4. Input and Output

Question 1

I/O

Answer 1

sequence of bytes (stream of bytes) from source to destination

Question 2

stream

Answer 2

sequence of characters from source to destination

Question 3

input stream

Answer 3

sequence of characters from input device to computer

Question 4

output stream

Answer 4

sequence of characters from computer to output device

Question 5

standard I/O devices

Answer 5

use iostream to extract data from keyboard + send output to screen

Question 6

iostream contains definitions of 2 types:

Answer 6

istream - input stream

ostream - output stream

Question 7

iostream’s 2 variables

Answer 7

cin - stands for common input

cout - stands for common output

Question 8

using cin and cout

Answer 8

-include iostream must be used (preprocessor directive)
-declaration is similar to these statements:
istream cin;
ostream cout;

Question 9

extraction operator&raquo_space;

left hand operand

Answer 9

an input stream variable such as cin

Question 10

extraction operator&raquo_space;

right hand operand

Answer 10

a variable of simple data type

Question 11

extraction operator&raquo_space;

syntax using it with cin

Answer 11

cin&raquo_space; variable&raquo_space; variable …;

Question 12

use of&raquo_space;

Answer 12

every occurence of&raquo_space; extracts the next data item from the input stream

eg. cin&raquo_space; x&raquo_space; y; is equivalent to cin&raquo_space; x; cin&raquo_space; y;

skips all the whitespace

Question 13

whitespace characters

Answer 13

consist of blanks and certain nonprintable characters

Question 14

data type of input

Answer 14

eg.&raquo_space; distinguishes between character 2 and number 2 by the right hand operand of&raquo_space;

(if it is char, 2 is treated as character 2, if it is int, it is treated as number 2)

Question 15

reading data: reading into char variable

Answer 15

• eo&raquo_space; skips leading whitespace, finds + stores only next character
• reading stops after a single character

Question 16

reading data: reading into int/double variable

Answer 16

• skips leading whitespace, reads + or - (if any), reads digits (incl decimal)
• stops on whitespace non-digit character

Question 17

cin&raquo_space; z

z is adouble and 39 is input. What is the value of z?

Answer 17

z = 39.0

Question 18

functions

Answer 18

• (subprogram)
• set of instructions
• when activated, it accomplishes a task

Question 19

main function

Answer 19

executes when a program is run

other functions only execute when called

Question 20

header files

Answer 20

predefined functions organised as a collection of libraries called header files

a header file can contain several functions

Question 21

predefined functions

Answer 21

to use, need name of appropriate header file

Question 22

what you need to know to use predefined functions

Answer 22

function name
no. of parameters req
type of each parameter
what function is going to do

Question 23

predefined function example

Answer 23

-compute x using pow (power) function
-pow is in cmath library
pow takes 2 numeric parameters
-then returns a number

Question 24

cin vs get function

Answer 24

> > cant read blanks or notice new lines and skips blanks + new lines

Question 25

get function

Answer 25

• inputs next character (incl whitespace)

- stores character at location indicated by its arguments

Question 26

sytax of cin and get function

Answer 26

cin.get(varChar);

eg.
cin.get(ch1);
cin.get(ch2);
cin&raquo_space; num;
If I type “A 34”
ch1 = “A”
ch2 = “ “
num = 34

Question 27

other istream functions

Answer 27

cin.ignore(intExp, chExp);

istreamVar.clear();

istreamVar.putback(ch);

istreamVar.peek();

Question 28

cin.ignore example: cin.ignore(100, ‘.’);

Answer 28

-ignore next 100 characters or ignore input until it encounters ‘.’. Whichever comes first. The ‘.’ will be discarded too.

Question 29

input failure

Answer 29

• input data does not match corresponding variables
• input stream enters fail state
• all further I/O statement using that stream ignored
• program continues to execute w/ values stored in variables
• causes incorrect results

Question 30

syntax of cout and <

Answer 30

cout &laquo_space;expression or manipulator &laquo_space;expression or manipulator &laquo_space;…;

called output statement

Question 31

&laquo_space;oeprator

Answer 31

called insertion operator or stream insertion operator

Question 32

manipulator

Answer 32

alters output

Question 33

endl

Answer 33

simplest manipulator, causes cursor to move to beginning of next line

Question 34

\n

Answer 34

newline

cursor moves to beginning of next line

Question 35

\t

Answer 35

tab

moves to next tab stop

Question 36

\b

Answer 36

backspace

moves 1 space to left

Question 37

\r

Answer 37

return

moves to beginning of current line

Question 38

\

Answer 38

backslash

blackslash is printed

Question 39

'

Answer 39

single quotation

single quotation mark printed

Question 40

"

Answer 40

double quotation

double quotation mark printed

Question 41

formatting output commands

Answer 41

setprecision(n)
fixed
showpoint
setw

Question 42

setprecision(n)

Answer 42

outputs decimal numbers up to n decimal places

Question 43

fixed

Answer 43

outputs floating-point numbers in a fixed decimal format

Question 44

showpoint

Answer 44

forces output to show decimal point + trailing zeros

Question 45

eg of setprecision and fixed

Answer 45

cout &laquo_space;setprecision(5) &laquo_space;f;
= 3.1416

cout &laquo_space;fixed &laquo_space;setprecision(5) &laquo_space;f;
3.14159

Question 46

setw

Answer 46

outputs value of an expression in specific columns

Question 47

types of manipulators

Answer 47

with parameters and without parameters

Question 48

parameterised

Answer 48

req iomanip header

eg. setprecision, setw, setfill

Question 49

nonparameterised

Answer 49

req iostream header

eg. endl, fixed, showpoint, left, flush

Question 50

I/O and string type

Answer 50

eo&raquo_space; skips leading whitespace chars and reading stops at a whitespace character

Question 51

reading strings with blanks

Answer 51

use function getline

Question 52

getline

Answer 52

reads until end of current line

Question 53

> >

Answer 53

extracts data from an input stream into a variable

Question 54

«

Answer 54

pushes data into an output stream