CP2003 - Tutorial Two

1. Show the lifetimes of the variables in the following C program and indicate which are statically vs. dynamically allocated.

    int m;

    void S () {
      float z;

      z = 1.0;
    }

    void R (int n) {
        if (n > 0)
          R(n-1);
        S();
    }
  
    int main() {
      m = 3;
      R(1);

      return 1;
    }

Note that R will be activated twice, recursively.

2. In the following C program skeleton, identify all the name spaces by stating to which name space each name belongs. Also indicate the scope of each name. Note, C has static scoping.

    int x, y, z;

    int foo() {
       {
         int x;
       }
    }

    foo2(int x) {
       int y;
    
    }

    main() {
       int y;

    }

3.Can you explain what is wrong with the following Pascal program in terms of name-spaces and scopes? What about if Pascal had dynamic scoping?

   program scope;
     procedure foo()
       begin
       end;
     procedure foo()
       begin
       end;
     begin
       foo();
     end;

4. In terms of name spaces and scopes, is the difference between variable x and variable y in the following Pascal program?

   program scope;
     var x: integer;  
     procedure foo()
       begin
       end;
     var y: integer;  
     begin
       foo();
     end;

5. Identify all the kinds of declarations in the following C program.

   int  x;
   typedef int shortInt;
 
   int foo(int z, int *q) {
      int y;
 
      return z + *q;
   }
 
   void main() { }

6. Using the following C program discuss what bindings exist in the environments (global environment, main environment, foo environment) at various points in the code. Note that C has static binding or scoping.

   int  x;                 
   char hello;
 
   int foo(int z, int q) {      
      int y;
 
      return z + q; 
   }
 
   void main() {
      int y[30];              
      char *str;         
    
      str = "hello";
      y[1] = foo(23, 34);
      str = "good-bye";
   }

7. Explain specifically why GOTO is considered harmful.

8. Does C have multiple assignment? Does it have collateral assignment?

9. Assume that the collateral operator is ``,'' and that the sequential operator is ``;''. Rewrite the following program using the collateral operators whenever you can (hint: look for read/write conflicts).

   x = 4;
   y = 23;
   z = x + y;
   printf("%d", z);
   x = foo(x, y, z);

10. Discuss an important problem with the following code. Run the program and check the output of the program

#include<stdio.h>

int *foo() {
        int x;
        x = 2;
        return &x;
     }

int foo1(){
	int y=675;
	int z=90;
	return y;
}
   
void main() {
       int *x, *foo();

       x = foo();
	   foo1();
       printf("%d", *x);
     }

11. Why is a language that only supports allocation of static storage items limiting?

12. In many programming languages strings are defined to be arrays of characters. Compare the consequences of this when a string variable is:

1. a static array
2. a dynamic array
3. a flexible array

Consider string operations such as assignment, concatenation, and comparison.