Transcript C++Review_P1

A Review of C++
Dr. Nancy Warter-Perez
June 16, 2003
Overview
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Overview of program development
Review of C++
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Basics
1-D Arrays and loops
I/O streams
Example amino acid search program
Programming Workshop #1
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Compilers & Development Software
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In this program, we’ll use Visual C++
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Can use any C++ development software
but only source files
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workspaces and projects are not portable
Do your work on either the hard disk or zip
disk (not floppy disk, A: drive – too slow!)
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Program Development
Problem
solving
Problem specification
Algorithm design
Test by hand
Implementation
Code in target language
Test code / debug
Program
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C++ Basics - Comments
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C++
// line comment
/* multi-line comment */
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Header comments
//
//
//
//
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Description of program
Written by:
Date created:
Last Modified:
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C++ Basics - Variables
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Variables have a data type and name or
identifier
Identifiers
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Have the following restrictions:
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Must start with a letter or underscore (_)
Must consist of only letters, numbers or underscore
Must not be a keyword
Have the following conventions:
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All uppercase letters are used for constants
Variable names are meaningful – thus, often multi-word
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Convention 1: alignment_sequence
Convention 2: AlignmentSequence
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C++ Basics – Data Types (1)
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3 basic data types
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Integer (int) – represent whole numbers
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long (32-bits same as default), short (16-bits)
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int y; // initialized to garbage
Ex 2: define an unsigned short integer variable
month initialized to 4 (April)
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signed (positive and negative, default), unsigned
(positive)
Ex 1: define an integer variable y
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System dependent
unsigned short int month = 4;
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C++ Basic – Data Types (2)
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Floating point – represent real numbers
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IEEE Standards
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Ex 1: define a single-precision floating-point
variable named error_rate and initialize to 3.5
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float error_rate = 3.5;
Ex 2: define a double-precision floating-point
variable named score and initialize it to .004
using scientific notation
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Single-precision (float, 32-bits)
Double-precision (double, 64-bits)
double score = 4e-3;
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C++ Basic – Data Types (3)
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Character – represent text
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ASCII – American Standard Code for Information
Interchange
Represents characters, numbers, punctuation, spacing
and special non-printable control characters
Example ASCII codes: 'A' = 65, 'B' = 66, … 'a' = 97, 'b'
= 98, '\n' = 10
Ex 1: define a character named AminoAcid and initialize
it to 'C'
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char AminoAcid = 'C';
char AminoAcid = 67;
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// equivalent
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C++ Basics – Arithmetic Operators
Operators
Example
int x, y=5, z=3;
+ add
x = y + z; x = 8
- subract
x = y – z; x = 2
* multiply
x = y * z; x = 15
/ divide
x = y / z; x = 1
% modulus/remainder x = y % z; x = 2
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C++ Basics – Auto Increment
and Decrement
x=3
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Pre-increment/decrement
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y = ++ x;
equivalent to
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y = --x;
equivalent to
x
y
x
y
=
=
=
=
x + 1; x
y
x;
x – 1; x
y
x;
=
=
=
=
4
4
2
2
y
x
y
x
=
=
=
=
y
x;
x + 1; x
y
x;
x – 1; x
=
=
=
=
3
4
3
2
Post-increment/decrement
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y = x++;
equivalent to
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y = x--;
equivalent to
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C++ Basics – Relational and
Logical Operators
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Relational operators
==
!=
>
>=
<
<=
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equal
not equal
greater than
greater than or
equal
less than
less than or equal
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Logical operators
&&
||
!
and
or
not
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C++ Basics – Relational
Operators
Assume x is 1, y is 4, z = 14
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Expression
Value
Interpretation
x<y+z
1
True
y == 2 * x + 3
0
False
z <= x + y
0
False
z>x
1
True
x != y
1
True
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C++ Basics – Logical
Operators
Assume x is 1, y is 4, z = 14
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Expression
Value
Interpretation
x<=1 && y==3
0
False
x<= 1 || y==3
1
True
!(x > 1)
1
True
!x > 1
0
False
!(x<=1 || y==3) 0
False
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if Statement
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if (expression)
Example:
action
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char a1 = 'A', a2 = 'C';
int match = 0;
if (a1 == a2) {
match++;
}
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if-else Statement
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if ( expression )
Example:
action 1
char a1 = 'A', a2 = 'C';
int match = 0, gap = 0;
if (a1 == a2) {
match++;
} else {
gap++;
}
else
action 2
Note: there is also the switch statement
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1-D Arrays
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char amino_acid;
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Defines one amino_acid as a character
1 cell
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char sequence[5];
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Defines a sequence of 5 elements of type
character (where each element may represent an
amino acid)
5 cells with
indices
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0
1
2
3
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Initializing Arrays
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char seq [5] = “ACTG”;
5 cells with
values
'A' 'C' 'T'
'G' '\0'
seq[0] = 'A'
seq[1] = 'C'
…
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float hydro[6] = {-0.2, 0, -0.67, -3.5, 2.8};
5 cells with
values
-.2
0
-.67 -3.5
2.8 0
hydro['A' - 'A'] = -.2 hydro['C' - 'A'] = -.67
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hydro[5] = 0
No initialization – each cell has “garbage” – unknown
value
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for Statement
for( expr1; expr2; expr3 )
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action
Expr1 – defines initial
conditions
Expr2 – tests for
continued looping
Expr3 – updates loop
Example
sum = 0;
for(i = 1; i <= 4; i++)
sum = sum + 1;
Iteration 1: sum=0+1=1
Iteration 2: sum=1+2=3
Iteration 3: sum=3+3=6
Iteration 4: sum=6+4=10
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while Statement
while (expression)
action
Example
int x = 0;
while(x != 3) {
/ 2
x = x + 1;
Infinite loop!
}
Iteration
Iteration
Iteration
Iteration
Note: skipping do while
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1:
2:
3:
4:
x=0+1=1
x=1+1=2
x=2+1=3
don’t exec
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C++ I/O streams - input
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Standard I/O input stream: cin
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Ex:
int x;
char c1, c2, c3;
cin >> x >> c1 >> c2 >> c3;
If the following input is typed: 23 a
bc
Then, x = 23, c1 = 'a', c2 = 'b', c3 = 'c'
(will ignore white spaces)
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C++ I/O streams - output
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Standard I/O output stream: cout
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Ex:
int x = 1;
char c1 = ‘#‘;
cout << “SoCalBSI is " << c1 << x << ‘!’ << endl;
The following output is displayed: SoCalBSI is #1!
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I/O Streams Usage
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Must include iostream header file
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#include <iostream>
There are ways to format the output to
specify parameters such as the width of
a field, the precision, and the output
data type
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Example: Amino Acid Search
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Write a program to count the number of
occurrences of an amino acid in a
sequence.
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The program should prompt the user for
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A sequence of amino acids (seq)
The search amino acid (aa)
The program should display the number of
times the search amino acid (aa) occurred
in the sequence (seq)
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Example: Amino Acid Search (2)
// This program will find the number of occurrences of an amino acid in a given sequence.
// Written By: Prof. Warter-Perez
// Date Created: April 16, 2002
// Last Modified: June 13, 2003
#include<iostream>
using namespace std;
#define MAX 42
void main () {
// Ring Finger protein 1
char seq[MAX] = "CPICLDMLKNTMTTKECLHRFCSDCIVTALRSGNKECPTC";
char aa;
int count = 0, i;
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Example: Amino Acid Search (3)
cout << "Enter search amino acid: "<< flush;
cin >> aa;
for (i = 0; i < MAX; i++) {
if (seq[i] == aa)
count++;
}
if(count == 1)
cout << "There was 1 occurrence ";
else
cout << "There were " << count << " occurrences ";
cout << "of amino acid " << aa << " in sequence " << seq << "." << endl;
}
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Steps to Creating a Visual C++
Project (Step 1)
To create a project
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Under File, select New
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Under Projects
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Select Win32 Console Application
Assign a Project name and Location for your project
Select Create new workspace
When prompted for type of console application,
select empty project
Click Finish
Click OK
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Steps to Creating a Visual C++
Project (Step 2)
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To add a C or C++ source file to the
project
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Under File, select New
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Under Files
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Select C++ Source File
Select Add to project (Project will be set to the
current project)
Assign a File name (use the default location
determined by the project)
Click OK (the source file will be displayed in the
editor window)
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Steps to Creating a Visual C++
Project (Step 3)
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Enter your program in the editor
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Notice that the editor has a color coding
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Also notice that it automatically indents
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Comments
Key words
Everything else
Don’t override!!
If doesn’t indent to proper location – indicates
bug
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Steps to Creating a Visual C++
Project (Step 4)
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To build your program
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Under Build
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In case of compile time errors or warnings,
they will be listed in the bottom window
(scroll up)
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Select Build project_name.exe
Double click on error or warning to find in
program
After fixing error (bug), rebuild following same
steps
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Steps to Creating a Visual C++
Project (Step 5)
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To execute your program
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First, create any necessary input files
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Under File, select New
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To run your program (can click ‘!’ icon, or)
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Under Files, select Text File
Assign File name and Location (default ok)
It is OK to add to project (default)
Click OK
Under Build, select Execute project_name.exe
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Programming Workshop #1
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Write a C++ program to compute the hydrophobicity
of an amino acid
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Program will prompt
the user for an
amino acid and will
display the
hydrophobicity
Program should
prompt the user to
continue
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A m in o A c id
A
C
D
E
F
G
H
I
K
L
M
N
P
Q
R
S
T
V
W
Y
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H y d ro p . V A L U E
1 .8
2 .5
- 3 .5
- 3 .5
2 .8
- 0 .4
- 3 .2
4 .5
- 3 .9
3 .8
1 .9
- 3 .5
- 1 .6
- 3 .5
- 4 .5
- 0 .8
- 0 .7
4 .2
- 0 .9
- 1 .3
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