Science Computer 310 Fall 1999 Test 3
Closed book. Closed notes.
Name__________
I. Passing parameters (25 points (6/6/6/7) )
Consider the following c program. void q1( int a, int b, int c) { a = a + 1; b = c*2; c = a; } void main() { int x[]={1,2,3,4,5 }; int y = 3; int z = 1; q1( z, x[z], y); for (int i=0; i<4; i++) cout << x[i] << " " ; cout << y << z << endl; } Show the output produced when the program is executed with each of the following parameter passing techniques: A: Value _______________________________________________________ B: Reference _______________________________________________________ C: Name _______________________________________________________ Explain how binding times explain the difference between passing parameters by reference and passing by name in the example above.
II. Multi-dimensional arrays (10 points)
Passing multidimensional arrays as parameters demands special attention. Consider the following function prototype. void trythis( int x[10][]); Based solely upon this prototype, would it be more likely that this language stores a 2dimensional array in row-major or column-major order. Why?
III. Activation Records (20 (15/5) points)
Procedure BIGSUB; Procedure A; Procedure B; Begin {B} . . . End; {B} Procedure C; Begin {C} . . . B; . . . End {C}; Begin {A} . . . C; . . . End {A} Begin { BIGSUB } . . . A; . . . End { BIGSUB }
DL SL
DL SL
DL SL
DL SL
DL SL
Show the stack with all activation record instances, including static (SL) and dynamic chains (DL), when execution reaches the position indicated by the arrow in the skeletal block-structured program. Assume BIGSUB is at the level 1. Explain the difference between the static and dynamic chains.
IV. Concurrency (30 points (8/5/5/3/3/3/3) )
A.
Give an example of each: physical and logical concurrency
B.
Define cooperation synchronization.
C.
Define competition synchronization.
D.
fork() is a concurrency mechanism available in most languages implemented in Unix. What is the effect of calling fork()?
What happens to variables in the program when fork() is called?
What happens if a file stream is open when fork() is called?
How does a process know whether it is the parent or the child?
III. Concurrency Examples (20 points (4/4/4/4/4) )
A. Show the output produced by each of the following examples:
#include <> main() { cout << "A"; fork(); cout << "B"; fork(); cout << "C"; } #include <> main() { cout << "A"; if (fork()==0) {cout << "B"; fork(); cout << "C"; } }
OUTPUT:
OUTPUT:
There are many correct answers to the two previous questions! Give a DIFFERENT correct answer for each of these examples. OUTPUT: OUTPUT:
Explain why there are multiple correct answers to the examples.