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Learn it your way
A short class with Sarah and her students. The other ways are under More.
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When you type a capital A on a keyboard, what does the computer actually receive?
The letter A?
Not quite. The keyboard detects which key closed its circuit and sends a code. The operating system turns that code into a character, which is stored as the number 65, in binary.
So every input device is really a converter, from something physical into numbers?
Exactly. A microphone does the same with sound, but sound is a smooth analog wave, so an analog-to-digital converter measures it thousands of times a second.
And how does the computer know what the device is sending?
A device driver tells the operating system how to understand that device's data. Remember the four steps: sense, convert, transfer, interpret.
Many entrance and competitive exams use answer sheets with filled bubbles that are checked by a machine. Which device do you think it is?
OMR, because it only checks whether a bubble is marked or not.
Right. OCR is different: it recognises the actual letters in a scanned page and turns them into editable text.
Then why do banks use MICR for cheques instead of OCR?
Because the characters are printed in magnetic ink. They can be read even when a stamp or signature covers them, and they are hard to forge.
And at a shop counter the barcode reader enters the product code, so the cashier never types the price.
Yes. All of these are direct data entry devices: fast, accurate and ideal for large volumes of data.
A school wants to record attendance for 1,500 students every morning. Typing names would be slow. What would you suggest?
A fingerprint scanner or ID cards with barcodes at the gate.
Good. Now think of a student who cannot see the keyboard. What could help?
Voice input with a microphone, or a Braille keyboard.
Both are used. So when choosing an input device, ask what kind of data it is, how much there is, how accurate it must be and who will use it.
So the best device depends on the job, not on which device is newest.
Exactly right.
They convert physical actions, sounds, images and marks into binary data for the computer.
Sense, convert (with an ADC for analog signals), transfer through a port, interpret with a device driver.
Keyboards, pointing devices, scanning and recognition devices, audio and video devices, biometric devices and sensors, and touchscreens.
OCR, OMR, MICR and barcode readers read data straight from documents or products, quickly and accurately.
They are both input and output devices; resistive screens respond to pressure and capacitive screens to a finger's charge.
Match the device to the type and volume of data, the accuracy needed, the cost and the user.
At a supermarket billing counter, a barcode reader enters each product's code in a fraction of a second, so prices are fetched without typing and without typing mistakes.
In many entrance and competitive examinations, multiple-choice answer sheets are marked by OMR, which checks thousands of sheets far faster than people could.
In a Java program, keyboard input arrives through System.in, the standard input stream, which is usually connected to the keyboard; type two numbers and the program adds them:
import java.util.Scanner;
public class KeyboardInput {
public static void main(String[] args) {
// System.in is the standard input stream, usually the keyboard
Scanner sc = new Scanner(System.in);
System.out.println("Enter two whole numbers:");
int a = sc.nextInt();
int b = sc.nextInt();
System.out.println("Sum = " + (a + b));
}
}Once typed characters reach memory, each is stored as a number; this program prints the code and binary form of the characters H, i and 5 (72, 105 and 53):
public class KeyCodes {
public static void main(String[] args) {
String typed = "Hi5"; // three keys typed on the keyboard
for (int i = 0; i < typed.length(); i++) {
char ch = typed.charAt(i);
System.out.println(ch + " is stored as " + (int) ch
+ " = binary " + Integer.toBinaryString(ch));
}
}
}Press it, point it, scan or speak, the input turns it into bits we seek.
A cheque, an answer sheet and a packet of biscuits walk into a bank, an exam hall and a shop. The cheque is read by MICR, the answer sheet by OMR and the biscuits by a barcode reader, and nobody types a single digit.
Marks, Characters, Cheques: OMR reads Marks, OCR reads Characters and MICR reads Cheques.
S.C.T.I.: Sense, Convert, Transfer, Interpret, the four steps of every input.
Term
What does an analog-to-digital converter do?
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Term
OMR or OCR: which one checks filled bubbles on an answer sheet?
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Term
Why do banks use MICR on cheques?
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Term
What is a device driver?
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Term
Resistive or capacitive: which touchscreen works with a gloved hand?
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Hardware that captures data or instructions from a user or the surroundings and sends them to the computer.
A circuit that measures a continuous signal, such as sound, many times a second and turns each measurement into a binary number.
A small program that lets the operating system understand and control a particular hardware device.
Software that recognises printed characters in a scanned image and converts them into editable text.
Technology that detects marks, such as filled bubbles, in fixed positions on a form.
Technology that reads characters printed in magnetic ink, used on bank cheques.
An input device that identifies a person from a unique body feature, such as a fingerprint, iris or face.
Input in which a device reads data straight from a source, such as a barcode or form, without anyone typing it.
Input devices capture data and instructions from people and their surroundings, such as key presses, pointer movements, sounds, images and marks on paper, and turn them into binary data the computer can process.
Input is the first stage of the input-process-output cycle. This lesson explains how an input device senses a physical action, converts it into electrical signals and passes it to the computer through a port and a device driver. It then classifies input devices into keyboards, pointing devices, scanning and recognition devices (scanner, OCR, OMR, MICR, barcode reader), audio and video devices, biometric devices and sensors, and touchscreens, and shows how to choose the right device for a task.
An input device is any hardware that lets a person, or the surroundings, give data and instructions to a computer. A computer can work only with binary numbers (0s and 1s), but the world gives it key presses, hand movements, sounds, pictures and pencil marks. The job of an input device is to turn these physical things into binary data.
Every input device, simple or complex, works in four steps:
These devices read data straight from a document or object, so nobody has to type it. They are fast and accurate for large volumes of data.
A touchscreen is both an output device (it shows the picture) and an input device (it senses touch). A resistive touchscreen has two flexible layers that touch when pressed, so it works with a finger, a gloved hand or any pointer. A capacitive touchscreen senses the small change in electric charge caused by a finger, and it supports multi-touch gestures such as pinch-to-zoom; most smartphones use this type.
The right device depends on the kind of data, how much of it there is, how fast and how accurately it must be entered, the cost and the person using it. Direct data entry devices such as barcode readers, OMR and MICR are far faster and more accurate than typing when there is a lot of data. Voice input and Braille keyboards help users with visual or movement difficulties.