Input and Output statements

Input/Output Libraries

Input and Output are not part of the Ada language

• provided by special packages
  • text: TEXT_IO
  • integer: define new library
  • float: define new library
  • own types: define new libraries

		package int_io is new TEXT_IO.INTEGER_IO(INTEGER);
		use  int_io;

		package flt_io is new TEXT_IO.FLOAT_IO(FLOAT);
		use  flt_io;

Specify libraries at start of procedure

• compiler knows what types of input/output to use
• binder knows which libraries to link with program
• I/O procedures become available to programmer

Input

• argument is a variable that receives input value
• value must be same type (eg INTEGER) as variable

		PUT ( "Please enter the first number ");
		GET ( number1 ); 

SKIP_LINE

• advance to next line, ignoring unused input
• when prompting for values from a user, always follow GET with SKIP_LINE

		PUT ( "Please enter the first number ");
		GET ( number1 ); skip_line;

		PUT ( "Please enter the second number ");
		GET ( number2   ); skip_line;

		Please enter the first  number 42  10
		Please enter the second number 23

Output

• print argument
• leave the cursor on the same line

			PUT ( "Please enter the first number ");
			GET ( number1 ); skip_line;

			Please enter the first number:  ffffffff

PUT_LINE ("string")

• print string, then move cursor to next line

		
			PUT ( "Please enter the first number ");
			GET ( number1 ); skip_line;

			Please enter the first number:  
			ffffffff

• move cursor to next line

Formatted output

 

PUT(int_val, WIDTH => positive_integer);

		PUT ("The sum of the numbers is:");
		PUT (number1+number2, width=>7);  NEW_LINE;
		PUT ("The product of the numbers is:");
		PUT (number1*number2, width=>3);  NEW_LINE;
		PUT ("The sum of the numbers is:");
		PUT (number1+number2, width=>1);  NEW_LINE;


		The sum of the numbers is:     16
		The product of the numbers is: 48
		The sum of the numbers is:16

PUT(real_val, FORE => positive_integer,
              AFT  => positive_integer,
              EXP  => positive_integer);

		PUT (23.456);  
		PUT (23.456, EXP=>0);
		PUT (23.456, AFT=>3, EXP=>0);
		PUT (23.456, AFT=>2, EXP=>0);
		PUT (23.456, FORE=>3, AFT=>3, EXP=>0);


		' 2.34560000000000E+01'
		'23.45600000000000'
		'23.456'
		'23.46'
		' 23.456'

An example program shows (among other things) the use of input and output statements.