Counting Positive and Negative Input Values

Problem Statement

Given a set of integer input values, write a program to count the number of positive and negative values and compute their sums.

The input is organized as follows:

For example, the following input shows that there are seven input values (i.e., the 7 on the first line), -6, 7, 2, -9, 0, 8 and 0. 
7
-6
7
2
-9
0
8
0

Solution 

! ---------------------------------------------------------
! This program counts the number of positive and negative
! input values and computes their sums.
! ---------------------------------------------------------

PROGRAM  Counting
   IMPLICIT  NONE

   INTEGER :: Positive, Negative
   INTEGER :: PosSum, NegSum
   INTEGER :: TotalNumber, Count
   INTEGER :: Data

   Positive = 0                    ! # of positive items
   Negative = 0                    ! # of negative items
   PosSum   = 0                    ! sum of all positive items
   NegSum   = 0                    ! sum of all negative items

   READ(*,*)  TotalNumber          ! read in # of items
   DO Count = 1, TotalNumber       ! for each iteration
      READ(*,*)  Data              !    read an item
      WRITE(*,*) 'Input data ', Count, ': ', Data
      IF (Data > 0) THEN           !    if it is positive
         Positive = Positive + 1   !         count it
         PosSum   = PosSum + Data  !         compute their sum
      ELSE IF (Data < 0) THEN      !    if it is negative
         Negative = Negative + 1   !         count it
         NegSum   = NegSum + Data  !         compute their sum
      END IF
   END DO

   WRITE(*,*)                      ! display results
   WRITE(*,*)  'Counting Report:'
   WRITE(*,*)  '   Positive items = ', Positive, ' Sum = ', PosSum
   WRITE(*,*)  '   Negative items = ', Negative, ' Sum = ', NegSum
   WRITE(*,*)  '   Zero items     = ', TotalNumber - Positive - Negative
   WRITE(*,*)
   WRITE(*,*)  'The total of all input is ', Positive + Negative

END PROGRAM  Counting
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Program Input and Output

If the data shown above is stored in a file, say data.in and the above program is compiled to an executable count, then executing 
count < data.in
will generate the following output: 
Input data 1: -6
Input data 2: 7
Input data 3: 2
Input data 4: -9
Input data 5: 0
Input data 6: 8
Input data 7: 0

Counting Report:
   Positive items = 3 Sum = 17
   Negative items = 2 Sum = -15
   Zero items     = 2

The total of all input is 5

Discussion

In the program, Positive and Negative are used to count the number of positive and negative data items, and PosSum and NegSum are used to compute their sums. The program first reads the number of input items into TotalNumber and uses it as the final value in a DO-loop.

This loop iterates TotalNumber times. For each iteration, it reads in a new data into Data. The IF-THEN-ELSE-END IF statement tests to see if it is positive or negative, adds 1 into the corresponding counter, and adds the value into the corresponding sum. Note that the number of zero items are not counted, since TotalNumber - Positive - Negative gives the number of zero items. The sum of all zero items are not calculated either, since it must be zero!