Computer Science 117 Summer 2002, Session III
Test, July 26, 2002

1. Assume that M and N are integer variables with the values -3 and 5, respectively, X and Y are real variables with the values -3.57 and 4.78, respectively. Find the type and value of each expression. Do not request permission to use a calculator. It's not necessary, nor even helpful. [5 points each]
   1. NINT(X+Y+1/2)
      INTEGER, 1 (1/2 has the value 0)
      
   2. SQRT(Y) < N
      LOGICAL, true
      
   3. 3.5 > REAL(7/2)
      LOGICAL, true
      
   4. MOD(M+12,N)
      INTEGER, 4
2. Write a logical expression to express the given condition. You may assume that X, Y are variables of type REAL, M, N are variables of type INTEGER, and P, Q are variables of type LOGICAL. [5 points each]
   1. At least one of the variables X, Y, and Z, has a positive value.
      X > 0 .OR. Y > 0 .OR. Z > 0
      
   2. Either P is true, or Q is false.
      P .OR. .NOT. Q
      
   3. 0 < M < N
      0 < M .AND. M < N
      
   4. Either N is zero, or the fraction M/N is greater than 1/2. (Warning: evaluation of this expression must never result in a run-time error.)
      N == 0 .OR. N > 0 .AND. M > 2*N .OR. N < 0 .AND. M < 2*N
3. Write a block of Fortran 90 code which prints out all the integers from 1 to N in reverse order. You may assume that I and N are variables of type INTEGER. Do not write any specification statements or any input statements. [10 points]
   DO I = N,1,-1
   PRINT*,I
   END DO
   
4. Write a block of Fortran 90 code which sets a variable Sum of type INTEGER equal to the sum of the squares of all even positive integers which do not exceed the value of a variable N of type INTEGER. Use I as the index of your loop; you may assume that I is a variable of type INTEGER. Do not write any specification statements or any input or output statements. [10 points]
   SUM = 0
   DO I = 2,N,2
   SUM = SUM + I*I
   END DO
   
5. Write a block of Fortran 90 code which sets a variable X of type REAL equal to the square root of the value of a variable N of type INTEGER, provided the value of N is positive. If the value of N is not positive, X should be set to 0. Do not write any specification statements or any input or output statements. [10 points]
   IF (N > 0) THEN
   X = SQRT(REAL(N))
   ELSE
   X = 0.0
   END IF
6. Consider the following block of FORTRAN 90 code, where I and N are both variables of type integer:
   I = 1
   DO WHILE (I < N)
   PRINT*,I
   I = 2*I
   END DO
   What will the output be if the value of N is 1000? [5 points] 1
   2
   4
   8
   16
   32
   64
   128
   256
   512
7. Recall Project 2, where you computed the area of triangle, given the lengths of the three sides a, b, c, using the formula sqrt(s(s-a)(s-b)(s-c)), where s is the semi-perimeter. In the program that you wrote for this project, what was the identifier you used for the semi-perimeter? (I don't want to know what identifier you think you should have used, but the one that you actually used.)