Read/Write

The input and output is achieved by using keywords, READ and WRITE (or PRINT) respectively.

The syntax of input statement:

READ (input_device, format[, options]) list_of_variables

READ format, list_of_variables (standard input device, usually the keyboard)

For example

READ (*,*) A, B, C

the input device * indicates that data is read from the standard input device (usually the keyboard); the format * indicates that it is free format and the computer will decide how to format; the program is expecting 3 numbers entered from keyboard and those three numbers will be stored in the three variables A, B and C.

The statement can also be replaced by

READ *, A, B, C

The syntax of output statement:

WRITE (output_device, format[, options]) list

PRINT format, list (standard output device, usually the screen)

For example

WRITE (*,*) ‘A=’, A, ‘B=’, B, ‘C=’, C

the output device * is to use the standard output device ( usually the screen); the format * means that it is free format and the computer decides how to format; the list consists of character strings (inside ‘ ’) and variables; data in the variables will be displayed instead of the variable names.

This statement can be replaced by

PRINT *, ‘A=’, A, ‘B=’, B, ‘C=’, C

If A, B and C have data of 1, 2 and 3 respectively, the output will be

A=1 B=2 C= 3

Exercises

1). Give an example of using READ to input 2 real numbers and 1 integer number (declare the variables before the READ statement).

2). Write the output statement in the following program.

integer a, b, c

read(*,*) a, b

c = a + b

<output statement>

end

For example, if numbers in a and b are 5 and 6, the output should be displayed as

5 + 6 = 11

3). Type in the following program to a file (cylinder.f95), and then compile it. You should find the program has mistakes. Correct the mistakes and run the program.

!

! Your name, Group

! Date

!

! finds surface area and volume of a cylinder

!

Program cylinder

IMPLICIT NONE

pi = 4*atan(1.0)

write(*,*)'diameter of cylinder?'

read(*,*)dia

write(*,*)'length of cylinder?'

read(*,*)length

sarea = pi*dia*length

vol = pi*(dia**2)*length/4.

write(*,*)' '

write(*,*)'diameter of cyl. =',dia

write(*,*)'length of cyl. =',length

write(*,*)'surface area of cyl. =',sarea

write(*,*)'volume of cyl. =',vol

stop

end program cylinder

4). Write a program (TrigonometricFunctions.f95) that reads an angle in degrees from the keyboard and prints out the sine, cosine, and tangent of the angle in the form given below:

deg = 30.0000

sin(deg) = 0.5

cos(deg) = 0.866025388

tan(deg) = 0.577350259