Introduction to Computer Science: Files and Data Types

1. Summary • Assignment due on Wednesday, October 29, 2003. • Tutor will be in the lab on Tuesday evening, from 7 – 9 pm. • Last time, we talked about using files. • What are the steps needed to read/write data from/to files? CS150 Introduction to Computer Science 1

2. Example • Write a program to read five integer numbers from a file, and calculate the sum. • Whenever you pass an ifstream or ofstream variable to a function, you must pass it by reference (i.e. &). • Why? CS150 Introduction to Computer Science 1

3. Ch. 7 Data Types • We’ve seen: • ints: typically 32 bits, can be 16 • floats: typically 32 bits • chars: typically 8 bits • New: • short: typically 16 bits • long: typically 64 bits • double: typically 64 bits • System dependent • Look at climit and cfloat on p. 350 CS150 Introduction to Computer Science 1

4. Characters • Characters stored in one byte • Represented by ASCII value • American Standard Code for Information Interchange • Characters are stored as an 8 bit int • Relationships • ‘0’ < ‘1’ < ‘2’ < ‘3’ < ‘4’ < ‘5’ < ‘6’ < ‘7’ < ‘8’ < ‘9’ • ‘a’ < ‘b’ < ‘c’ < ‘d’ < ‘e’ < ‘f’ < ‘g’ < ‘h’ < ‘i’ <… • ‘A’ < ‘B’ < ‘C’ < ‘D’ < ‘E’ < ‘F’ < ‘G’ < ‘H’ < ‘I’ < ‘J’ < ‘K’… CS150 Introduction to Computer Science 1

5. ASCII Values • 0 – 256 • Some ASCII values correspond to invisible characters (sounds) • The ones that are of interest to us are: ‘0’ is 48 ‘A’ is 65 ‘a’ is 97 CS150 Introduction to Computer Science 1

6. What is the Output? char ch1, ch2; ch1 = '0'; ch2 = 'C'; cout << setw(4) << ch1 << setw(4) << ch2 << endl; cout << setw(4) << (int) ch1 << setw(4) << (int) ch2 << endl; CS150 Introduction to Computer Science 1

7. What is the Output? float x,y; int i; y = 12.345; i = (int) y; x = (int) (y * 10) / 10.0; cout << setw(10) << i << setw(10) << x; CS150 Introduction to Computer Science 1

8. What is the Output? • Segment #1 int chval; for (chval = 50; chval <= 52; chval++) cout << (char) chval << endl; • Segment #2 int i; char ch; ch = 'a'; for (i = (int) ch; i <= (int) ch + 2; i++) cout << (char) i << endl; CS150 Introduction to Computer Science 1

9. Program • The printable characters have ASCII values in the range of 32 to 126. Write a C++ program segment that will print the printable character and its associated ASCII value 8 values per line. CS150 Introduction to Computer Science 1

10. Char Operations • Useful operations: islower, toupper, isdigit, islower, isspace, isupper, tolower #include <ctype> void todigit(char, &int); … void todigit(char ch, &int num) { if (isdigit(ch)) num = int(ch) - int (‘0’); } CS150 Introduction to Computer Science 1

11. Char I/O Operations • Using cin, can we read in all possible chars? • We need some other operations CS150 Introduction to Computer Science 1

12. Program #include <iostream> int main() { char ch; int count; count = 0; cin.get(ch); while (!cin.eof()) { count++; cin.get(ch); } cout << "Number of characters = " << count << endl; } CS150 Introduction to Computer Science 1

13. Program #include <iostream> int main() { char ch; cin.get(ch); while (!cin.eof()) { cout.put(ch); cin.get(ch); } } CS150 Introduction to Computer Science 1

14. Program #include <iostream> int main() { const char newline = '\n'; char ch; int count; cin.get(ch); while (!cin.eof()) { while (ch != newline && !cin.eof()) { cout.put(ch); cin.get(ch); } cout.put(newline); cin.get(ch); } } CS150 Introduction to Computer Science 1

15. Program #include <iostream> int main() { const char newline = '\n'; char ch; int count; cin.get(ch); while (ch != newline && !cin.eof()) { cout.put(ch); cin.get(ch); } cout.put(newline); } CS150 Introduction to Computer Science 1