Topics covered on Wednesday, 2010-08-11

Sample Program (compute1.cpp)

     1  // compute1.cpp
     2  // Prompt user for 2 numbers and and operation (+ or -) and
     3  // print out result of the operation
     4  // Copyright (C) 2010, Raj Mathur
     5  #include <iostream>
     6  #include <cstdlib>
     7  using namespace std;
     8  int main(int argc, char *argv[])
     9  {
    10    char
    11      op;
    12    int
    13      number_1 = 0;
    14    int
    15      number_2 = 0;
    16    int
    17      result;
    18    // Get operation type (p == plus, m == minus)
    19    cout << "Enter operation: (p)lus or (m)inus: ";
    20    cin >> op;
    21    // Get values to be used for computation
    22    cout << "What is the first number? ";
    23    cin >> number_1;
    24    cout << "What is the second number? ";
    25    cin >> number_2;
    26    // Check operation and do it
    27    if( op == 'p' )
    28    {
    29      result = number_1 + number_2;
    30    }
    31    else if( op == 'm' )
    32    {
    33      result = number_1 - number_2;
    34    }
    35    else
    36    {
    37      cerr << "Only operations (p)lus and (m)inus are permitted, sorry" << endl;
    38      exit(1);
    39    }
    40    // Display it
    41    cout << "The result is: " << result << endl;
    42    exit(0);
    43  }

• The if statement checks a condition and executes the following code if the condition is true.
• If the condition is not true, the else portion is executed.
• C++ treats all non-zero values as true and 0 as false when evaluating conditions.

Comparison Operators

a == b

a != b

a < b

a <= b

a > b

a >= b

Logical Operatots

c1 && c2

c1 || c2

!c1

Sample Program (compute1.cpp) revisited

     1  // compute1.cpp
     2  // Prompt user for 2 numbers and and operation (+ or -) and
     3  // print out result of the operation
     4  // Copyright (C) 2010, Raj Mathur
     5  #include <iostream>
     6  #include <cstdlib>
     7  using namespace std;
     8  int main(int argc, char *argv[])
     9  {
    10    char
    11      op;
    12    int
    13      number_1 = 0;
    14    int
    15      number_2 = 0;
    16    int
    17      result;
    18    // Get operation type (p == plus, m == minus)
    19    cout << "Enter operation: (p)lus or (m)inus: ";
    20    cin >> op;
    21    // Validate operation
    22    if( op != 'p' && op != 'm' )
    23    {
    24      cerr << "Please enter only 'p' for plus and 'm' for minus." << endl;
    25      exit(1);
    26    }    
    27    // Get values to be used for computation
    28    cout << "What is the first number? ";
    29    cin >> number_1;
    30    cout << "What is the second number? ";
    31    cin >> number_2;
    32    // Do the operation
    33    if( op == 'p' )
    34    {
    35      result = number_1 + number_2;
    36    }
    37    else
    38    {
    39      result = number_1 - number_2;
    40    }
    41    // Display it
    42    cout << "The result is: " << result << endl;
    43    exit(0);
    44  }