1. C++ fundamentals
Lecture 1, Chapter 2 – pp49 -98
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2. Topics to Be Covered A simple C++ program Comments in program
Assigning a value in C++
Constants
Names
Definitions
Expressions
Output statements
A simple application
Summary
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3. A simple program – hello world
include: instructs preprocessor to copy contents of isotream.h and string.h into the program, you can use search to find where they are.
// This is the hello world
#include <iostream>
#include <string>
using namespace std;
void main() {
cout << "hello world" <<endl; }
Says the program will be using objects that are named in a region called std.
cout: character out, note “<<“ and endl
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4. Sample Output
program
Output from DOS
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5. Comments It is a good programming practice to add comments for maintenance purpose
In c++, there are types of comments: // and /*… */
// for a single line
/*….. */ for a block of lines
Example:
//this is the first program
a++; // increment the variable a
Example /*
This is the first program.
It involves comments */
For a block of lines
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6. Example
block
Single line
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7. Assigning a value Assigning a value to x
// This program accepts and output a value
#include <iostream>
#include <string>
using namespace std;
int main() {
//display the following
cout <<"Enter a value (integer)?";
int x; //defines as integer
cin >> x; //input a value
cout << "The ouput of three times your input is" << 3*x <<endl;
return 0; }
Assigning a value to x
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Y K Choi

8. Example
Name of file
output
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9. Constants – a string constant is a sequence of zero or more characters enclosed
Use “ “ to quote a string
If the string consists of “, use backslash \”
Newline \n
Tab \t
Backspace \b
Bell \a
Single quote \”
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Y K Choi

10. Example
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11. Constants – integer, octal, hexadecimal and long
integer: C++ reserves 4 bytes
Example:
Octal: with a leading zero (also 4 bytes)
Example:
Hexadecimal: prefix with 0x or 0X
Example: 0x24 0x1F
Long: with L (reserves 8 bytes)
Example: 12234L
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12. Example
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13. Floating Point 1234 The general format is Mantissa x 10 ^ exponent 67
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14. Names – some words are reserved as part of the language and cannot be used by programmer
Definition are: short, int, long, float, double, char
Identifiers are: main, cout, endl, cin, switch, this, if, else, for, do , while, class, template, asm, auto
You cannot int main //define main as the integer variable
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15. Definitions General format Type ID, ID,,,,,; Example int x, y, z;
float speed, weight, height;
With initialisation
int x = 3, y = 4, z= 5;
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16. Expressions Simple expressions int weight = 123.5;
Binary arithmetic expressions
a = b + c; // add two together
a = 3*6 //18
a = 12/4; //equal to 3
A = 10%3 // remainder, value is 1
Unary expression
int i = 1;
~i; //unary, means 0 – 1
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17. Output statements cout (pronounced as “C out” )
cout << (here << is the insertion operator)
cout << endl; (endl is a special class of object called a manipulator which means to insert a new line and output the stream to the display (VDU)
cout << “CityU”;
cout << endl;
Can be merged into one as follows
cout <<“CItyU” <<endl;
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18. Summary Comments // or /*….. */ Assigning a value, use cin >> m
Constants, 234 (integer), 45.6 (float)
Definition, int a; float f; char c;
Names: cannot use defined words such as main
Expressions, + - * / and %
Output statements, cout
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