chapter 3 ada dua bahagian.. bahagian 1 ialah Understanding Input.

dalam chapter 3 bahagian 1 tok, kita tauk apa ya input.. Input is any data and instructions entered into the memory of a computer. selain daripada maksud Input, kita juak tauk apa ya Input Devices.. contoh input devices ialah keyboard, mouse and other pointing devices; touch screen, pen input, other input for smartphones, game controllers, digital cameras, voice input, video input, scanners and reading devices, biometric input and terminals.

there are several input devices are available to assist physically challenged users.
  * key guard
  * keyboards with larger keys
  * on-screen keyboard
  * various pointing devices
  * head-mounted pointer
  * gesture recognition
  * computerized implant devices

chapter 3 bahagian 2 ialah Understanding Output..
Apa itu Output??
  + Output is data that has been processed into a useful form.
  +  Output device is any type of hardware component that conveys information to one or more people.. dalam output device terbahagi kepada beberapa bahagian.. that are display devices, printers, speakers, earphone and earbuds, data projectors, interactive whiteboards, force feedback game controllers and tactile output.

Dalam display devices ada LCD monitor or LCD screen, plasma monitor, and CRT monitor.  Printer juga terbahagi kepada 2 jenis iaitu impact and nonimpact printer.. nonimpact printer is forms characters and graphic on a piece of paper without actually striking the paper. Impact printers form characters and graphics on a piece of paper by striking a mechanism against an inked ribbon that physically contacts the paper.  Speakers, earphone and earbuds is an audio output device produces music, speech or other sounds.  voice output occurs when you hear a person's voice or when the computer talks to you through the speakers.

that's all in chapter 3 (understanding input and output)