03_GENN004m_InputOutput

7/29/2019 03_GENN004m_InputOutput

1/7

GENN004: Introduction to Computers 09-Feb-

Input and Output

Input and Output

Algorithms

Input and Output Functions

Outline

Algorithms

Input Function

Controlling Output


2/7


Input and Output

Algorithms

Before writing any computer program, it is usefulto first outline the steps that will be necessary.

An algorithm is the sequence of steps needed tosolve a problem.

In a modular approach to programming, theproblem solution is broken down into separatesteps, and then each step is further refined untilthe resulting steps are small enough to be

manageable tasks. This is called the top-downdesign approach.

Algorithm Example

Calculating the area of a circle

1. Get the input: the radius

2. Calculate the result, the area

3. Display the output

For most programs, the basic algorithm

1. Get the input(s)2. Calculate the result(s)

3. Display the result(s)


3/7


Input and Output

Input Function

MATLAB allows you to prompt for inputinteractively

This is through the input function:

input(prompt_string)

input(prompt_string, options_string)

prompt_stringtells MATLAB what text todisplay while waiting for a user to type something

options_stringlets you specify how

MATLAB should interpret the input

Use s to indicate the input is a string

Input Examples

Try

>> radius=input(Enter the radius:)

>> user_name = input(What is your name? \n, s)

>> user_age = input(What is your age? \n)


4/7


Input and Output

Controlling Output

MATLAB gives you a number of ways to

control how output is displayed

Changing how numbers are displayed does

not change the precision of the underlying

computations

To change the default precision of echoed

numbers in the Command Window, use theformat command

format Optionsformat Description Example

short 4 digits after decimal 3.1416

long 14 digits after decimal 3.141592653589793

short e 5 digits plus exponent 3.1416e+000

short g 5 digits,with or without exponent 3.1416

long e 15 digits plus exponent 3.141592653589793e+000

long g 15 digits, with or without exponent 3.14159265358979

bank dollars and cents 3.14

hex 4-bit hexadecimal 400921fb54442d18

rat approximate ratio of small integers 355/113

Try

>> x=pi;

>> format short, x

>> format long, x

>> format bank, x


5/7


Input and Output

fprintf function

fprintf can be used to control how output isdisplayed

fprintf(format,data)

fprintf(format,data1,data2, )

format is a string specifying how to display the data

data, dataxare variables or values (either scalar orarray)

Example:

fprintf(pi:%d pi rounded: %1.0f\n,pi,pi)

fprintf function

The %d characters in the format string arecalled conversion characters

Each conversion character is a data place-holder in the format string

Each conversion character has a number of

optional formatting parameters These parameters go between the % and the

conversion character (d, f, i, etc.)


6/7


Input and Output

fprintf function

%-8.2fNumber insertion

marker

Optional Flag

indicating positioning

inside the field

Field width &

decimal precision

Conversion

character

fprintf function%? Results

%d displayvalue in standard decimal notation

%e display value in exponential form

%f display value in fixed(floating)-point form

%g display as %e or %f, whichever is shorter

%s display a string of characters (not used with numbers)

To display a %, use %% in fprintfs format

For complete list of options, use >> help fprintf

Try

>> x=3.1253;

>> fprintf(x= %.0f, %10.5f, %-10.2f, %%\n,x,x,x);

>> fprintf(x= %.0f, %10.5f, %-10.1f, \n %%,x,x,x);


7/7


Input and Output

Test it out!

Write a script to take the radius of a circle as

an input from the user, calculate the area,

then print the area.

Sample Input/Output

This program calculates the area of a circle

Enter the radius: 5

The area of a circle with radius 5 equal to 78.54

>>

clc;

fprintf('This program calculates the area of a circle\n');

r=input('Enter the radius:');

a=pi*r^2;

fprintf('The area of a circle with radius %1.0f equal to %10.2f\n',r,a);

03_GENN004m_InputOutput

Documents

Transcript of 03_GENN004m_InputOutput