C Formatted InputOutput

1
C Formatted Input/Output

• Formatted output printf
• Conversion Specifiers
• Field Widths and Precision
• Flags
• Escape Sequences
• Formatted input scanf
• Conversion Specifiers

2
Formatted Output - Printf

• int printf(char format, arg1, arg2, )
• Translates internal values to characters
• Returns the number of characters printed

3
Conversion Specifiers

• d, i (int)
• Signed decimal integer
• u (int)
• Unsigned decimal
• o (int)
• Unsigned octal integer
• x, X (int)
• Unsigned hexadecimal

• f (double)
• m.dddddd
• e, E (double)
• m.dddddxx
• g, G (double)
• In f or e style
• h or l (int)
• Put before integer specifier for short or long
  integers

4
Conversion Specifiers

• c (int)
• Single character
• s (char )
• Character strings

• p (void )
• pointer
• Print a

5
Field Widths and Precision

• Between and conversion character
• Number for minimum field width
• Period to separate field width from precision
• Number for the precision
• Strings maximum number of characters
• Number of digits after the decimal point
• Minimum number of digits for an integer

6
Flags

• Between and conversion character
• Minus sign (-) for left justification
• Plus sign () to display plus or negative sign
  for numbers
• Space ( ) put a space before positive number
• Pound sign () to put 0 for octal, 0x for
  hexadecimal, force a decimal point for floats
• Zero (0) to pad a field with leading zeros

7
Example Code

• int main()printf("9s9d9c9f\n","aloha",5,'Z',
  5.67)
• printf("-9s-9d-9c-9f\n",
• "aloha",5,'Z',5.67)
• printf("-9.3s-9.3d-9.3c-9.3f\n",
• "aloha",5,'Z',5.67)
• return 0
• /
• aloha 5 Z 5.670000
• aloha 5 Z 5.670000
• alo 005 Z 5.670
• / (See example1.txt)

8
Example Code

• include ltstdio.hgt
• int main()
• int x 64
• double y 64.0
• printf( "o\n", x ) /0100/
• printf( "x\n", x ) /0x40/
• printf( "X\n", x ) /0X40/
• printf( "g\n", y ) /64.0000/
• printf( "E\n", y ) /6.400000E01/
• return 0
• (See example2.txt)

9
Escape Sequences

• Move the cursor
• \b one back
• \n beg. of next line
• \r beg. of current line
• \t next horizontal tab

• Output respective character
• \ \ \? \\
• Annoying alert sound
• \a

10
Formatted Input - Scanf

• int scanf(char format, arg1, arg2, )
• Read characters and store by format
• Arguments must be pointers
• Returns the number of successfully matched and
  assigned input items
• Stops when format string ends, or if input does
  not match input specification
• Skips blanks and tabs

11
Conversion Specifiers

• Reading integers (put before character)
• d signed decimal
• i signed octal, decimal, or octal
• o an octal value
• u unsigned decimal
• X, x hexadecimal
• h or l place before integer specifier for short
  long integers

12
Example Code

• include ltstdio.hgt
• int main()
• int m0 float d0 char y10 0
• printf( "Enter a date (mm dd yyyy) " )
• scanf( "d f s", m, d, y )
• printf("monthd dayf years\n", m, d, y
  )
• return 0
• /
• Enter a date (mm dd yyyy) 3 3 2003
• month3 day3.000000 year2003
• Enter a date (mm dd yyyy) 3-3-2003
• month3 day-3.000000 year-2003
• Enter a date (mm dd yyyy) 3/3/2003
• month3 day0.000000 year
• / (See
  example3.txt)