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BIEN 001 Introduction to Biomedical Engineering Methods Module 1:Introduction to Computers,

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BIEN 001 Introduction to Biomedical Engineering Methods

Module 1:Introduction to Computers,

Flowcharting and Programming in C

Roger H. Johnson, [email protected]

September 5, 2000

Objectives:

• Introduction to Computers

and Computing Environment at Marquette.

• Develop problem-solving strategies through flow charting.

• Introduction to program development environment.

• Introduction to C language programming.

• Develop two real C programs and run them.

Lectures 1-2:

• Computing History

• Computer Constituents

• Evolution of Programming

• Essential Programming Steps

• Syntax

• Develop Two Programs in C

• • Computing History

• Blaise Pascal and the mechanical adder

Pascal was a French genius and mathematician

who died young after religious mania.

In 1642 he invented a mechanical calculator to assist

in the adding of long columns of numbers in his

father’s tax office.

His most important writing is Thoughts on Religion.

• Gottfried Wilhelm Leibnitz’ adder/multiplier

German invention of 1673 (or1694)

which used stepped-gear-wheels.

• Joseph Jacquard and his pasteboard loom cards

1812: Pasteboard card read by the loom.

Hole pattern determined thread combinations.

• Charles Babbage and his analytical engine

1830’s: First the Difference Engine, which would have been

two tons of brass, steel and pewter clockwork.

1840: Then the Analytical Engine which could decide between

two courses of action. Steam-engine-powered, would

read punched cards, compute, request cards with bell.

• Herman Hollerith and the census device

1890: Used punched cards to process census information

and speed tabulation.

• Howard Aikens and the Mark I

1944: Harvard Mark I. Used mechanical counters and

electromagnetic relays to control its operation.

• John Mauchly and John Eckert and the Eniac

1946: Huge vacuum-tube computer; part of the war effort.

Ballistic computations and code-breaking.

• John Backus and FORTRAN

1954: First inovation to translate human-intelligible

language into machine language.

• Kernighan and Ritchie and C

1970’s: Dominant language in scientific programming today.

FORTRAN 77 persists and other language, such as Pascal,

Basic, and Cobol are used in niches.

Input

Output

CPU

Arithmetic and

logical unit

Control

unit

• Computer Constituents

CPU = central processing unit

= control unit + arithmetic and logical unit

Memory

Input

Output

Memory

Control Unit: Controls timing and directs all

computer operations.

Arithmetic Logic Unit: Makes all decisions

and performs calculations.

Memory: Stores instructions and data live

within the computer.

Input: Devices which input information into memory.

Output: Devices which print or display data from

memory.

• Evolution of Programming

Machine language: sequence of zero’s and one’s

= “binary string”.

(refer to handout on binary number system)

Assembly language: uses keywords to stand for

sequences of zero’s and one’s:

“ADD” = 0010001110001111

One keyword is one line of code

is one binary string is one instruction.

Compiler level: (“high-level” resembles English)

e.g. C = A + B

for(i=1;i<5000;i++)

{.....

One line of code can contain several words and

require many machine language instructions.

Object oriented: New “pictorial” method we

won’t get into.

• Essential Programming Steps

1) A clear statement of the problem:

Decide what it is you really want to do. Helps to

decide if computer is really the way to do it.

2) A rough or general solution algorithm:

Write down in brief format the steps required

to solve the problem.

3) A refined algorithm of the solution:

More detailed sequence of steps.

4) A flowchart of the full solution process:

Draw a block diagram or “flow diagram”

of the computer program.

5) Computer language coding + documentation:

A line-by-line written version of computer code.

6) Creation of a computer file of the coding:

Type in the code using a text editor.

7) Compile and run the file:

Type a command which creates the object file

and the machine language version of code.

8) Obtain sufficient output to test the full

solution algorithm for generality.

An algorithm is a description of a solution

method. Synonyms are “procedure”, “method”,

“technique” or “(set of) rule(s)”.

In the programming context,

an algorithm must possess these characteristics:

• It must end after a finite number of steps.

• It must be describable by a finite sequence of

steps or instructions.

• It must be capable of dealing with all members

of a particular class of problem.

A flowchart is a pictorial representation of an

algorithm.

Flowcharts are sometimes called “block diagrams”

or “flow diagrams”.

A flowchart is a schematic of the logic used

in problem solution and, properly used,

should aid in the development

of a sound logical approach.

A completed flowchart should exactly represent

the sequence of steps coded into the program,

and can help avoid a number of common

programming errors.

Flowchart Symbols:

Casanova Flowchart Example:

Meal-ordering Flowchart:

Flowchart for Tuition Computation:

Tuition Computation Flowchart with Nested

Decision Loops:

Tuition Computation Flowchart with Termination:

Tuition Computation with Termination:

Decision with a Three-way Branch:

Counter for Loop

Termination:

Balance Computation

with Termination:

Example used in Lab 1:

C program to solve two linear equations

with two unknowns.

Of the several methods to solve this problem,

we choose to solve for x and y

by the use of determinants.

e.g.

x + 2y = 5

5x - y = 3

For the general case:

Ax + By = C

Dx + Ey = F

It must be borne in mind that division by zero

is not allowed. This would happen with parallel lines:

x + 2y = 5

3x + 6y = 10

and would also occur with coincident lines:

x + 2y = 5

-2x -4y = -10

Steps Required in Writing the Program:

Steps 1 through 4 should be done

before you come in to lab:

1) Statement of the problem.

What we just did.

2) General Algorithm:

an overall solution process

which should consist of numbered steps.

3) Refined Algorithm:

expand the general algorithm;

add major variable names or formulas;

add solution detail to the plan.

4) Flow Chart: give complete control process;

supply minor control variables;

use algorithm-defined variables and formulas;

think through “what will happen if?”.

5) Program Coding: uses all of the above;

supplies the input and output

detail and documentation;

provides adequate comments.

Step 2) Example of General Algorithm:

1) Open data file.

2) Repeatedly

3) read coefficients

4) write system

5) calculate determinants

6) test for output case, process and output

7) End.

Example of refined algorithm:

1.1 Query for input filename

1.2 Open input file

2.1 For all data

3.1 Read coefficients A, B, C, D, E, F

3.2 If end of data, go to 6.9.

4.1 Write system: Ax + By = C

Dx + Ey = F

5.1 Den = AE-DB

5.2 Xnum = CE-FB

5.3 Ynum = AF-DC

6.1 If Den !=0, go to 6.5

6.2 If Xnum=0, write “no unique solution”

6.3 If Ynum !=0, write “no solution”

6.4 Go to 3.1

6.5 X = Xnum/Den

6.6 Y = Ynum/Den

6.7 Write “‘x =‘ X; ‘y=‘ Y.”

6.8 Go to 3.1

6.9 End.