Data is required to be fed into the program (input) and sent out of the program (output). Considering the draughtsman using a CAD station, the input is his commands to cause lines/circles to be drawn etc, the output is the actual drawing on the screen. General input is by means of the C command scanf. The syntax of the simplest input statement is: -
scanf(" format of variable",&variable name)
e.g scanf("%f",&number1); expects a floating number input
scanf("%d",&number1); expects a integer number input
scanf("%c",&number1); expects a single character number input
scanf("%x",&number1); expects a hexadecimal number input
Note '&' means address operator.
Data is output by means of the printf command. The simplest syntax of the printf statement is: -
printf(" string format controls ",variables);
printf("%f",number1); prints a floating number from the variable number1
printf("%d",number1); prints a integer number from the variable number1
printf("%c",number1); prints a single character from the variable number1
printf("%x",number1); prints a hexadecimal number
Within the syntax above we have mentioned 'controls' it is possible to include special screen controls in the format specification i.e. new line \n , carriage return \r, tabulate \t.
printf("%f\n\r",number1); prints a floating number from the variable number1 with a new line and carriage return Likewise we can include a literal string within the format specification i.e. actual words
printf(" The value is %f contained in the variable number1 \n\r",number1);
This prints literal text and a floating number from the variable number1 with a new line and carriage return.