FALL 2001 ICOM 4015 - Lecture 1 1

ICOM 4015 Advanced Programming

Lecture 1

Computer/Human Interaction

Readings: LMM 2.3 & 3.3

Prof. Bienvenido Velez

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Computer/Human InteractionOutline

• Output Streams

• Input Streams

• Formatting output

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Layered Software Design

Library/Component

Appl Programming Interface (API)

GUI

Text-basedInteractiveInterface

Text-basedBatch

Interface

ICOM 4015

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Example 1Simple output program

*********************************************

#include <iostream>

main() {

for(int i=0; i<10; i++) { for(int j=0; j<i; j++) { cout << "*"; } cout << endl; }}

example1.cc

output

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OutputStream insertion operator

cout << expression

outputstream

streaminsertionoperator

argumentexpression

returns an output stream

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Example 2

0 stars* 1 stars** 2 stars*** 3 stars**** 4 stars***** 5 stars****** 6 stars******* 7 stars******** 8 stars********* 9 stars

#include <iostream>

main() {

for(int i=0; i<10; i++) { for(int j=0; j<i; j++) { cout << "*"; } cout << " " << i << " stars"; cout << endl; }}

example2.cc

output

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InputStream extraction operator

cin >> variable

inputstream

streamextractionoperator

argumentexpression

returns an input stream

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Example 3

[bvelez@amadeus] ~ >> example3Enter number of rows: 7 0 stars* 1 stars** 2 stars*** 3 stars**** 4 stars***** 5 stars****** 6 stars[bvelez@amadeus] ~ >>

#include <iostream>

main() {

int entered; cout << “Enter number of rows: "; cin >> entered; for(int i=0; i<entered; i++) { for(int j=0; j<i; j++) { cout << "*"; } cout << " " << i << " stars"; cout << endl; }} example3.cc

shell

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Example 4

[bvelez@amadeus] ~ >> example4Enter number of rows(-1 to end): 5 0 stars* 1 stars** 2 stars*** 3 stars**** 4 starsPlease enter an integer (-1 to end): -1[bvelez@amadeus] ~ >>

#include <iostream>

main() { while (true) { cout << " Enter number of rows (-1 to end): "; int entered; cin >> entered; if (entered == -1) { break; } for(int i=0; i<entered; i++) { for(int j=0; j<i; j++) { cout << "*"; } cout << " " << i << " stars"; cout << endl; } }}

example4.cc

shell

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Example 5I/O Manipulators

extern "C"{#include <stdlib.h>}#include <iostream>#include <iomanip>

main() { int rows = 0; cout << "Please enter number of rows: "; cin >> rows; int columns = 0; cout << "Please enter number of columns: "; cin >> columns; unsigned int seed = 511; srand (seed); for (int i=0; i<rows; i++) { for (int j=0; j<columns; j++) { cout << setprecision(4) // prints only 4 decimal digits << setw(10) // prints each number is field of 10 spaces << setfill('*') // fills empty spaces with '*' << rand()/float(RAND_MAX) << " "; } cout << endl; }}

[bvelez@amadeus] ~/icom4015/lec2 >> ./example5Please enter number of rows: 5Please enter number of columns: 5****0.6858 ****0.4712 ***0.08415 ****0.7637 ****0.5106****0.2954 *****0.756 ****0.9517 ****0.9653 ****0.1655****0.7404 ****0.7084 ****0.2605 ****0.9858 ****0.8554****0.5025 *****0.583 ****0.5728 ***0.03958 ***0.02455****0.6029 ****0.7031 ****0.2055 ****0.6303 ****0.5802[bvelez@amadeus] ~/icom4015/lec02 >>

example5.cc

shell

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Example 6Computing Statistics in One Pass

[bvelez@amadeus] ~/icom4015/lec02 >> example6Please enter a number (-1 to end): 5Please enter a number (-1 to end): 6Please enter a number (-1 to end): 7Please enter a number (-1 to end): 8Please enter a number (-1 to end): -1Statistics:Average: 6.5Count: 4Max: 8Min: 5[bvelez@amadeus] ~/icom4015/lec02 >>

#include <iostream>#include <iomanip>

main() { float nextNumber; float sum = 0; float count = 0; float max; float min; bool firstTime = true; while (true) { cout << "Please enter a number (-1 to end): "; cin >> nextNumber; if (nextNumber == -1) { break; } sum += nextNumber; count++; if (firstTime) { max = nextNumber; min = nextNumber; firstTime = false; } else { max = (max < nextNumber) ? nextNumber : max; min = (min > nextNumber) ? nextNumber : min; } } cout << "Statistics:" << endl; cout << "Average: " << sum / count << endl; cout << "Count: "<< count << endl; cout << "Max: " << max << endl; cout << "Min: " << min << endl;}

example6.cc

shell

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Example 6With Input redirection

[bvelez@amadeus] ~/icom4015/lec02 >> example6 < example6.txtPlease enter a number (-1 to end): Please enter a number (-1 to end): Please en\ter a number (-1 to end): Please enter a number (-1 to end): Please enter a num\ber (-1 to end): Statistics:Average: 6.5Count: 4Max: 8Min: 5[bvelez@amadeus] ~/icom4015/lec02 >>

5678-1

example6.txt

shell

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Example 6With Input/Output redirection

[bvelez@amadeus] ~/icom4015/lec02 >> example6 < example6.txt >example6.out[bvelez@amadeus] ~/icom4015/lec02 >>

5678-1

shell

Please enter a number (-1 to end): Please enter a number (-1 to end): Please en\

ter a number (-1 to end): Please enter a number (-1 to end): Please enter a num\

ber (-1 to end): Statistics:

Average: 6.5

Count: 4

Max: 8

Min: 5

example6.txt

example1.out

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Summary of ConceptsFundamentals

• Computer-Human Interaction is a subarea of study in its own right within Computer Science

• One pass computing - Process input as you read it. Less memory required to store data. Limited algorithmic expressiveness.

• Input redirection allows me to store input input in a file. Helpful for debugging because don’t need to re-enter test input every time.

• Output redirection allows me to dump the output of a program to a file. A file can be examined, saved, emailed, …

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Summary of ConceptsLanguage Issues

• Language issues– Must #include <iostream>– Stream insertion operators can be

chained. Example:(cout << expr1) << expr2

– Stream extraction operator can be chained. Example:

(cin >> var1) >> var2

– I/O manipulators provide fine-grain control over format of output

• setprecision – decimal digits• setw – width of output field• setfill – filler for empty space