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           Faculty of Applied Science and Engineering, University of Toronto
                     CSC181: Introduction to Computer Programming, Fall 2000

Tutorial Notes, Week 2
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-----------------
Summary of Topics
-----------------

- A basic C program
- Introduction to 'if' and 'while'

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Example
-------

The following program reads in 5 integers and returns the maximum of
those integers:

#include <stdio.h>

main() {

  int n = 0;
  int max = 0;
  int i = 0;

  scanf("%d", &max);
  i = 1;
  while (i != 5) {
	int temp = 0;
	scanf("%d", &temp);
	if (temp > max) {
	  max = temp;
	}
	i++;
  }

  printf("maximum: %d", max);
}

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Sample Run
----------

5
2 8 3 9 1
maximum: 9

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'if' and 'while'
----------------

Some notation:

- expression

  A formula that evaluates to false (zero) or true (non-zero).

- statement

  A single statement or a compound statement, i.e. a group
  of statements enclosed in braces.

An if-statement is a "selection" statement, one that allows for
conditional execution of statements.

- The most basic form:

  if (expression)
    statement

  'statement' is executed if 'expression' is true.

- 'if' can be used in conjunction with 'else':

  if (expression)
    statement1
  else
    statement2

  If 'expression' is true, execute 'statement1', otherwise execute
  'statement2'.

- 'else' can be combined with 'if' to form 'else if':

  if (expression1)
    statement1
  else if (expression2)
    statement2

  If 'expression' is true, execute 'statement1'. Otherwise, if
  'expression2' is true, execute 'statement2'.

Refer to King, Section 5.2 for more details.

A while-statement is an "iteration" statement, one that allows for
repeated execution of statements.

- The most basic form:

  while (expression)
    statement

  'statement' is executed repeatedly as long as 'expression' is
  true. (If the 'expression' initially evaluates to false, then
  'statement' will never be executed.)

Refer to King, Section 6.1 for more details.

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Exercises
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1. Write a program that reads in 2 integers x and y and prints all
   of the integers in between x and y (inclusive), one per line.

2. Write a program that reads in an integer and prints all of its
   divisors, one per line. (Hint: You will need the modulo operator,
   '%'; 'x % y' evaluates to the remainder from dividing x by y.)

3. Write a program that reads in 5 integers and prints how many times
   the number 4 occurs among those integers.

4. Write a program that reads in 5 integers and prints "There is at
   least one negative integer" if at least one of the integers is
   negative.