Upload
gwenda-owen
View
227
Download
1
Embed Size (px)
Citation preview
A first program
1. #include <iostream>
2. using namespace std;
3. int main() {
4. cout <<“\tHello World\n";
5. return 0;
6. }
function name
type of returned value
argument
Line 2. main() function, entry point
int main()
Next Slide
Line 3. Use cout to display information
cout << “\tHello World\n”;
\t is a tab \n is a new line
Redirection (insertion)
Next Slide
cout <<"A big number:\t"<<70000<<endl;
Output
A big number: 70000
Another example cout
Tab moves to nextposition
Another way ofForcing a new line
cout <<"The sum of 8 & 5 is "<<8 + 5<<endl;
Output
The sum of 8 & 5 is 13
Yet another example of cout
Calculations
Getting information from the user using
cin,usually paired with cout
cout << “Enter a number: “;cin >> num1;
The contents of the address named num1
is ...
Extraction operator
cout << “Enter 3 numbers: “;
cin >> num1 << num2 << num3;
The contents of the address named num1 is …num2 is …num3 is ...
A Look at cin
Reserved Words
Words that have special meanings in the
language. They must be used only for their
specified purpose. Using them for any
other purpose will result in a error.
e.g. cout do if switchcin while else return
*
Reserved Words
C++ is case-sensitive.
Thus:
cout COUT Cout cOut
are all different.
The reserved words are all in lowercase.
Statements
A statement controls the
sequence of execution, evaluates
an expression, or does nothing,
and ends with a semicolon.
Statements
{
cout <<"A fraction: "<<5.0/8.0 <<endl;
cout <<"Big # : "<< 7000.0*7000.0<<endl;
cout <<8 + 5 <<" is the sum of 8 & 5\n";
cout << “Hello world”;}
There are 4 statements in this block.
Block denoted byCurly braces
Comments, for PDL to Code
These are important parts of a program.
Two types of comments
// ignore rest of line
/* ignore between these */
or /*
ignore over
These lines
*/
Programming Style
one main() function and use consistent layout of braces
int main ( ) {statements;
}
indent
open
close
Declaration statementsAny variable must be declared (announced) before it is used.
This is a law of C/C++.Declaration instructs compiler to reserve memory to store
values#include <iostream>Using namespace std;
int main() {int num1;cout << “Enter a number: “;cin >> num1;cout << “You entered number “ << num1 << endl;return 0;
}
declaration
Programming Style
Group declarations at the beginning, just after the opening brace of main
void main () {declaration statements;
other statements;}
Programming Style
Put blank lines before and after control structuresint main () { declaration statements;
statements
if (expression){statement;statement;
}
statements;}
int
Any number +ve or –ve without a decimal point.
Will truncate (cut off) any decimal points E.g. 5/8 is 0 not 0.625 * big cause of errors E.g 15/2 is 7 not 7.5
float or double
Sometimes called real. Contains decimal point. Precision
Accuracy, note computers have problems with accuracy of floating point numbers.
E.g. Pi Default is 6 significant digits
Exponential notation E.g. 7000.0 is 7.0e+03
char
A single character, letter or digit.
Enclosed in single quotes ‘A’ ‘a’ ‘1’ Stored using ascii code.
Simple strings with char []
To input non numeric data, like names, and addresses, use character arrays. char FirstName[20] stores a string of up
to 20 characters.
Simple String Example
#include <iostream>using namespace std;
int main(void) {char FirstName[10];
cout << "Enter your first name : ";cin >> FirstName;cout << "Hello " << FirstName << endl;return 0;
}
Demonstration – PDL –Code incremental development
Pendulum problem
Create defining diagram
Inputs Processes Outputs
period Intitialise g,Pi.
Get period
Compute Plength
Plength
PDL for pendulum
1. Assign 9.8 to g
2. Assign 3.142 to Pi
3. Prompt for a period in seconds
4. Calculate the length in metres
5. Display length for required period
Use formula (given) length = g*(period/2*Pi)2
Start Visual C++ environment
Create console project in new solutionSelect Empty Project in Application SettingsCreate new C++ source file – add to projectEnter skeleton programCheck it works!Enter design as commentsAdd program description comment at topTest!Expand design one line at a time testing as you go