CMSC104

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Lecture 17: Functions 3

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Powerpoint Slides:  none

Reading Assigned:   

Homework Due: 

Homework Assigned: 

Topics Covered:

• Return and discuss Quiz 2.
• Finish up local variables.
• Parameter passing by reference.
• Classwork 17.

Programs Shown:

• Uninitialized local variables have garbage value: garbage1.c and garbage2.c.
  THESE TWO PROGRAMS DEMONSTRATE A VERY BAD BUG. DO NOT COPY.

• If formal parameters and actual parameters do not have the same type, the C compiler tries to convert the values if it can: promote.c.

• We try to write a function that swaps the values in two varialbles:
  • The first attempt does nothing: swap1.c
  • The second attempt uses reference parameters to accomplish this: swap2.c
  • This example shows what happens if you forget the &'s in the actual parameters: swap3.c.

• Here's an artificial example to help us understand reference parameters: ref_par.c.

• This example includes a function that determines how many hours and minutes make up a given number of minutes: minutes.c.