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Summary

Learn about function prototypes, definitions, calls, and parameter rules. Understand call-by-reference and call-by-value concepts. Practice with sample code and outputs to enhance comprehension.

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  1. Summary • Assignment: Wednesday, October 29, 2003. • Last time we talked about functions: • A function consists of: • Function Prototype • Function Definition • Function Call • Rules of parameter list. • Call by reference & call by value. CS150 Introduction to Computer Science 1

  2. void changeIt (int, int&, int&); void main() { int i,j,k,l; i = 2; j = 3; k = 4; l = 5; changeIt(i,j,k); cout << i << j << k << endl; changeIt(k,l,i); cout << i << k << l << endl; changeIt(i,j,j); cout << i << j << endl; changeIt(i,i,i); cout << i << endl; } void changeIt(int a, int& b, int& c) { a++; b += 2; c += a; } What is the output? CS150 Introduction to Computer Science 1

  3. #include <iostream> void changeIt(int, int&, int&); void main() { int i,j,k,l; i = 2; j = 3; k = 4; l = 5; changeIt(i, j, k); cout << i << j << k << endl; changeIt(k,l,i); cout << i << k << l << endl; } void changeIt(int j, int& i, int& l) { i++; j += 2; l += i; } What is the output? CS150 Introduction to Computer Science 1

  4. Program • Write a function to compute the sum and average of two integers, and return the values of sum and average. • An example function call would look like: compute (4, 5, sum, average); CS150 Introduction to Computer Science 1

  5. Scope • Variables have scope - places in the program where they can be referenced. • Local scope - valid only in function or main program. • Global scope - valid anywhere in program. • We will use local variables most of the time. CS150 Introduction to Computer Science 1

  6. Example void computeSum(int, int); int sum; void main() { int i,j; cin >> i >> j; sum = 0; computeSum(i,j); cout << sum << endl; } void computeSum(int num1, int num2) { sum = num1 + num2; } CS150 Introduction to Computer Science 1

  7. Example int computesum(int, int); void main() { int i,j; cin >> i >> j; computesum(i,j); cout << sum << endl; } int computesum(int num1, int num2) { int sum; sum = num1 + num2; return sum; } CS150 Introduction to Computer Science 1

  8. Example int computesum(int, int); void main() { int i,j,sum; cin >> i >> j; sum = computesum(i,j); cout << i << j << sum << endl; } int computesum(int num1, int num2) { int i; i = num1 + num2; return i; } CS150 Introduction to Computer Science 1

  9. Example void silly(float); void main() { float x, y; x = 23; y = 5; silly(x); cout << x << y << endl; } void silly(float x) { float y; y = 25.0; x = y; } CS150 Introduction to Computer Science 1

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