C++ Program to Read and Calculate the Sum of Five Integer Numbers from a File

1. 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

2. 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

3. 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’ CS150 Introduction to Computer Science 1

4. 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

5. Type Casting • There are two ways to perform type casting • cout << (int) ‘a’; • Cout << int(‘a’); CS150 Introduction to Computer Science 1

6. What is the Output? • int(‘d’)-int(‘a’) • char((int(‘M’) – int(‘A’)) + int(‘a’)) • int(‘7’) – int(‘0’) • char(int(‘5’) + 1) CS150 Introduction to Computer Science 1

7. 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

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

9. 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

10. 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

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