#1 Basic Computer Concepts

Basic computer concepts

Programming languages

First sample program

#include 

int main()
{
	// Declare two integer variables
	int theInt, theIntSquared;

	// Prompt for input and retrieve an integer
	cout << "Enter an integer: ";
	cin >> theInt;

	// Perform calculation
	theIntSquared = theInt * theInt;

	// Display the result
	cout << theInt << " squared is " << theIntSquared << endl;

	// These next few lines may not be necessary
	// for some compilers/environments
	
	// Declare a character variable
	char wait;
	// Wait for user to input a character
	cin >> wait;

	// Indicate success status to OS
	return 0;
}

Variables

Simple types

bool
constants: true, false

char
constants: 'j', '2', '\n', '\t', '\\', '\0', '\''

int
constants: 52, -3, 072, 0xF1F1

double
constants: 3.1415, -4.0, 8.27E18, 1.5e-5

string constants
"Hello, world!\n", "\"Hello, world\" I said.", ""

Constant variables

	const double Pi = 3.141592;
	const int MAX_GUESSES = 10;

Variable assignment

	theIntSquared = theInt * theInt;
	x = y = z = 0;
	x = 5 + (z = 2);

Arithmetic operators

+ - * / %

Examples:

7 / 2 -> 2
7.0 / 2 -> 3.5
double(7) / 2
6.0 / 2 -> 3.0
1/2 -> ?

54 % 7 -> 5

int x, y = 6;
double z = 5.2;
x = y * z;
int * double -> double, int = double -> ?

Precedence and order of evaluation

Highest to lowest:
()
* / %
+ -
=
Left to right: * / % + -

Right to left: =

Undefined: ()

Examples:
8 + 6 * 4 / 2 - 1 = (8 + ((6 * 4) / 2)) - 1
x = y = z = 0 -> x = (y = (z = 0))

Shortcut assignment operators

+= -= *= /= %= ++ --

theInt = theInt + 5 ==> theInt += 5
theInt = theInt + 1 ==> theInt += 1 ==> theInt++
theInt++ vs. ++theInt

Same precedence as =: += -= *= /= %=

Higher precedence than */%: ++, --

Expression evaluation program

int main()
{
	int m, n = 2;

	// This expression does nothing (has no "side-effects")
	1 * 2 + 3 / 4 - 5 - 6 + 7 - 8;

	// This one is equivalent to n = n + 6
	n += 6;
	cout << "n = " << n << endl;

	// This one is equivalent to n = n / (2 + 1)
	n /= 2 + 1;
	cout << "n = " << n << endl;

	// This is equivalent to n = n + 1, or n += 1
	n++;
	cout << "n = " << n << endl;

	// What's the result here?
	m = n++;
	cout << "m = " << m << ", n = " << n << endl;

	// How about here?
	m = ++n;
	cout << "m = " << m << ", n = " << n << endl;

	// This expression has unpredictable side-effects.
	n = (n = 10) * 4 + (n = n * 10) * 2;
	cout << "n = " << n << endl;

	return 0;
}
Output: 
n = 8
n = 2
n = 3
m = 3, n = 4
m = 5, n = 5
n = 240

Standard Input & Output

Input stream (istream) cin

Output stream (ostream) cout

cin >>
cin >> anIntVar >> aDoubleVar >> aCharVar;

cout <<
cout << anIntVar + 2 << aDoubleVar / 3 << aCharVar;

Double value output formatting (consider this a formula)
cout.setf(ios::fixed)
cout.setf(ios::showpoint)
cout.precision(2);

Lab:

Input a length given in whole centimeters. Convert to inches (cm / 2.54) and output the number of whole feet and remaining inches. You may convert double to int using a typecast, even though the effect of doing so is compiler dependent (most compilers truncate). Display inches to 2 decimal places.

Ex. 100 cms = 3 ft. 3.37 in.