Class 8: I/O

Question 1

Character Based I/O

Answer 1

Int getchar() - input
Int putchar() - output

Question 2

Formatted I/O

Answer 2

Zero or more characters with a requirement to specify the format of the input or output
Int scanf()
Int printf()

Question 3

Int getchar(void)
Int putchar(Int)

Answer 3

These function use the integer (4 byte) values which correpond to a given 1 byte ascii character. The integer must be cast before being assigned to char variables or must be printed with %c format code to be output as a char with printf()

Question 4

ASCII

Answer 4

A character encoding standard that uses 8 bit binary code to represent characters. The ascii table organizes characters and their corresponding binary, decimal, and hexadecimal representations

Question 5

IMPORTANT: scanf ignores ______ but not ________ white space characters when it reads NUMERIC values from input

Answer 5

Leading, following

Question 6

Int int1. Int2;
Scanf(“%2i”, &int1);
Scanf(“%2, &int2);

INputs: 2345

Answer 6

Int1 has value 23
Int 2 has value 45

Question 7

Printf(“%4.3f\n”, x);

Answer 7

Field With: 4
Precision: 3

Question 8

Char s1[64]
Scanf(“%[^\n]”, s1);

Answer 8

Reads the whole line (until new line is encountered)
Hello World

Question 9

Scanf(“%[^\t]%[^\t]”, s1, s2)

Answer 9

Field1<tab>field2</tab>

Question 11

What is the return type of printf()

Answer 11

It returns the NUMBER of characters printed

Question 12

If you use scanf() to read in the value of a character array, should you use &

Answer 12

No because the name of the array is a const pointer to the first character of the string

Question 13

If you use scanf() to read and integer (%d), how does it work

Answer 13

Scanf will skip white space characters (space, tab, new line) until it encounters first non whitespace character. Because it expects to read integer, it expects to find digits character or + or -. Scanf() continues reading until it encounters a non digit. It then conclude that is has reached the end of the integer. Scanf() places the non digit back into the input. This means that the next time program goes to read the input, it starts at the previously rejected non digit characters.

Question 14

Using scanf to read string %s

Answer 14

If you use %s, any other character other than whitespace is acceptable, so scanf skips whitespace to the first non-whitespace character and saves up non-whitespace characters until hitting whitespace again.

Question 15

Scanf using %c

Answer 15

If you use scanf() to read a character, all input characters are fair game. If the next input character is a space or new line, a space or new line is assigned to the indicated variable; whitespace is not skipped

Question 16

What is the return value of scanf()

Answer 16

The function returns the number of items that it successfully read. If it reads not items, scanf() returns 0. It returns EOF when it detects a condition known as “end of file”

Question 17

Int getchar()

Answer 17

Getchar() returns an integer value which correpond to a give 1-byte ascii character, the integer must be CAST before assigning it to a char variable or must b printed with %c format code to be output as a char with printf()

Question 18

Int putchar(int)

Answer 18

/the int value returned can be ignored/