Pointers in C: Passing Pointers to Functions, Study Guides, Projects, Research of Software Engineering

Download Pointers in C: Passing Pointers to Functions and more Study Guides, Projects, Research Software Engineering in PDF only on Docsity! POINTERS IN C, PASSING POINTERS TO FUNCTIONS CSSE 120—Rose Hulman Institute of Technology Can functions modify actual parameters?  In Python, no! (pass by value)  Consider this function: void downAndUp(int takeMeHigher, int putMeDown){ takeMeHigher += 1; putMeDown -= 1; }  How is this C function invoked?  downAndUp(up, down);  Will calling the function change the values of the actual parameters up and down? Pointer Assignments 1. int x=3, y = 5; 2. int *px = &x; 3. int *py = &y; 4. printf("%d %d\n", x, y); 5. *px = 10; 6. printf("%d %d\n", x, y); /* x is changed */ 7. px = py; 8. printf("%d %d\n", x, y); /* x not changed */ 9. *px = 12; 10. printf("%d %d\n", x, y); /* y is changed */ Break 7 eee O Starring Binky! Oo (See http: //cslibrary.stanford.edu/104/) Pointer Pitfalls  Don't try to dereference an unassigned pointer:  int *p; *p = 5; /* oops! Program probably dies! */  Pointer variables must be assigned address values.  int x = 3; int *p; p = x /* oops, RHS should be &x */  Be careful how you increment  *p +=1; /* is not the same as … */  *p++;