Sections 0101, 0102, 0103 and Honors, Fall 1995

Tuesday November 21, 1995

Assigned Reading: 13.1 - 13.2

Handouts (available on-line): Project 5

Topics Covered:

• We looked at a strange error that occurs when you use the variable name strlen as the name of a global variable in the following program and sample run. This problem occurs because the function GetLine calls a function named strlen in the standard UNIX string library. The linker/loader thinks that this function is referring to the global variable named strlen instead of the function in the library. The correct way to avoid such problems is to make your global variables static when they are not used by functions in other files. (If you have to use global variables from other files, then you have to be very careful about what you name them.) The following program and sample run shows that the weird error goes away when the global variables are declared to be static.

• We reviewed the previous lecture on pointers. In this program and sample run, we use dereferenced integer pointers in integers expressions just like any other integer variable.

• We use pointers in this program to pass integer variables to a function by reference. The function stores the number of hours and minutes in the variables whose addresses are stored in the parameters. Sample run.

• We examined parameter passing by reference in greater detail in the next example. Program and sample run.

• Using parameters passed by reference makes it possible to write a function that swaps the contents of two variables Program and sample run.

• Discussed Project 5