Chapter 14 Stream Input and Output

By C. Shing

ITEC Dept

Radford University

Slide 2

Objectives Understand how to use unformatted input (cin)

and output (cout) Understand how to use formatted input (cin)

and output (cout)

Slide 3

Inheritance Chart iostream class ios

istream ostream

iostream

Slide 4

Unformatted Input Use stream extraction (>>)

Input a character

char c;

cin >> c; Input a string

char string[SIZE];

cin >> string;

Slide 5

Unformatted Input (Cont.)

Example 1

Slide 6

Unformatted Input (Cont.) Use cin member function

Input a characterchar c=cin.get();

Input a linechar line[80];

cin.getline(line, 80); Input a string

char string[SIZE];cin.get(string, SIZE); or cin.read(string, SIZE);

Slide 7

Unformatted Input (Cont.)Other related cin member functions:

1. cin.eof(): returns 0 if not reach EOF. Returns 1 otherwise.

2. cin.ignore(n, c): ignore n characters until the character c

3. cin.putback(c): put the character c back to reading stream

4. cin.peek(): peek the next charcter in the reading stream

5. cin.gcount(): return # of characters last read

Slide 8

Unformatted Input (Cont.)

Example 2

Example 3

Slide 9

Unformatted Output Use stream insertion (<<)

Ouput a character

char c;

cout << c; Output a string

char string[SIZE];

cout << string;

Slide 10

Unformatted Output (Cont.) Use stream insertion (<<) (Cont.)

Ouput string address (by casting to type void *)

char string[SIZE];

cout << “string address is “

<< static_cast<void *>string; Ouput variable address

cout << “number address is “

<< &number;

Slide 11

Unformatted Output (Cont.) Use cout member function

Output a character

char c=cout.put(); Output 2 characters

char c1, c2

cout.put(c1).put(c2); Output a string

char string[SIZE];

cout.write(string, SIZE); or

cout.write(string, cin.gcount());

Slide 12

Unformatted Output (Cont.)

Example 4

Slide 13

Formatted Input/Output Include stream manipulator:

#include <iomanip> Can use either parametrized stream manipulator

or member functions

Slide 14

Formatted Input

Manipulator Member function

Explain

setw(n) cin.width(n) use n characters to read

Slide 15

Formatted Input (Cont.)

Example 5

Example 6

Slide 16

Formatted Output

Manipulator Member function Explain

setbase(n)/dec/oct/hex

n=10(decimal),8(octal),16(hexadecimal)

setw(n) cout.width(n) n-1 characters to read

setprecision(n) cout.precision(n) n places after decimal point

setfill(c) cout.fill(c) Pad blank with character c

Slide 17

Formatted Output (Cont.)

Manipulator Member function Explain

setiosflags(flag)/setf(flag),resetiosflags(flag)/unsetf(flag)

cout.setf(flag), cout.unsetf(flag)

Set, reset stream format state

flags(flag)/flags() cout.flags(flag)/cout.flag()

Set format flag and return the previous format/show current format flag

Slide 18

ios Class Flags

Format state flag Explain

ios::skipws Skip white space on input stream

ios::left/ios::right Left/right justified

ios::internal Left justify sign, right justify number

ios::showbase Specify base

Slide 19

ios Class Flags (Cont.)

Format state flag Explain

ios::dec/ios::oct/ios::hex

Show values in base 10/8/16

ios::showpoint Show decimal point

ios::showpos Show signs

ios::scientific Show scientific notation

Slide 20

ios Class Flags (Cont.)

Format state flag Explain

ios::uppercase Show uppercase for letters of output

ios::fixed Show fixed floating point

ios::showpos Show signs

ios::scientific Show scientific notation

Slide 21

Formatted Output (Cont.)

Base Conversion

Slide 22

References Deitel & Deitel: C How to Program, 4th ed.,

Chapter 21, Prentice Hall