein With thanks to: Chaim Gotsman, Yechiel Kimchi, Yossi Gil, Eliezer Kantorowitz, Ayal Itzkoviz, Dani Kotlar and Itai Sharon.

2 Learn to develop large scale software Learn about object oriented programming Meet C++ Extend knowledge of C Learn to work in UNIX environment 2

3 Typically 10-1,000 lines. Typically at least 10,000 lines. Consequences Developed by an individual. Used by the programmer. Might run first time. Can be coded immediately. May have flaws Requires debugging. No standards required. Easy!! Developed by a team. Used by a customer. Never runs first time. Requires analysis/design. Must be robust. Requires long-term maintenance. Standard compliant. Difficult!! Example: A sorting program Example: Firefox 3

4 Fulfilling requirements Determining software requirements is not the subject of this course Easy to maintain: code is correct Fix bugs Add new features Not breaking old code! code is good 4

5 Simple to read No code duplication Can be tested easily Errors are found early Intuitive Efficient? Commented? 5

6 void printbeststudent(char* names[], int n, double* grades[], int gradecounts[]) { int i, j; double gradesum, bestavg, curravg; char* beststudent; if (n <= 0) return; gradesum = 0.0; for (i = 0; i < gradecounts[0]; i++) { gradesum += grades[0][i]; bestavg = gradesum / gradecounts[0]; beststudent = names[0]; for (i = 1; i < n; i++) { gradesum = 0.0; for (j = 0; j < gradecounts[i]; j++) { gradesum += grades[i][j]; curravg = gradesum / gradecounts[i]; if (curravg > bestavg) { beststudent = names[i]; bestavg = curravg; printf("the student with the highest average is %s", beststudent); 6

7 void printbeststudent(student* students[], int size) { int i, j; double gradesum = 0.0, bestavg, curravg; Student* beststudent; improving and restructuring the code, without harming its correctness if (size <= 0) return; gradesum = 0.0; for (i = 0; i < students[0]->numgrades; i++) { gradesum += students[0]->grades[i]; bestavg = gradesum / students[0]->numgrades; beststudent = students[0]; for (i = 1; i < size; i++) { gradesum = 0.0; for (j = 0; j < students[i]->numgrades; j++) { gradesum += students[i]->grades[j]; curravg = gradesum / students[i]->numgrades; if (curravg > bestavg) { beststudent = students[i]; bestavg = curravg; struct student { char* name; double* grades; int numgrades; ; typedef struct student Student; 7 printf("the student with the highest average is %s", beststudent->name);

8 void printbeststudent(student* students[], int size) { if (size <= 0) return; double gradesum = 0.0; for (int i = 0; i < students[0]->numgrades; i++) { gradesum += students[0]->grades[i]; double bestavg = gradesum / students[0]->numgrades; Student* beststudent = students[0]; declare variables only when actually needed for (int i = 1; i < size; i++) { gradesum = 0.0; for (int j = 0; j < students[i]->numgrades; j++) { gradesum += students[i]->grades[j]; double curravg = gradesum / students[i]->numgrades; if (curravg > bestavg) { beststudent = students[i]; bestavg = curravg; printf("the student with the highest average is %s", beststudent->name); 8

9 void printbeststudent(student* students[], int size) { if (size <= 0) return; double gradesum = 0.0; for (int i = 0; i < students[0]->numgrades; i++) { gradesum += students[0]->grades[i]; double bestavg = gradesum / students[0]->numgrades; Student* beststudent = students[0]; for (int i = 1; i < size; i++) { gradesum = 0.0; for (int j = 0; j < students[i]->numgrades; j++) { gradesum += students[i]->grades[j]; double curravg = gradesum / students[i]->numgrades; if (curravg > bestavg) { beststudent = students[i]; bestavg = curravg; Déjà vu printf("the student with the highest average is %s", beststudent->name); 9

10 double getstudentaverage(student* student) { double sum = 0.0; for (int i = 0; i < student->numgrades; ++i) { sum += student->grades[i]; return sum / student->numgrades; code duplication removed void printbeststudent(student* students[], int size) { if (size <= 0) return; double bestaverage = getstudentaverage(students[0]); Student* beststudent = students[0]; for (int i = 1; i < size; i++) { double currentaverage = getstudentaverage(students[i]); if (currentaverage > bestaverage) { beststudent = students[i]; bestaverage = currentaverage; printf("the student with the highest average is %s", beststudent->name); 10

11 Student* getbeststudent(student* students[], int size) { if (size <= 0) return NULL; Student* best = students[0]; for (int i = 1; i < size; i++) { if (getstudentaverage(students[i]) > getstudentaverage(best)) { best = students[i]; split code to coherent functions to make it more reusable return best; void printbeststudent(student* students[], int size) { Student* best = getbeststudent(students, size); if (best!= NULL) { printf("the student with the highest average is %s", best->name); 11

12 More C and the C99 standard Splitting code into modules Testing Object Oriented Programming Introduction to C++ Working in a UNIX environment (Tutorials) 12

13 De-facto industrial standard. Mother tongue of Unix systems. Structured language. C++ is an object-oriented syntactic extension of C. 13

14 An intuitive concept. Enables modularity and information hiding. Makes maintenance easier. 14

15 Multi-user/multi-tasking operating system. De-facto standard across multiple platforms. Powerful procedural user-interface. The UNIX System Stable. 15

16 Can run on a variety of platforms. Good programming tools (e.g. text manipulation programs). The open systems philosophy 16

17 The C Programming Language (2nd Edition, ANSI-C) B. Kernighan and D. Ritchie, Prentice-Hall, 1988 A Book on C: Programming in C (4th Edition) A. Kelley and I. Pohl, Addison-Wesley Professional, 1998 Unix in a Nutshell (4th Edition) A. Robbins, O'Reilly Media, Inc,

18 The C++ Programming Language (3rd Edition) B. Stroustrup, Addison-Wesley Longman, 1997 Effective C++: 55 Specific Ways to Improve Your Programs and Designs (3rd Edition) S. Meyers, Addison-Wesley Professional, 2005 C++ Primer (4th Edition) S. Lippman, J. Lajoie, B. Moo, Addison-Wesley Professional, 2005 Code Complete: A Practical Handbook of Software Construction 2nd edition Steve McConnell, Microsoft Press,

19 "Programs must be written for people to read, and only incidentally for machines to execute." - Abelson and Sussman 19